C
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IS
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Fo
rm

4

Form 4
CHEMISTRY

RM10.50

FT714001

ISBN 978-967-2375-43-2

DUAL   LANGUAGE   PROGRAMME
RUKUN NEGARA
Bahawasanya Negara Kita Malaysia

mendukung cita-cita hendak;

Mencapai perpaduan yang lebih erat dalam kalangan
seluruh masyarakatnya;

Memelihara satu cara hidup demokrasi;

Mencipta satu masyarakat yang adil di mana kemakmuran negara
akan dapat dinikmati bersama secara adil dan saksama;

Menjamin satu cara yang liberal terhadap
tradisi-tradisi kebudayaannya yang kaya dan pelbagai corak;

Membina satu masyarakat progresif yang akan menggunakan
sains dan teknologi moden;

MAKA KAMI, rakyat Malaysia,
berikrar akan menumpukan

seluruh tenaga dan usaha kami untuk mencapai cita-cita tersebut
berdasarkan prinsip-prinsip yang berikut:

KEPERCAYAAN KEPADA TUHAN
KESETIAAN KEPADA RAJA DAN NEGARA

KELUHURAN PERLEMBAGAAN
KEDAULATAN UNDANG-UNDANG
KESOPANAN DAN KESUSILAAN

(Sumber: Jabatan Penerangan, Kementerian Komunikasi dan Multimedia Malaysia)
Writers
Lim Kuok Chen

Dr. Nur Jahan Ahmad
Dr. Chua Kah Heng

Wong Choy Wan
Lee Sze Yien

Translators
Dr. Chan Siok Gim

Lim You Sie
Lee Chwee Neo

Editors
Amalina binti Ahmad

Khairul Maisarah binti Kahar

Designer
Loh Hong Seng

Illustrator
Ai Khen bin Wong

PENERBITAN PELANGI SDN. BHD.

KURIKULUM STANDARD SEKOLAH MENENGAH

2019

4
FORM

CHEMISTRYCHEMISTRY
KEMENTERIAN
PENDIDIKAN
MALAYSIA

The publication of this textbook involves
cooperation from various parties. Our
wholehearted appreciation and gratitude goes
out to all involving parties.

• Committee members of Penyemakan
Naskhah Sedia Kamera, Educational
Resources and Technology Division,
Ministry of Education Malaysia

• Officers in Educational Resources and
Technology Division and the Curriculum
Development Division, Ministry of
Education Malaysia

• R. Weller/Cochise College

KPM2019 ISBN 978-967-2375-43-2

First Published 2019
© Ministry of Education Malaysia

All Rights Reserved. No part of this book may
be reproduced, stored in any retrieval system or
transmitted in any form or by any means, either
electronic, mechanical, photocopying, recording
or otherwise, without the prior permission of the
Director General of Education Malaysia, Ministry
of Education Malaysia. Negotiation is subject to
the calculation of royalty or honorarium.

Published for
Ministry of Education Malaysia by:
Penerbitan Pelangi Sdn. Bhd.
66, Jalan Pingai, Taman Pelangi,
80400 Johor Bahru,
Johor Darul Takzim.

Layout and typesetting:
Penerbitan Pelangi Sdn. Bhd.
Font type: Minion Pro
Font size: 11 pt.

Printed by:
The Commercial Press Sdn. Bhd.
Lot 8, Jalan P10/10,
Kawasan Perusahaan Bangi,
Bandar Baru Bangi,
43650 Bangi,
Selangor Darul Ehsan.

Book’s Serial No: 0176
ACKNOWLEDGEMENTS
Introduction	 v

Laboratory	Rules	and	Safety	Measures viii

Themes	  1

Introduction	to	Chemistry	1
Chapter

2
 1.1 Development in Chemistry Field and Its Importance

in Daily Life 4
	 1.2	 Scientific	Investigation	in	Chemistry	 8
	 1.3	 Usage,	Management	and	Handling	of
	 	 Apparatus	and	Materials	 11
 Achievement	Test	1 20

Matter	and	the	Atomic	Structure	2
Chapter

22
	 2.1	 Basic	Concepts	of	Matter	 24
	 2.2	 The	Development	of	the	Atomic	Model	 29
 2.3 Atomic Structure 32
 2.4 Isotopes and Its Uses 37
 Achievement	Test	2 40

The	Mole	Concept,	Chemical	Formula	and	Equation3
Chapter

42
	 3.1	 Relative	Atomic	Mass	and	Relative	Molecular	Mass		 44
	 3.2	 Mole	Concept		 49
	 3.3	 Chemical	Formula		 59
	 3.4	 Chemical	Equation	 69
 Achievement	Test	3	 76

The	Periodic	Table	of	Elements	4
Chapter

78
	 4.1	 The	Development	of	the	Periodic	Table	of	Elements	 80
	 4.2	 The	Arrangement	in	the	Periodic	Table	of	Elements	 82
	 4.3	 Elements	in	Group	18	 84
	 4.4	 Elements	in	Group	1	 87
	 4.5	 Elements	in	Group	17		 92
	 4.6	 Elements	in	Period	3	 96
	 4.7	 Transition	Elements	 101
 Achievement	Test	4	 106

ContentsContents

iii
Acid,	Base	and	Salt6
Chapter

134
	 6.1	 The	Role	of	Water	in	Showing	Acidic	and

Alkaline	Properties	 136
	 6.2	 pH	Value	 143
	 6.3	 Strength	of	Acids	and	Alkalis	 149
	 6.4	 Chemical	Properties	of	Acids	and	Alkalis		 152
	 6.5	 Concentration	of	Aqueous	Solution	 158
	 6.6	 Standard	Solution	 162
	 6.7	 Neutralisation	 167
	 6.8	 Salts,	Crystals	and	Their	Uses	in	Daily	Life		 174
	 6.9	 Preparation	of	Salts	 178
	 6.10	 Effect	of	Heat	on	Salts		 190
	 6.11	 Qualitative	Analysis		 197
 Achievement	Test	6	 216

Rate	of	Reaction7
Chapter

218
	 7.1	 Determining	Rate	of	Reaction	 220
	 7.2	 Factors	Affecting	Rate	of	Reactions	 230
	 7.3	 Application	of	Factors	that	Affect	the	Rate	of

Reaction	in	Daily	Life	 240
 7.4 Collision Theory 243
 Achievement	Test	7 250

Manufactured	Substances	in	Industry	8
Chapter

252
	 8.1	 Alloy	and	Its	Importance	 254
	 8.2	 Composition	of	Glass	and	Its	Uses	 260
	 8.3	 Composition	of	Ceramics	and	Its	Uses	 262
	 8.4	 Composite	Materials	and	Its	Importance	 265
 Achievement	Test	8 273
The	Periodic	Table	of	Elements	 275
The	Data	Table	of	Elements		 276
Glossary  277
References	 	 279
Index	 	 	 280

Chemical	Bond	5
Chapter

108
	 5.1	 Basics	of	Compound	Formation	 110
 5.2 Ionic Bond 111
 5.3 Covalent Bond 114
	 5.4	 Hydrogen	Bond	 117
	 5.5	 Dative	Bond	 120
	 5.6		 Metallic	Bond	 121
	 5.7	 Properties	of	Ionic	Compounds	and

Covalent Compounds  122
 Achievement	Test	5 132

iv
This Kurikulum Standard Sekolah Menengah (KSSM) Form 4 Chemistry textbook is written
based on Form 4 Chemistry Dokumen Standard Kurikulum dan Pentaksiran (DSKP) that is
prepared by the Ministry of Education Malaysia. In order to successfully implement and fulfil
the needs of DSKP, this book is written based on three domains: Knowledge, Skills and Values
through methods of inquiry. There are four themes to be discussed, namely the Importance of
Chemistry, Fundamentals of Chemistry, Interaction between Matter and Industrial Chemistry.
  This book is equipped with various special features that focus on instilling Science,
Technology, Engineering and Mathematics (STEM), thinking skills, scientific skills and
computational thinking so that students can master skills that are needed for the 21st century
and to be individuals who are science-oriented. Special features in this book are as follows:

Chemicals in daily life

Chemicals in Daily Life

All substances around us are made up of chemicals. The activities

that we carry out daily involve chemical reactions as well. Figure 1.2

shows the chemicals commonly used in foods, medicine, agriculture

and industries.

Drugs contain

chemicals

http://bit.
ly/2Mx4M7B

Activity 1.2

Collecting and interpreting the origin of the word chemistry and

its meaning

1. Carry out the Think-Pair-Share activity.

2.  Surf the Internet or refer to reading materials from various printed media to gather information

and discuss the following issues

(a) Origin of the word chemistry

(b) Meaning of chemistry

3. Present your group discussion results in multimedia form in front of your class.

Figure 1.2 Commonly used chemicals

Food

• Preservatives

•	 Colouring
•	 Flavouring
•	 Antioxidant

•	 Stabilizers

Agriculture

•	 Herbicide
•	 Pesticide
•	 Fungicide
•	 Fertiliser
•	 Hormone

Industry

•	 Paint
•	 Polymer
•	 Glass
•	 Ceramic
•	 Detergent
•	 Colouring
•	 Alloy

Medicine

•	 Antibiotic
•	 Antiseptic
•	 Vitamin
•	 Chemotheraphy

•	 Analgesic

Herbicide

Century
Skills21st

5

CHAPTER 1
Introduction to Chemistry

Applications of Neutralisation in Daily Life

Figure 6.31 shows the application of neutralisation for a variety of uses in daily life.

Neutralisation reaction is also applied in the production of fertilisers such as urea, potassium

sulphate, K2SO4, ammonium nitrate, NH4NO3 and others. For example, urea can be produced from

the neutralisation reaction between ammonia and carbon dioxide. How about other fertilisers?

Try to give the acids and alkalis involved in the production of that fertiliser.

Activity 6.11
Solving problems on soil fertility using suitable

fertilisers

1. Carry out this activity in groups.

2. Study the following problem statement:

Apart from treating acidic soil, fertilisers need to be added to soil to replace nutrients

such as nitrogen, potassium and phosphorus that have been absorbed by plants. There is a

variety of fertilisers in the market. Which fertilisers are suitable for plants?

3. Gather information concerning the problem given above.

(a) What type of crops were planted?

(b) What are the type of elements required by the crops?

(c) Identify the fertiliser that is suitable for the crops by considering the percentage of

elements such as nitrogen, phosphorus, and other needs, fertiliser cost and the quantity

needed for the area.

4.  Present your group findings in a multimedia presentation.

STEM CT

Medicine

Weak alkali in the
shampoo neutralises
acid on hair.

AgricultureHair health Dental health

Toothpaste contains a
base that neutralises
lactic acid produced by
bacteria in our mouth.

Milk of magnesia Mg(OH)2
relieves gastric pain by
neutralising the excessive
hydrochloric acid in
the stomach.

Milk of
Magnesia

Shampoo

Slaked lime, Ca(OH)2
which is alkaline, is used
to treat acidic soil.

T
O

O
T
H

P
A

S
T
E

M

e

n

y

e

g

a

r

k

a

n

Figure 6.31 Applications of neutralisation in daily life

Century
Skills21st

169

Acid, Base and Salt CHAPTER 6

21st Century Skills
Activities that involve 21st century skills:
• Thinking & problem-solving skills
• Interpersonal and intrapersonal skills
• Information and communication skills

Computational Thinking
Activities that involve computational thinking:
• Decomposition • Abstraction
• Pattern recognition • Algorithm
• Logical reasoning • Evaluation

STEM (Science, Technology, Engineering and Mathematics)
Activities that involve project-based learning through STEM
approach. STEM approach is based on teaching and learning
that applies knowledge, skills and STEM values through inquiry,
daily problem solving, environment, as well as local and global
communities.

21st Century Learning Activities
Various activities that emphasise student-centered
learning based on Higher Order Thinking
Skills (HOTS).

Information in the QR code on the front cover:
• Explanations of book themes
• Authors biodata
• Updated information and facts (if any)

CT

STEM

IntroductionIntroduction

Century
Skills21st

v
1. What new knowledge have you learned in Manufactured Substances in Industry?
 2. Which is the most interesting subtopic in Manufactured Substances in Industry? Why?
 3. Give several examples of application of Manufactured Substances in Industry in daily life.
 4. Rate your performance in Manufactured Substances in Industry on a scale of 1 to 10;
  1 being the lowest and 10 the highest. Why would you rate

yourself at that level?
 5. What can you do to improve your mastery in Manufactured

Substances in Industry?

https://bit.ly/
2RoRBJi

Achievement 8

1. The addition of coke (carbon) in the extraction process of iron is to remove oxygen from
iron ore. The iron and carbon mixture will form steel. Table 1 shows two types of steel with
different percentage of carbon.

Table 1

Steel Carbon %
Cast iron 4.0
High-carbon steel 0.8

(a) Cast iron is brittle whereas high-carbon steel is hard and strong. Based on Table 1,
calculate the percentage of carbon that must be removed from cast iron to produce
high-carbon steel.

(b) Stainless steel is produced from a mixture of chromium, nickel and carbon.
(i) State the percentage of chromium, nickel and carbon in stainless steel.
(ii) Stainless steel is suitable to be used to make high quality knife blades. Explain.

2. Lead crystal glass can be used to make spectacle lenses.
(a) What is the composition of lead crystal glass?
(b) Explain the advantages and disadvantages of using lead crystal glass to make
 spectacle lenses.

(c) Nowadays, spectacle lenses are made from polycarbonate polymer. The properties of
polycarbonate are as follows:

•	 Low	density	and	easily	moulded
•	 Absorb	UV	rays	and	is	very	transparent
•	 High	impact	resistance

You need a pair of new spectacles. Will you choose lenses made from lead crystal glass
or polycarbonate? Explain your answer.

Self Reflection

273

CHAPTER 8Manufactured Substances in Industry

3. Traditional ceramics are made from clay such as kaolin.
(a) Name two oxide compounds found in kaolin.
(b) Give the formula of the ion that produces the brown colour in clay.
(c) State two uses of traditional ceramics.

4. The various unique properties of ceramics are modified in its use in various fields. State the
property of ceramic involved in the manufacture of the following objects:

(a) Car engine

(b) Spark plug

5. Metals can conduct electricity. Ceramic materials can also be processed to conduct electricity
and be made superconductors. Figure 1 shows the change in the electrical resistance value
against temperature of two conductors:

0 K 4 K

Non-metal
superconductors

Superconductor X

Temperature

R
es

is
ta

nc
e

Figure 1
(a) Give an example of a ceramic that shows superconductivity properties.
(b) Explain the difference in the electrical conductivity properties of the two conductors
 in Figure 1.

(c) How do scientists create a very cold condition to investigate the superconductivity
phenomena?

CornerEnrichmen

1. Silicon carbide, SiC is a hard and strong substance that melts
at 2700 °C. Silicon carbide, SiC is suitable to be used as an
abrasive. Explain why this substance is hard and has a high
melting point.

Check   AnswersAnswers

https://bit.ly/
2VV6Qct

Figure 1

Carbon, C

Silicon, Si

274

THEME 4 Industrial Chemistry

Components at the end of each chapter:

CHAPTER 2Matter and Atomic Structure

Yourself
TestTest

2.4

Table 2.6

Element Proton
number

Nucleon
number

W 6 12
X 6 13
Y 11 23
Z 12 24

Concept

exists as

phases

differ from the aspects of

can form

consists of

represented
as

Ion

Molecule

Isotopes

Neutron

Proton

Uses

Electron arrangement

Proton
number

Nucleon
number

Atom

Electron

Solid

Arrangement
of particles

Liquid

Kinetic
energy

Gas

Attraction forces
between particles

AXZQuickQuick

http://bit.ly/
2N7Sa5R

1. Define isotopes.

2.  Based on Table 2.6, which atoms are isotopes?
Explain your answer.

3.  Atoms of oxygen-16, oxygen-17 and oxygen-18 are
isotopes. Compare and contrast these three isotopes.

4.  Magnesium exists naturally as three isotopes, which are
79.0% of 24Mg, 10.0% of 25Mg and 11.0% of 26Mg.
Calculate the relative atomic mass of magnesium.

5. Madam Maimunah was diagnosed with bone cancer.
  (a) What isotope is used to treat Madam Maimunah?
  (b) Explain the positive and negative effects of using the isotope in (a).

Matter

39

Self-reflection
Reflection to evaluate students’ learning on the chapter.
Students can download Self-reflection by scanning the
given QR code.

Chain Concept
Brief summary at the end of
each chapter in the form of a
concept map.

Quick Quiz
Scan the QR code to take
the interactive quiz at the
end of each chapter.

Check Answers
Scan the QR code
to get the complete
answer on that chapter.

Enrichment Corner
Enrichment exercises with
HOTS questions at the
evaluation and creation level.

Activities in this book:

Stations

Experiment

Role-play

Discussion

Problem
solving

Simulation

Project

Technology
usage

Laboratory activities Activity

Achievement Test
Questions to test students’
understanding at the end
of each chapter. HOTS
questions at the application,
analysis, evaluation and
creation level are marked
with the HOTS icon .

vi
e-Portal
Provides the link to the
website or the QR code
to get additional information.

Learning or problem
solving tips.

Ti spLiteracy
ChemistryChemistry

Gives extra information
regarding the topic.

Gives information about
careers related to the
chemistry field.

Career Kiosk

Gives information about
patriotic elements, cultural
or Malaysians’ achievements.

Steps that need to be taken
to ensure the results of the
experiment or lab activity
are accurate.

Safety Precaution
A reminder to students
about the dangers while
carrying out the experiment
or laboratory activity.

Cross-curriculum element
Gives cross-curriculum information related to the topic.

Guide to Scan AR (Augmented Reality) for Interactive 3-Dimensional Animation

In this book, there are several pages that contain AR (Augmented Reality) to explain the contents
with interactive three dimensional animation. The pages involved are 25, 29, 113, 115 and 259. The
following guides on how to scan the AR:

Scan the whole page that contains 2

Scan  or  to download the app.1

Icons in this book:

TeaserBrain

TeaserBrain

Questions that hone
students’ thinking skills.

vii

Relates chemical concepts
with our daily life.

Chemistry& Us
Before entering the laboratory
•	 Do	not	enter	the	laboratory	without	the	teacher’s	permission.
•	 Do	not	bring	bags	or	any	food	and	drinks	into	the	laboratory.
While in the laboratory
•	 Do	not	run	or	play	in	the	laboratory.
•	 Do	not	eat	or	drink	in	the	laboratory.
•	 Do	not	taste	or	smell	any	chemical	substances.
•	 Avoid	touching	chemical	substances	with	your	hand.
•	 Do	not	carry	out	any	experiments	without	the	teacher’s	permission.
•	 Understand	all	instructions	before	starting	the	experiment.
•	 Read	all	labels	and	safety	symbols	on	reagent	bottles	before	using	them.
•	 Wear	safety	equipment	such	as	safety	goggles,	gloves	and	laboratory	coats	while	carrying	out	experiments.
•	 Do	not	direct	the	opening	of	the	boiling	tube	to	one’s	self	or	to	others	while	heating	chemical	substances

with a Bunsen burner.
•	 Keep	all	chemical	substances	away	from	the	fire.	Tie	your	hair	and	tidy	your	clothes	so	that	it	does	not

come into contact with fire.
•	 Use	the	required	amount	of	chemical	substances	only.
If there is an emergency
•	 Know	the	location	of	safety	equipment	such	as	a	fire	extinguisher	and	fire	hose	and	ways	to	use	them.
•	 If	a	chemical	substance	comes	into	contact	with	your	eyes,	skin	or	clothing,	wash	immediately	with	plenty

of water.
•	 If	you	accidentally	swallowed	a	chemical	substance,	remove	it	from	your	mouth	and	gargle	with	plenty

of water.
•	 Report	to	the	teacher	as	soon	as	possible	to	get	treatment.
•	 Report	any	accident	or	injury	to	the	teacher	as	soon	as	possible.
Before exiting the laboratory
•	 Switch	off	all	water,	gas	and	electrical	supplies.
•	 Return	all	used	equipments	to	their	original	places.
•	 Clean	and	tidy	up	all	used	equipments.
•	 Throw	all	used	chemical	substances	as	instructed	by	the	teacher.	Do	not	throw	chemical	substances	into

the sink.
•	 Wash	your	hands	before	leaving	the	laboratory.

Laboratory Rules and Safety Measures

Explosive Flammable Oxidant

Corrosive Toxic Health hazard

Irritant

(Source: Department of Occupational Safety and Health (DOSH), Malaysia)

Gas under
pressure

Environmental
hazard

The List of Chemical Symbols

viii
1
THEME

THEME

3

THEME

2

THEME

4

Interaction between
Matter
This theme aims to introduce acids, bases and salts
as well as the rate of reaction.

Fundamentals of
Chemistry
This theme aims to introduce chemistry
from the microscopic aspect which includes
particles, the mole concept, chemical
formulae and equations. The Periodic Table
of Elements and chemical bonds are also
emphasised for a better understanding of
the fundamentals of chemistry.

Industrial Chemistry
This theme introduces properties of materials
that are widely used in the development and
growth of current technology.

The Importance
of Chemistry
This theme introduces students to the meaning of
chemistry, importance of chemistry and careers in the
chemical field as well as chemicals in daily life. Besides,
the application of scientific skills and problem-solving
methods in chemistry are also strengthened from
chemical perspective.

1
What will you learn?
1.1 Development in Chemistry Field and

Its Importance in Daily Life
1.2  Scientific Investigation in Chemistry
1.3   Usage, Management and Handling
 of Apparatus and Materials

Introduction
to Chemistry1

CHAPTER

Chemistry
 Chemical technology
 Scientific method
  Personal protective

equipment
  Safety in the

laboratory
  Management of

laboratory accidents

KeywordsKeywords

2
What is the meaning of chemistry?

What are the careers that require
the knowledge of chemistry?

What are the correct methods to store
chemicals in the laboratory?

Chemistry helps us to understand matter and the reactions
that they go through. Lately, the field of chemistry,
especially nanochemistry has been developing rapidly.
Nanochemistry focuses on the learning and knowledge
of synthesis and properties of particles in nanoscale (as
tiny as 10–9 m). In this field, chemists study the properties
and uniqueness of the atoms and molecules in nanoscale.
Nanochemistry combines nanotechnology, biotechnology,
chemistry, biology, physic and mathematic into one single
field. The discovery of nanochemistry has benefited
humans tremendously, including in the field of medicine,
health, agriculture, electronics, sources and energy,
manufacturing industry and others.
  Knowledge in chemistry is the basis for mastering
nanochemistry. All applications in the world of
nanochemistry begin with the knowledge of chemistry
learned at school. Therefore, mastering the fundamental
concepts of chemistry in secondary school is the beginning
of the expansion of knowledge related to chemistry.

Bulletin

3
LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
1.1.1  State the meaning

of chemistry
1.1.2  State examples of

chemicals commonly
used in daily life

1.1.3  Generate ideas on
the development of
chemistry field and
the contributions of
chemical technology
towards mankind

1.1.4  State examples of
careers related
to chemistry field

Development in Chemistry Field and
Its Importance in Daily Life

1.1

Wow, the fireworks
look beautiful! How
does it produce so
many attractive
colours?

Figure 1.1 Fireworks and chemistry

Meaning of Chemistry

Chemistry is a field of science that studies the structures, properties,
compositions and interactions between matters. Learning of chemistry
is not limited to chemicals found in the laboratory but also substances
commonly found in daily life such as salt and soap. Chemistry helps us
to understand matter around us. The word chemistry originated from
the Arabic word ‘al-kimiya’. Carry out Activity 1.2 to study the origin
of the word chemistry and its meaning.

Activity 1.1
Discussing the meaning of chemistry based on students’ understanding

1. Carry out the Round Table activity.
 2.  Take turns to state the meaning of chemistry according to your understanding on a piece of

blank paper based on:
  (a) The science knowledge that you have learned from Form 1 to Form 3
  (b) Your experience outside the classroom
 3. Present your group findings to your classmates.

Based on Figure 1.1, what do you understand about chemistry?

Fireworks look attractive
especially at night. The
attractive colours are caused
by the mixture of chemicals
in the fireworks. What is

chemistry?

Father of Arabic
chemistry

http://bit.
ly/2qruQIF

Century
Skills21st

4

THEME 1 The Importance of Chemistry
Chemicals in daily life

Chemicals in Daily Life

All substances around us are made up of chemicals. The activities
that we carry out daily involve chemical reactions as well. Figure 1.2
shows the chemicals commonly used in foods, medicine, agriculture
and industries.

Drugs contain
chemicals

http://bit.
ly/2Mx4M7B

Activity 1.2
Collecting and interpreting the origin of the word chemistry and

its meaning

1. Carry out the Think-Pair-Share activity.
 2.  Surf the Internet or refer to reading materials from various printed media to gather information

and discuss the following issues:
  (a) Origin of the word chemistry
  (b) Meaning of chemistry
 3. Present your group discussion results in multimedia form in front of your class.

Figure 1.2 Commonly used chemicals

Food

• Preservative
•	 Colouring
•	 Flavouring
•	 Antioxidant
•	 Stabiliser

Agriculture

•	 Herbicide
•	 Pesticide
•	 Fungicide
•	 Fertiliser
•	 Hormone

Industry

•	 Paint
•	 Polymer
•	 Glass
•	 Ceramic
•	 Detergent
•	 Colouring
•	 Alloy

Medicine

•	 Antibiotic
•	 Antiseptic
•	 Vitamin
•	 Chemotheraphy
•	 Analgesic

Herbicide

Century
Skills21st

5

CHAPTER 1Introduction to Chemistry
The Development in Chemistry Field and the Contributions of

Chemical Technology

Researches in various chemical fields are constantly being carried out covering various disciplines.
For	 examples,	 biochemistry,	 botany	 and	 forensics	 which	 require	 chemical	 knowledge	 to	 solve
problems. The need for chemical technology to solve problems spurs the development of chemical
technology. Technologies used in the 60s and 70s might not be suitable to be applied in this era.
Based on your knowledge, what are the contributions of chemical technology to mankind? Carry
out Activity 1.3.

Figure 1.3 Development of technology in food preservation

Activity 1.3
Searching for information and making a poster

1. Carry out the Gallery Walk activity.
 2. Gather information on the following aspects:
  (a) Contribution of chemists
  (b) Development of chemical technology
  (c) Careers in the field of chemistry
  (d) Chemicals in daily life
 3. Prepare the results of your group in an attractive poster.
 4.  Display your group’s results in the class.
 5.  Each group has to move around to look at the other groups’ posters. Write your comments

about the results of the other groups on sticky notes and paste them on the posters.

Bread with
nanocapsules

Food preservation with
salt or sugar

Food preservation
by freezing

Food preservation
using nanotechnology

Century
Skills21st

Food preservation
using nanotechnology

http://bit.ly/2OKV8jj

6

THEME 1 The Importance of Chemistry
Careers Related to Chemistry

In	the	era	of	rapid	industrial	development,	most	careers	require	knowledge	in	chemistry.
For	example,	careers	in	the	cosmetics,	pharmaceutical,	biotechnology,	nanotechnology	and
green technology fields are shown in Figure 1.4.

Figure 1.4 Several careers related to chemistry

Activity 1.4
Role-playing activity on careers in the field of chemistry

1. Carry out the Role-Play activity.
 2.  Gather information from suitable reading resources or websites on careers in the field of chemistry.
 3. Assign the members of the groups to various careers.
 4. Prepare the acting script and suitable props.
 5. Present your group’s act in front of your class.

CT

Green technology

N
anotechnology

Biotec
hnology Pharmaceutical

Co
sm

et
ic

s

FIELDS

Examples	of
careers:
• Doctor
• Pharmacist

Examples	of
careers:
• Cosmetic

chemist
• Cosmetic

consultant

Examples	of	careers:
• Green	technology	chemist
• Engineer

Examples	of
careers:
• Nanotechnology

engineer
• Food scientist

Examples	of
careers:
• Biotechnology

researcher
• Biomedical

engineer

Century
Skills21st

7

CHAPTER 1Introduction to Chemistry
Yourself
TestTest

1.1

1. What is meant by chemistry?

2. List out five types of chemicals used in daily life.

3.	 Give	one	example	of	development	of	chemistry	in	industries.

4. List out at least three careers related to chemistry in the following situations:
	 	 (a)	 Searching	for	an	antidote	for	dengue	fever
  (b) Producing palm trees with a high content of oil

Figure 1.5 The solubility of salt in hot water

Scientific Investigation in
Chemistry

1.2

Mom, I have been stirring this
salt for a long time. Why is there
still salt in the solution?

Why isn’t the
salt dissolving?

Try to recall the steps in a scientific method that
you have learned in Form 1.

Boys, try adding
some hot water into
the salt solution.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
1.2.1   Design an experiment to

test a hypothesis
1.2.2   Investigate through

experiment the effect
of temperature on the
solubility of salt in water
using a scientific method

A scientific investigation is a scientific method used in solving
problems	 in	 science.	 Generally,	 a	 scientific	 investigation	 begins
with the observation of a problem. Look at Figure 1.5 and identify
the problem that occurs. We can carry out an investigation to solve
the problem by using a scientific method.

8

THEME 1 The Importance of Chemistry
Scientific Method

Scientific	method	is	a	systematic	method	used	by	scientists	or	researchers	to	solve	problems	related
to science. This method involves several general steps to solve a problem using the correct methods.

Figure 1.6 Steps in a scientific method

Making
observations

Using senses of sight, hearing, touch,  taste or smell to gather information about
an object or a phenomenon taking place.

Identifying
the problem Asking	questions	based	on	the	inference	made.

Making an
inference

Using	data	collection	and	past	experience	to	make	a	conclusion	and
explanation	about	an	event.

Making a
hypothesis

Making a general statement about the relationship between a manipulated
variable	and	a	responding	variable	to	explain	an	event	or	observation.	This
statement can be tested to prove its validity.

Identifying the
variables

Identifying	the	manipulated	variable,	responding	variable	and	fixed
variable(s)	in	an	experiment	to	test	the	hypothesis	that	is	formed.

Controlling the
variables

In an investigation, a variable is manipulated to observe its relationship with
the	responding	variable.	Simultaneously,	other	variables	are	fixed.

Planning an
experiment

Determining	the	materials	and	apparatus	to	be	used,	procedure	of	the
experiment,	method	of	collecting	data	and	the	ways	to	analyse	and	interpret
the data.

Collecting
data Making observations or measurements and recording the data systematically.

Interpreting
data

Organising	and	interpreting	the	data	collected.	Data	can	be	interpreted
through calculations, graphs or charts to find and determine the relationship
between the variables.

Making a
conclusion

Making	a	statement	on	the	results	of	the	experiment	on	whether	the
hypothesis made is accepted or rejected.

Preparing a
report

Communicating	in	detail	on	all	aspects	of	the	experiment	so	that	the
outcome	of	the	experiment	can	be	shared	for	the	development	of
chemistry knowledge.

9

CHAPTER 1Introduction to Chemistry
Based	on	the	scientific	method	that	you	have	learned,	carry	out	Experiment	1.1	to	study	the
effect of temperature on the solubility of salt in water.

Experiment 1.1

Prepare a complete report after carrying out this experiment.

Aim: To study the effect of temperature on the solubility of salt in water.

Problem statement:  Does the temperature of water affect the solubility of salt in water?

Hypothesis: The increase in temperature of water will increase the solubility of salt in water.

Variables:

(a) Manipulated : Temperature of water
(b) Responding : Solubility of salt in water
(c) Fixed : Volume of water, mass of salt, time

Materials: Distilled water and salt

Apparatus:  150 cm3 beaker, 100 cm3 measuring cylinder, thermometer, electronic scale, glass rod,
Bunsen burner, stopwatch, wire gauze and tripod stand

Procedure:

1.  Measure 50 cm3 of distilled water at temperature 10 °C
with a measuring cylinder and pour it into a beaker.

2.  Add 40 g of salt into the beaker and stir the solution
with a glass rod for 2 minutes.

3. Observe the solubility of salt in the beaker.
 4.  Repeat steps 1 to 3 with distilled water heated at

30 °C and 80 °C.
 5. Record your observations in Table 1.1.

Results:

Table 1.1

Temperature (oC) 10 30 80

Observation

Interpreting data:

At which temperature does all the salt dissolve in water?

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Glass rod

–1
0

0
10

20
30

40
50

60
70

80
90

10
0

11
0

Salt

Thermometer

Distilled water

Bunsen burner

Figure 1.7

TeaserBrain

TeaserBrain

How can you obtain
distilled water at 10 °C?

10

THEME 1 The Importance of Chemistry
Figure 1.8 A poster of general rules in the laboratory

(Source:	National	Institute	of	Occupational	Safety	and	Health	(NIOSH),	Malaysia)

Yourself
TestTest

1.2

1. What is meant by scientific method?

2.	 Why	is	a	scientific	method	important	in	chemistry?	State	your	opinion.

3.  You are given a bucket of ice cubes, a little sugar, a measuring cylinder and a stopwatch.
Plan	an	experiment	to	determine	whether	sugar	increases	the	melting	rate	of	the	ice.

Usage, Management and
Handling of Apparatus and
Materials

1.3

ChemistryChemistry

CSDS (Chemical Safety
Data Sheet) is a data sheet
that gives information
about chemicals to assist
consumers in managing the
risks of using dangerous
chemicals. This data
sheet contains complete
information on chemical
poisoning besides providing
information on management
and storage methods, and
handling methods during
an emergency.

The laboratory is an important place for learning chemistry, and
it is a dangerous place too. All the rules and safety measures in the
laboratory	should	be	obeyed.	Do	you	still	remember	the	rules	and
safety measures you have learned in Form 1? Figure 1.8 shows a
poster of general rules in the laboratory.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
1.3.1  Explain the types

and functions of self
protective equipments
and safety in the
laboratory

1.3.2  Demonstrate methods of
managing and handling

apparatus and materials
1.3.3  Communicate about

emergency management
procedure in laboratory

11

CHAPTER 1Introduction to Chemistry
Figure 1.9 Personal protective equipment in the laboratory and their functions

Used for preventing dust or splashes of
chemicals from getting into the eyes.

Safety goggles

Used as protection for the body and
clothing against chemical spills such as
acids, alkalis and organic solvents.

Laboratory coat

Used for handling chemicals to
protect hands from injuries, chemicals
or infections.

Gloves

Used for protecting the respiratory
organs from chemicals in the form of
powder or fumes.

Face mask

Used for protecting the feet from
injuries caused by chemical spills, sharp
objects	or	toxic	substances.

Laboratory shoes

Personal Protective Equipment

Wearing	 personal	 protective	 equipment	 while	 carrying	 out	 experiments	 in	 the	 laboratory	 is
necessary	 to	protect	yourself	 from	accidents.	Figure	1.9	 shows	personal	protective	equipment	 in
the	 laboratory	and	their	 functions.	Other	 than	the	personal	protective	equipment,	 the	chemistry
laboratory	is	also	equipped	with	various	safety	equipment.	Figure	1.10	shows	the	safety	equipment
in the laboratory and their functions.

12

THEME 1 The Importance of Chemistry
Used	for	extinguishing	fire	in
the laboratory.

Fire extinguisher

Used for washing and cleaning
the eye when accidents occur
on parts of the eye.

Eyewash

ChemistryChemistry

Examples of substances that release toxic vapour, cause combustion or produce pungent smell:
• Concentrated sulphuric acid   • Chlorine gas   • Ammonia gas   • Bromine gas   • Alcohol   • Benzene

Figure 1.10 Safety equipment in the laboratory and their functions

Used for removing chemical
substances, oil, dirt and
microorganisms from the hands.

Hand wash

A	specially	designed	equipment	to
carry	out	experiments	that	release
toxic	vapours,	cause	combustions	or
produce pungent smells.

Fume chamber

Is used to wash and clean the
body when a chemical accident
occurs on parts of the body.
This	equipment	is	also	used	to
extinguish	fire	on	clothings.

Safety shower

13

CHAPTER 1Introduction to Chemistry
Using and handling apparatus correctly

1. Carry out this activity in groups.
 2.  Each group should take turns in carrying out the four activities according to the stations by using

and handling apparatus and chemicals with the correct methods. Visit the website or scan the QR
code for each station.

(a) Station 1 - Weighing and heating of solid (c)  Station 3 - Electrolysis, gas collection and
   gas test

(b) Station 2 - Filtration and distillation (d) Station 4 - Titration

Methods of Managing and Handling Apparatus and Chemicals

Skills	in	using	and	handling	apparatus	and	materials	are	important	and	very	useful	in	carrying	out
a scientific investigation. Carry out Activity 1.5 to find out the correct methods of managing and
handling apparatus.

Activity 1.5

Station 1

http://bit.ly/
2MzE6Do

Station 2

http://bit.ly/
2pI0scC

Station 3

http://bit.ly/
2MzEMbU

Station 4

http://bit.ly/
2W3RLpl

What do you understand about the storage and disposal
of chemicals based on the conversation in Figure 1.11?
Most chemicals in the laboratory are hazardous.
Chemicals should be stored properly so that they do
not endanger the user nor cause accidents. Therefore,
chemicals should be stored in their designated places
according to their categories.
	 	 Disposal	of	chemicals	is	equally	important	as	the
storage	of	chemicals.	Disposal	of	chemicals	without
following the correct disposal procedures not only
causes environmental pollution but also destroys the
habitats of flora and fauna and endangers human
health	as	well.	Hence,	the	storage	and	disposal	of
chemicals should be taken seriously by all parties.

Figure 1.11 Storage and disposal
 of chemicals

How can the
chemicals in the
laboratory be stored
or disposed of?

Storage and Disposal of Chemicals

Different types of
chemicals should
be stored and
disposed of using
different methods.

14

THEME 1 The Importance of Chemistry
Storage of Chemicals

Chemicals have specific storage methods according to the types of substances.
Look	at	the	following	examples:

Reactive substances

Reactive metals such as lithium, sodium and potassium are stored
in paraffin oil to prevent reaction with the moisture in the air.

Hydrocarbons and organic solvents

Volatile	and	inflammable	liquids	like	hydrocarbons	and	organic
solvents should be stored in shady areas far from sunlight and
heat source.

Substances that decompose easily

Substances	 that	decompose	easily	 in	 the	presence	of	 light,	 for
example	concentrated	nitric	acid,	hydrogen	peroxide	solution,
silver	nitrate	 solution,	 liquid	bromine	 and	 liquid	 chlorine	 are
stored in dark bottles.

Substances with pH<5 and pH>9

Corrosive	chemicals	(pH<5	and	pH>9)	are	usually
stored in special storage cabinets that are
kept locked.

Heavy metals and toxic substances

Toxic	substances	and	heavy	metals	should	be	kept
in special labelled containers and kept in a locked
room which is heat free.

Photograph 1.2 Hydrogen peroxide
 stored in a dark bottle

Photograph 1.1 Sodium in paraffin oil

Photograph 1.3 Cabinet for keeping
 corrosive chemicals

Guidelines on storage of
hazardous substances

http://bit.ly/2MfxBoT

15

CHAPTER 1Introduction to Chemistry
Disposal of Chemicals

Laboratory wastes have specific disposal methods
according to the types of substances.

Hydrogen peroxide
Hydrogen	peroxide	wastes	with	a	 low	concentration	can	be	poured	directly	 into	the	 laboratory’s
sink.	 However,	 hydrogen	 peroxide	 with	 a	 high	 concentration	 has	 to	 be	 diluted	 with	 water	 and
added with sodium sulphite for the decomposition process to take place before being poured into
the sink.

Solid wastes

Solid	wastes	like	glass	and	rubber	have	to	be	disposed	into
special containers.

Organic solvents and hydrocarbons
Most	organic	solvents	and	hydrocarbons	are	toxic,	carcinogenic,
volatile and inflammable. This type of wastes cannot be disposed
directly into the sink or the laboratory drain because it would
pollute the water source and the environment. Organic solvent
and hydrocarbon wastes should be kept in special containers
made of glass or plastic.

Substances with pH<5 and pH>9
Substances	with	a	pH	value	of	pH<5	and	pH>9	are	strong	acids
and	strong	alkalis	respectively.	Strong	acid	and	alkali	wastes	can
cause damage to the sink and react with water to release high
heat	 and	 toxic	 gases.	 Strong	 acid	 and	 alkali	 wastes	 should	 be
kept in closed labelled containers during disposal.

Heavy metals and toxic substances
Solutions	containing	heavy	metals	and	toxic	substances	have	to
be kept in plastic bags and the solutions be left to evaporate in
the fume chamber. Then, the bag of heavy metal residue is tied
carefully and is put into the container of heavy metal waste. This
type of substances should be discarded and disposed according
to standard procedures.

Volatile substances
Substances	 such	as	alcohol,	ammonia	and	bromine	are	volatile,	 that	 is	easily	converted	 to	gas	at
room	temperature.	Some	of	the	gases	produced	from	volatile	substances	are	hazardous	to	humans
and	can	be	fatal	if	inhaled	in	large	amounts.	Volatile	wastes	should	be	stored	in	closed	containers
and kept away from sun and heat.

TeaserBrain

TeaserBrain

Can all the chemical
wastes in the laboratory be
disposed of into the sink or
dustbin? Justify.

Photograph 1.4
A closed container for

disposing hazardous wastes

ChemistryChemistry

According to Malaysian
regulations, chemicals
that are classified as listed
wastes should be disposed
according to standard
procedures. The guidelines
for listed wastes can
be obtained from the
Department of Environment
of Malaysia.

16

THEME 1 The Importance of Chemistry
Emergency Management Procedure in the Laboratory

Waste spills continue to occur in laboratories even with safety measures in place. When these
accidents happen, you should act according to the correct procedure as shown below:

1  Inform your teacher or the laboratory assistant about the accident immediately.

2  Prohibit other students from entering the accident site.

3 	 Stop	the	spill	from	spreading	to	other	areas	by	using	sand	to	border	it.

4  Clean the chemical spill.

5 	 Dispose	of	the	chemical	spill	by	following	the	correct	procedures.

Mercury	thermometers	are	often	used	to	carry	out	experiments
in the school laboratory. If the mercury thermometer breaks, a pupil
faces	 the	 risk	 of	 mercury	 spill.	 Although	 the	 quantity	 of	 mercury
in the thermometer is very minimal, it is enough to cause mercury
poisoning.	Mercury	 poisoning	 occurs	when	 a	 person	 is	 exposed	 to
mercury in certain amount.

Chemical wastes and apparatus
contaminated by chemicals should
be disposed of into bins or bottles
labelled with the types of wastes.
Then, the waste will be sent to
disposal centres.

Photograph 1.5 Bin and bottle for
chemical waste disposal

Figure 1.12 Mercury spill

Mercury is volatile at room
temperature. Mercury vapour
poisons the air.

Do not touch mercury
spill because it can
absorb into your body
through the skin.

News on mercury
spill

http://bit.ly/
2MxQZh9

Symptoms of mercury poisoning:
•	 Nausea
•	 Coughing
•	 Vomiting
•	 Diarrhoea
•	 Chest	pain
•	 Sore	throat
•	 Difficulty	in	breathing
•	 Headache
•	 Eye	irritation
•	 Vision	problem
•	 Increase	in	blood	pressure

17

CHAPTER 1Introduction to Chemistry
Steps	to	be	taken	the	moment	mercury	spill	occurs.

Guidelines on handling
mercury spill

http://bit.ly/
2MJRqng

If you are exposed to mercury poisoning, you should:
 Stay away from the mercury source to prevent
further exposure to it

Go to the hospital for treatment

Yourself
TestTest

1.3

1. List out three safety steps while in the laboratory.

2.	 Give	the	functions	of	the	following	equipment:
  (a) Fume chamber
	 	 (b)	 Safety	shower
  (c) Laboratory coat

3.	 How	would	you	manage	solid	wastes	such	as	glass	and	rubber	in	the	laboratory?

4.	 Explain	how	you	would	test	the	presence	of	oxygen	and	hydrogen	gases.

5.	 Explain	how	you	can	get	the	most	accurate	reading	in	titration.

Discussing the emergency management procedures in the laboratory

1. Carry out the Gallery Walk activity.
 2.  Surf the Internet to gather information on the types of accidents that commonly occur in the

laboratory and emergency management procedures.
 3. Prepare a presentation of your information.
 4. Display the information in the class.
 5.  Each group should move to observe the information of the other groups. Write comments on the

other groups’ information on sticky notes and paste them.

1  Inform your teacher or the laboratory assistant about the accident.

2  Make the spill site as the prohibited area.

3 	 Sprinkle	sulphur	powder	to	cover	up	the	spill.

4 	 Contact	the	Fire	and	Rescue	Department	for	further	action.

Activity 1.6
Century
Skills21st

18

THEME 1 The Importance of Chemistry
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19

CHAPTER 1Introduction to Chemistry
Self Reflection

1. What new knowledge have you learned in Introduction to Chemistry?

2. Which is the most interesting subtopic in Introduction to Chemistry? Why?

3. Why is the learning of Introduction to Chemistry	important	in	the	next	chemistry	lesson?

4.  Rate your performance in Introduction to Chemistry on a scale of 1 to 10; 1 being the
lowest and 10 the highest. Why would you rate yourself at that level?

5.  What else would you like to know about Introduction
to Chemistry?

Achievement 1

1. Chemicals are substances that cannot be ignored in our daily lives.
	 	 (a)	 State	five	types	of	chemicals	that	are	commonly	used	in	daily	life.
  (b) For each chemical stated in (a), state its use.

2. (a) Name three industries in Malaysia that use knowledge of chemistry.
	 	 (b)	How	do	the	industries	stated	in	(a)	benefit	our	country?

3.	 List	out	three	types	of	personal	protective	equipment	and	state	the	function	of	each	equipment.

4. Complete the following flow chart on the steps involved in a scientific method.

Identifying the
problem

Making an
inference

Writing a report

Making
observation

5.	 	State	the	safety	measures	that	should	be	taken	to	overcome	mercury	spill	accidents	that	occur
in the school laboratory.

http://bit.ly/
2MEAuyw

20

THEME 1 The Importance of Chemistry
CornerEnrichmen
 1.	 Figure	1	shows	several	examples	of	waste	substances	in	the	school	laboratory.

Used gloves Used litmus
paper

Broken
conical flask

Bromine

Ethanol Concentrated
acid

Dilute
NaOH

Figure 1

(a)  Based on Figure 1, list out wastes that cannot be disposed of into the school sink or the
rubbish bin.

(b)	Explain	how	to	manage	the	waste	substances	listed	in	(a)	correctly.

2.	 	Halim	is	a	farmer.	He	plants	various	types	of	vegetables	to	supply	the	local	market.	However,
lately,	Halim	realised	 that	 the	produce	was	unsatisfactory	and	the	growth	of	vegetables	was
stunted,	or	the	vegetables	had	died	off.	He	suspected	the	soil	to	be	acidic.	As	a	scientist,	you
are	 asked	 to	 help	Halim	 to	 determine	 the	most	 suitable	 pH	 value	 of	 the	 soil	 for	 planting
vegetables.	Suggest	a	suitable	hypothesis	and	state	briefly	how	you	can	control	the	variables	in
this	experiment.		  STEM

Check   AnswersAnswers

http://bit.ly/
3442zGX

6.  Three pieces of cloth with a size of 10 cm × 10 cm each are sprinkled with 20 cm3 of distilled
water. Then, all the three pieces of cloth are folded in different styles and left to dry at room
temperature. The time taken for each piece to dry is recorded.

(a)	 Explain	why	the	three	pieces	of	cloth	are	folded	in	different	styles.

(b)	 Suggest	a	hypothesis	for	this	experiment.

(c)	 Make	an	inference	for	this	experiment.

(d)	Determine	the	variables	involved	in	this	experiment.

(e)	 Construct	a	suitable	table	to	record	the	readings	in	this	experiment.

21

CHAPTER 1Introduction to Chemistry
What will you learn?
2.1  Basic Concepts of Matter
2.2 The Development of the Atomic Model
2.3 Atomic Structure
2.4 Isotopes and Its Uses

Matter and the
Atomic Structure2

CHAPTER

Atom
 Ion
 Molecule
 Proton number
 Nucleon number
 Electron

arrangement
 Isotopes
 Natural abundance

KeywordsKeywords

22
Who is the scientist that proved the
existence of neutrons in the nucleus?

How many valence electrons are
there in 12

6C?

What is the use of isotope cobalt-60?

Have you heard of patients undergoing PET-CT scanning?
PET-CT is the abbreviation for Positron Emission
Tomography-Computed Tomography. PET-CT scanning can
give accurate information on the position of a disease in
the patient’s body, especially to detect and treat diseases
such as cancer, inflammation and infection. PET-CT is
an imaging technique that combines CT scan and PET
scan. CT is able to visualise the image of a tissue or organ
through the anatomical cross section of organs. PET is able
to show the metabolism level of cells and tissues in the
body of a patient using radioisotopes as a tracer.

Did you know that radioisotopes are isotopes that
exhibit radioactivity? What are isotopes? Do isotopes
have the same subatomic particles like other atoms of
their elements?

Bulletin

23
THEME 2 Fundamentals of Chemistry

Meaning of Matter

Try to recall what matter is based on the conversation in Figure 2.1.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
2.1.1		Describe	matter	briefly
2.1.2  Explain the changes in

the states of matter
2.1.3  Determine the melting

point and freezing
point of naphthalene
through	activity

What are the mass and
volume of a rainbow?

A rainbow does not have
mass nor volume. I agree with Ahmad. A

rainbow is not a matter.

Figure 2.1 Rainbow is not a matter

Matter is something that has mass and occupies space. Matter
consists of particles that are tiny and discrete. Matter can exist in
three states, namely solid, liquid and gas. What are other examples
of matter that you encounter in your daily life?

Changes in the State of Matter

The change in the state of matter is caused by heating or cooling.

Ice cream that is left at room temperature absorbs
heat energy and changes from solid to liquid state.

At night, glass windows release heat to the surroundings
causing the surface of the glass window to become cold.
Water vapour in the air that comes in contact with the cold
surface loses heat and forms water droplets on the surface
of the glass window.

Photograph 2.1 Ice cream

ChemistryChemistry

Plasma is the fourth state
of matter besides solid,
liquid and gas. A plasma
is an ionised gas. Although
plasma in its natural state
is rarely found on Earth,
plasma is the state of
matter most found in the
universe. Most stars exist
as plasma.

Photograph 2.2 Water droplets on the
surface of a glass window

Basic Concepts of Matter2.1

24
CHAPTER 2Matter and the Atomic Structure

Figure 2.2 Conversion between states of matter

Figure 2.2 shows the conversion among states of matter
through the process of heat absorbed or heat released. When
heat energy is absorbed or released, changes occur in kinetic
energy, arrangement of particles and attraction force between
particles, causing the state of matter to change.

Key:
 Heat energy absorbed
 Heat energy released

Solid

Liquid

Gas

Activity 2.1

Solid

FreezingMelting

Sublimation Deposition

Condensation

Liquid

Boiling/
Evaporation

Gas

•	 	Particles	are	closely	packed
in an orderly manner

•	 	Kinetic	energy	of
particles is low

•	 	Attraction	force	between
particles is strong

•	 	Particles	are	closely
packed but not in an
orderly manner

•	 	Kinetic	energy	of	particles
is higher than solid state

•	 	Attraction	force	between
particles is strong, but less
than solid state

•	 	Particles	are	far	apart
•	 	Kinetic	energy	of

particles is very high
•	 	Attraction	force	between

particles is weak

Drawing the arrangement of particles in 2D form

1.  Based on Figure 2.2, draw the arrangement of particles in solid, liquid and gas in 2D form.
 2. Display your work on the notice board in your class.

The difference between
deposition and
sublimation process

http://bit.ly/2IJ8b0X

25
THEME 2 Fundamentals of Chemistry

Matter can exist in the form of elements or compounds. Elements consist of particles of
atoms or molecules while compounds are made up of molecules or ions. Figure 2.3 shows the
classification of matter.

Carbon, C Oxygen, O2 Water, H2O Sodium chloride, NaCl

Matter

Element

Atom MoleculeMolecule Ion

Compound

Figure 2.3 Classification of matter

Activity 2.2

Melting Point and Freezing Point

How do scientists determine the melting point
and freezing point of a substance? Carry out
Activity 2.2 to determine the melting point
and freezing point of naphthalene, C10H8.

•   Melting point is the constant temperature
when a substance changes from solid state
to become liquid at a specific pressure.

•   Freezing point is the constant temperature
when a substance changes from liquid state
to become solid at a specific pressure.

Ti spLiteracy

ChemistryChemistry

Ions are formed by transfer of electrons between atoms.

+

Sodium atom

Donates
1 electron

Sodium ion formed

Na Na

–

Chlorine atom

Accepts
1 electron

Chloride ion formed

Cl Cl

Aim: To determine the melting point and freezing point of naphthalene, C10H8.
Materials: Naphthalene, C10H8 and water
Apparatus:  Boiling tube, 250 cm3 beaker, thermometer, tripod stand, retort stand with clamp,

Bunsen burner, stopwatch, conical flask, wire gauze and spatula

Procedure:

1. Fill up one third of a boiling tube with naphthalene, C10H8.
 2. Place a thermometer in the boiling tube.
 3. Pour water into a beaker until it is half filled.
 4.  Immerse the boiling tube into the beaker as shown in Figure 2.4.

Ensure the level of naphthalene, C10H8 in the boiling tube is
below the level of water in the beaker.

Avoid touching the
naphthalene, C10H8 or inhaling
the naphthalene gas.

26
CHAPTER 2Matter and the Atomic Structure

Prepare a complete report after carrying out this activity.

Thermometer

Boiling tube

Water
Naphthalene, C10H8

–1
0

0
10

20
30

40
50

60
70

80
90

10
0

11
0

Thermometer

Boiling tube

Conical flask
Naphthalene, C10H8

–1
0

0
10

20
30

40
50

60
70

80
90

10
0

11
0

Figure 2.4 10H8 Heating of naphthalene, Figure 2.5 10H8 Cooling of naphthalene,

5.  Heat water and stir the naphthalene, C10H8 slowly using the thermometer. When the
temperature of the napthalene, C10H8 reaches 60 °C, start the stopwatch.

6.  Record the temperature and state of matter of naphthalene,
C10H8 at 30 seconds intervals until the temperature reaches 90 °C.

7.  Remove the boiling tube from the water bath. Dry the outer
surface of the boiling tube and put it into a conical flask as
shown in Figure 2.5.

8.  Stir the naphthalene, C10H8 continuously.
 9.  Record the temperature and state of matter of naphthalene, C10H8

at 30 seconds intervals until the temperature decreases to 60 °C.
 10.  Record your observations.

Interpreting data:

1. Plot a graph of temperature against time for the following:
  (a) Heating of naphthalene, C10H8
  (b) Cooling of naphthalene, C10H8

2.  On the graphs, label the states of matter of naphthalene, C10H8 whether solid, liquid or both.
 3.  Determine the melting point and freezing point of naphthalene, C10H8 from the graphs plotted.

Discussion:

1. During the heating of naphthalene, C10H8:
  (a) Why is naphthalene, C10H8 not heated directly using the Bunsen burner?
  (b) Why is a water bath used?
 2. During the cooling of naphthalene, C10H8:
  (a) Why is the boiling tube put into a conical flask?
  (b) Why is naphthalene, C10H8 stirred continuously?
  (c) Predict what would happen if naphthalene, C10H8 is not stirred continuously.
 3.  Explain why the temperature becomes constant when melting and freezing of naphthalene,

C10H8 take place.

Deficiency of glucose-6-
phosphate dehydrogenase
(G6PD) is a genetic disease.
Exposure to naphthalene,
C10H8 to a patient with G6PD
will cause haemolysis, that
is destruction of red blood
cells. This situation will
cause the patient to feel tired
and dizzy.

27
THEME 2 Fundamentals of Chemistry

The graph of temperature against time for heating of
naphthalene, C10H8 is shown in Figure 2.6 and the graph of
temperature against time for cooling of naphthalene, C10H8 is
shown in Figure 2.7.

E

F G

H

Temperature (°C)

Freezing
point

Time (min)

A

B C

D
Temperature (°C)

Melting
point

Time (min)

Figure 2.6 Heating curve of naphthalene, C10H8

Figure 2.7 Cooling curve of naphthalene, C10H8

ChemistryChemistry

Lauric acid, C12H24O2 is a
type of fatty acid that can
be obtained from coconuts.
This acid is also suitable to
be used as a substitute for
naphthalene, C10H8 in
Activity 2.2.

•	 Temperature	increases	from	C to D
•	 Exists	in	liquid	state
•	 	When	 heated,	 the	 particles	 absorb	 heat

and move faster

•	 Temperature	increases	from	A to B
•	 Exists	in	solid	state
•	 	When	heated,	the	particles	absorb	heat	energy	and	vibrate	faster
because	kinetic	energy	increases

•	 Melting	occurs
•	 	No	increase	in	temperature	from	B to

C because	heat	energy	absorbed	by
the particles is used to overcome the
attraction force between the particles
until	solid	changes	to	liquid

•	 Temperature	decreases	from	G to H
•	 Exists	in	solid	state
•	 	When	cooled,	the	particles	release	heat

and vibrate slower

•	 Freezing	occurs
•	 	No	decrease	in	temperature	from	F

to G	because	heat	energy	that	is	lost
to	the	surroundings	is	balanced	by
the	heat	energy	released	when	the
particles attract each other to form
solid

•	 Temperature	decreases	from	E to F
•	 Exists	in	liquid	state
•	 	When	cooled,	the	particles	release

heat and move slower due to the
lost	of	kinetic	energy

28
CHAPTER 2Matter and the Atomic Structure

Subatomic Particles

Figure 2.8 shows the subatomic particles found in an atom which  is
made up of protons, neutrons and electrons. What are the similarities
and differences in these three types of subatomic particles?

Yourself
TestTest

2.1

The Development of
the Atomic Model

2.2

Activity 2.3

Figure 2.8 Subatomic particles

Electron

Symbol: e
Relative charge = –1

Relative mass = 1
1840

Proton

Symbol: p
Relative charge = +1

Relative mass = 1

Neutron

Symbol: n
Relative charge = 0

(Neutral)
Relative mass = 1

TeaserBrain

TeaserBrain

How are the relative
charge and relative mass
of subatomic particles
determined?

1. State the types of particles that exist in a copper wire.
 2. Lily dries her hair with a hair dryer.
  (a) Name the process involved during hair drying.
  (b) State the changes in the movement of water particles when hair is dried.
 3.  Lauric acid, C12H24O2 is heated from room temperature to 50 °C. At 43 °C,

lauric acid, C12H24O2 starts to melt.
  (a) Draw a heating curve for lauric acid, C12H24O2.

(b) Why is the temperature constant at 43 °C?

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
2.2.1  State the subatomic

particles in atoms of
various elements

2.2.2  Compare and contrast the
relative mass and relative
charge of proton, electron
and neutron

2.2.3	 	Sequence	the	atomic
structure models based
on	Atomic	Models
of	Dalton,	Thomson,
Rutherford, Bohr
and Chadwick

Comparing and contrasting the subatomic particles

1.  Watch a video clip on subatomic particles by searching the Internet.
 2.  Based on the video, compare and contrast the relative masses and charges of protons, electrons

and neutrons.
 3.  Present your findings using a suitable graphic presentation software and upload your work to

social media.

29
THEME 2 Fundamentals of Chemistry

Development of the Atomic Structure Model

Atoms can neither be seen with the naked eye nor the microscope. Have you ever thought how the
atomic structure model is produced? The atomic structure model that we know now is the product
of many scientists’ efforts. Studies on atoms started since the introduction of atomic theory by
Democritus, a Greek philosopher, around 500 B.C. Figure 2.9 shows the historical development of
the atomic structure model.

•	 Discovered negatively-charged
particles called electrons

•	 Atom is a positively-charged
sphere with several electrons
in it

•	 Nucleus is the centre of the atom
•	 Discovered positively-charged

particles called protons
in the nucleus

•	 Almost the whole of atomic mass
is concentrated in the nucleus

•	 Electrons move outside
the nucleus

Thomson’s Atomic ModelDalton’s Atomic Model Rutherford’s Atomic Model

Figure 2.9 Historical development of the atomic model

•	 Matter is made up of
particles called atoms

•	 An atom is the smallest
spherical body that cannot
be created, destroyed nor
divided further

•	 Same elements have the
same atoms

Electron

Positively-charged
sphere

–

–
– –

– –
–

Electrons move
outside the nucleus

Nucleus consists
of protons

–

–
– –

– –
–

+

John Dalton
(1766 – 1844)

J.J. Thomson
(1856 – 1940)

Ernest Rutherford
(1871 – 1937)

30
CHAPTER 2Matter and the Atomic Structure

Activity 2.4

•	 Discovered neutral particles, that are
neutrons in the nucleus

•	 Neutrons contribute almost half of the
mass of an atom

Chadwick’s Atomic Model

•	 Electrons in an atom move in shells
around the nucleus

Bohr’s Atomic Model

Shell

Electron

+
Nucleus that
contains
protons

Shell

Electron

Nucleus that
contains protons
and neutrons

James Chadwick
(1891 – 1974)

Niels Bohr
(1885 – 1962)

Role-playing on the development of the atomic structure model

1. Carry out the Role-Play activity in groups.
 2. In your group, find information on the atomic structure model explained by one of the
  following scientists:

John Dalton   Ernest Rutherford   James Chadwick

J.J. Thomson   Niels Bohr

3. Prepare the acting scripts and suitable props.
 4. Present the group act in front of the class.

Century
Skills21st CT

31
THEME 2 Fundamentals of Chemistry

1. Figure 2.10 shows the atomic structure of nitrogen.
  (a) Name X.
  (b)  State the subatomic particles found in the nucleus

of nitrogen atom.
  (c)  Compare X and subatomic particles mentioned in (b)

from the aspect of relative charge and relative mass.
 2. •	Electrons	move	around	the	nucleus	in	shells.

•	Nucleus	of	an	atom	consists	of	protons	and	neutrons.

The statements above show the information on an atomic structure model.
  (a) Which scientist identified it?
  (b) Draw this atomic structure model.

Figure 2.10

Proton Number and Nucleon Number

Look at Table 2.1, what is the relationship between the number
of protons and proton number, and the relationship between the
nucleon number and the proton number?
 Table 2.1 Proton numbers and nucleon numbers of oxygen atom,

sodium atom and chlorine atom

Atom Number of
protons

Number of
neutrons

Proton
number

Nucleon
number

Oxygen 8 8 8 16

Sodium 11 12 11 23

Chlorine 17 18 17 35

The number of protons in the nucleus of an atom is known
as the proton number. The total number of protons and neutrons
in the nucleus of an atom is known as the nucleon number.

Nucleon number = number of protons + number of neutrons
or

Nucleon number = proton number + number of neutrons

Atoms of different elements have different proton numbers.
For example, sodium atom has a proton number of 11 and chlorine
atom has a proton number of 17.

Yourself
TestTest

2.2

Atomic Structure2.3

TeaserBrain

TeaserBrain

Are there any two elements
with the same proton
number? Explain.

X

Nucleus

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
2.3.1	 	Define	proton	number

and nucleon number
2.3.2  Determine the nucleon

number, proton number
and number of electrons
in an atom

2.3.3  Write the standard
representation of an atom

2.3.4  Construct an atomic
structure diagram and
electron arrangement

32
CHAPTER 2Matter and the Atomic Structure

An aluminium atom has 13 protons and 14 neutrons. What are the proton number and nucleon
number of an aluminium atom?
Solution

Proton	number	=	number	of	protons
 = 13
Nucleon number = proton number + number of neutrons
 = 13 + 14
 = 27

Example 1

The nucleon number of a potassium atom is 39. A potassium atom has 19 protons. How many
neutrons and electrons are there in a potassium atom?
Solution

Number of electrons = number of protons
 = 19
Number of neutrons = nucleon number – number of protons
 = 39 – 19
 = 20

Example 2

Table 2.2 shows the comparison among the number of protons, neutrons and electrons when
a chlorine atom accepts an electron to form a chloride ion. What are the changes in the number
of protons, neutrons and electrons?

Table 2.2 Number of subatomic particles of chlorine atom and chloride ion

Type of particle Chlorine atom, Cl Chloride ion, Cl-

Number of proton 17 17

Number of neutron 18 18

Number of electron 17 18

A chlorine atom accepts one electron to form a
chloride ion, thus a chloride ion has one electron more
than a chlorine atom. The number of protons and neutrons
in a chlorine atom and chloride ion are the same. Therefore,
during the formation of ion from an atom, the number of
protons and neutrons in the nucleus remain the same.

An atom is neutral when the number of electrons is the same with the number of protons.
For example, an oxygen atom has 8 protons and also 8 electrons. The examples and solutions are
shown in Example 1 and 2.

When the number of electron
increases, an anion is formed, which
is a negatively-charged ion. However,
when the number of electron
decreases, a cation is formed, which
is a positively-charged ion.

Ti spLiteracy

33
THEME 2 Fundamentals of Chemistry

Standard Representation of an Atom

An atom can be represented using a standard representation as shown in Figure 2.11.

Symbol	of	element

AXZProton number

Nucleon	number

Figure 2.11 Standard representation of an atom

What information can you obtain from 12
C6

? The symbol of carbon element is C,

the nucleon number of a carbon atom is 12, while the proton number of a carbon atom is 6.

Activity 2.5

A sodium atom contains 12 neutrons and
11 protons in the nucleus. What is the
standard representation of a sodium atom?

Code guidance

http://bit.ly/2P8zNQV

CTFinding the mystery code

1. In groups, answer the following questions:
  (a)  The nucleon number and the proton number of fluorine element are 19 and 9 respectively. Is

the following statement true or false?

The atom of this element has 9 electrons and 9 neutrons in its nucleus.

(b) Atom X has 11 protons and 12 neutrons. Find the nucleon number of this atom.
  (c) What is the proton number of an atom of nitrogen element that has 7 electrons?
  (d)  The standard representation of an atom of oxygen element is 16

8O. This atom accepts electrons
to form an oxide ion, O2–. How many electrons are accepted by an oxygen atom to form an
oxide ion, O2–?

(e)  The nucleus of atom Y  has the charge +4 and contains 5 neutrons. State the nucleon number
of element Y.

(f)  A calcium atom has 20 protons and its nucleon number is 40. A calcium ion, Ca2+ is formed
when a calcium atom donates 2 electrons. State the number of neutrons in a calcium ion, Ca2+.

(g) 7
W

An atom of element W has 3 electrons and 4 neutrons. What should the number in
the box be, to represent the atom of element W?

2.  Scan QR Code or visit the website provided to obtain the
code guidance.

3. Get the mystery code.

34
CHAPTER 2Matter and the Atomic Structure

Atomic Structure and Electron Arrangement

Electrons of an atom orbit around the nucleus in their respective shells. Electrons will fill the shell
closest to the nucleus first. When the shell closest to the nucleus is full, electrons will fill the next
shell. The maximum number of electrons in the first three shells for elements with proton numbers
1 to 20 are shown in Figure 2.12.

Figure 2.12 Numbers of maximum electrons in the first three shells for
 elements with proton numbers 1 to 20

For example, the proton number of aluminium is 13. This shows that an aluminium atom
has 13 electrons. The electron arrangement of aluminium atom is, 2 electrons filled in the first
shell, 8 electrons filled in the second shell and 3 electrons filled in the third shell. The electron
arrangement of aluminium atom can be written as follows:

2.8.3 Number	of	valence	electrons	=	3

The outermost shell filled with electrons is the valence shell.
Electrons in the valence shell are known as valence electrons.
The chemical properties of an element depend on the number of
valence electrons of the atom. Elements with the same number of
valence electrons have similar chemical properties.

ChemistryChemistry

The third shell can be filled
with a maximum of 18
electrons for elements
with proton number
exceeding 20.

ChemistryChemistry

The valence shell is the
outermost shell of an atom.

Nucleus First shell: 2 electrons

Second shell: 8 electrons

Third shell: 8 electrons

The electron arrangement shows the
nucleus and electron arrangement of
an atom. For example, the electron
arrangement of aluminium atom is
shown in Figure 2.13.

Figure 2.13 Electron arrangement of aluminium atom

Al

The atomic structure shows the number
of protons and neutrons in the nucleus
and electron arrangement of an atom.
For example, the atomic structure of
aluminium is shown in Figure 2.14.

Figure 2.14 Atomic structure of aluminium atom

13 p
14 n

35
THEME 2 Fundamentals of Chemistry

Yourself
TestTest

2.3

Activity 2.6

Activity 2.7
CT

CT

Illustrating the atomic structure using a model

1. Carry out this activity in groups.
 2.  Choose an element from the elements with proton numbers 1 to 20. Produce a model to

illustrate the atomic structure using recycled materials.
 3. The model that is produced must include the following:
  (a) Protons and neutrons in the nucleus
  (b) Electron arrangement in the shells
 4. Present the model in front of the class.

Writing the electron arrangement and drawing the atomic structure

1.  Get the standard representation of atoms of the first 20 elements
in the Periodic Table of Elements from the QR code or the
given website.

Based on the information:
  (a) Write the electron arrangement of the 20 elements
  (b) Draw the atomic structure of the 20 elements
 2. Display your work on the notice board in your class.

Table 2.3 shows the number of protons and the number of neutrons for elements X, Y and Z.
Table 2.3

Element Number of protons Number of neutrons
X 10 10
Y 11 12
Z 19 20

1. What is the nucleon number of atom Y?

2. Write the standard representation of element Z.

3.  Atom Y donates one electron to form ion Y+. State the number of protons, neutrons and
electrons for ion Y+.

4. (a) Write the electron arrangement of atom X.
  (b) Draw the electron arrangement for atom X.
  (c)  Draw the atomic structure of atom X. Label all the subatomic particles in the diagram.

Standard
representation
of atoms

http://bit.ly/2qusDfC

36
CHAPTER 2Matter and the Atomic Structure

Isotopes are atoms of the same element with the same number
of protons but different number of neutrons. For example, chlorine
has two isotopes, chlorine-35 and chlorine-37. Table 2.4 shows the
number of subatomic particles for the isotopes of chlorine. Atoms
of chlorine-35 and chlorine-37 have different masses because the
number of neutrons in the nucleus are different.

Table 2.4 Number of subatomic particles for the isotopes of chlorine

Isotope Atomic standard
representation Number of protons Number of neutrons Number of electrons

Chlorine-35
35Cl
17 17 18 17

Chlorine-37 37Cl
17

17 20 17

Relative Atomic Mass of Isotopes

Most elements exist naturally as a mixture of two or more isotopes. Relative atomic mass of these
elements depend on the natural abundance of isotopes in a sample. Natural abundance is the
percentage of isotopes present in a natural sample of element. The relative atomic mass can be
calculated from the natural abundance of an element containing isotopes using the following formula:

Relative atomic mass = ∑(% isotope × mass of isotope)
100

Activity 2.8

Meaning of Isotopes

Figure 2.15 shows three atoms of hydrogen
element. All these three atoms of hydrogen
have the same proton number but different
nucleon numbers. These hydrogen atoms
are known as isotopes.

Isotopes and Its Uses2.4

Figure 2.15

1H1 2H13H1

LearningLearning
StandardStandard

At the end of this lesson,
pupils are able to:
2.4.1  Deduce the meaning

of isotopes
2.4.2  Calculate the relative

atomic mass of isotopes
2.4.3	 	Justify	the	usage	of

isotopes	in	various	fields

Generalising the meaning of isotopes

1. Carry out this activity in groups.
 2.  Compare and contrast the number of protons, electrons and neutrons in the isotopes of silicon,

magnesium and phosphorus.
28
Si

14

29
Si

14

30
Si

14

24
Mg

12

25
Mg

12

26
Mg

12

31
P

15

32
P

15

3. Interpret the information obtained and generalise the meaning of isotopes.

ChemistryChemistry

Chlorine atom with the
nucleon number 35 can be
represented by Cl-35,
35

Cl17  or 35Cl.

37
THEME 2 Fundamentals of Chemistry

Uses of Isotopes

Isotopes are used widely in various fields as listed in Table 2.5.
Table 2.5 Uses of isotopes in various fields

Field Isotope Uses

Medicine Cobalt-60 •	 In	radiotherapy	to	kill	cancer	cells	without	surgery
•	 Sterilising	surgical	tools

Iodine-131 •	 Treatment	of	thyroid	disorders	such	as	hyperthyroidism	and	thyroid
cancer

Agriculture Phosphorus-32 •	 Study	of	plant	metabolism

Nuclear Uranium-235 •	 Generating	electricity	through	nuclear	power	generator

Archaeology Carbon-14 •	 Estimation	of	artifacts	or	fossils’	age

Lead-210 •	 In	determining	the	age	of	sand	and	earth	layers	up	to	80	years

Industry Hydrogen-3 •	 As	a	detector	to	study	sewage	and	liquid	wastes

Engineering Sodium-24 •	 In	detecting	leakage	in	underground	pipes

Development in the field of science, specifically chemistry
has maximised the use of isotopes in various fields. Isotopes are
used for sustainability of life. The use of isotopes causes both
positive and negative effects on the environment and society.

Activity 2.9
Holding a forum on the issues of using isotopes

1. Carry out this activity in groups.
 2.  Each group is given a role as a chemist, medical representative, enforcer and others. Based on the

role given, search for information concerning issues involving isotopes.
 3. Hold a forum to discuss the positive and negative effects of using isotopes.
 4. Record the forum proceedings and upload to social media.

Chlorine consists of two isotopes, 35Cl
17  and 37Cl

17 . The natural abundance of 35Cl
17  is 75% and 37Cl

17
is 25%. Calculate the relative atomic mass of chlorine.
Solution

Relative atomic mass of chlorine =
(% isotope 35Cl

17  × mass 35Cl
17 ) + (% isotope 37Cl

17  × mass 37Cl
17 )

100

= (75 × 35) + (25 × 37)
100

= 35.5

Example 3

Century
Skills21st

Uses of isotopes

http://bit.ly/
32zUJUP

38
CHAPTER 2Matter and the Atomic Structure

Yourself
TestTest

2.4

Table 2.6

Element Proton
number

Nucleon
number

W 6 12
X 6 13
Y 11 23
Z 12 24

Concept

exists as

phases

differ from the aspects of

can form

consists of

represented
as

Ion

Molecule

Isotopes

Neutron

Proton

Uses

Electron arrangement

Proton
number

Nucleon
number

Atom

Electron

Solid

Arrangement
of particles

Liquid

Kinetic
energy

Gas

Attraction forces
between particles

AXZQuickQuick

http://bit.ly/
2N7Sa5R

1. Define isotopes.

2.  Based on Table 2.6, which atoms are isotopes?
Explain your answer.

3.  Atoms of oxygen-16, oxygen-17 and oxygen-18 are
isotopes. Compare and contrast these three isotopes.

4.  Magnesium exists naturally as three isotopes, which are
79.0% of 24Mg, 10.0% of 25Mg and 11.0% of 26Mg.
Calculate the relative atomic mass of magnesium.

5. Madam Maimunah was diagnosed with bone cancer.
  (a) What isotope is used to treat Madam Maimunah?
  (b) Explain the positive and negative effects of using the isotope in (a).

Matter

39
THEME 2 Fundamentals of Chemistry

Self Reflection

Achievement 2

1.  Table 1 shows the melting point and boiling point of substances A, B, C, D and E.
Table 1

Substance Melting point (°C) Boiling point (°C)
A –101.0 –35.0
B –94.0 65.0
C 17.8 290.0
D 97.8 883.0
E 801.0 1413.0

(a) Classify substances A, B, C, D and E according to states of matter at room temperature.
  (b)  State the substance that will change from liquid to solid when placed in the freezer at

temperature 2 °C.

(c)  Describe the changes that take place on the particles of substance B with relation to
energy and attraction force between particles when cooled from 80 °C to –2 °C.

2.  A group of students carried out an experiment to
determine the melting point of lauric acid, C12H24O2.
Figure 1 shows the heating curve obtained.

(a)  Copy Figure 1 and label the melting point of
lauric acid, C12H24O2 on the diagram.

(b)  Draw the arrangement of particles in lauric acid,
C12H24O2 between R and S.

(c)  The melting point of lauric acid, C12H24O2 is 43 °C.
Suggest a suitable method of heating lauric
acid, C12H24O2.

(d)  Draw a labelled diagram to show the set-up of
apparatus for the method suggested in (c).

1. What new knowledge have you learned in Matter and Atomic Structure?
 2.  Which is the most interesting subtopic in Matter and Atomic Structure? Why?
 3.  Give a few examples on the application of Matter and Atomic Structure in daily life.
 4.  Rate your performance in Matter and Atomic Structure

on a scale of 1 to 10; 1 being the lowest and 10 the highest.
Why would you rate yourself at that level?

5.  What else would you like to know about Matter and
Atomic Structure?

Figure 1

P

Q R

S

Temperature (°C)

Time (min)

http://bit.ly/
2Mkz7Xa

40
CHAPTER 2Matter and the Atomic Structure

CornerEnrichmen
 1.  You lost your way while camping in a jungle. You felt thirsty

but could not find a water source. In your bag, there were
a transparent plastic bag and a string. Using the available
things, describe how you could produce water through the
condensation process.    STEM

Relative atomic mass of boron = 10.81
80% 11B
20% isotope Boron-Y

Figure 3

195   Pt
  78
Figure 4

3.  Chen Ling cleans her wound using alcohol as shown in
Photograph	1.	Chen	Ling’s	skin	feels	cool	when	wiped
with alcohol. Explain this situation.

4.  Figure 2 shows the nucleus charges of the atoms of
elements X, Y and Z.

+3

+9

+13

X Y Z
Figure 2

(a) State the subatomic particle that provides the charges in the atoms of the elements.
  (b) State the other subatomic particle found in the nucleus of the atoms.
  (c) Write the electron arrangement of the atoms for elements X, Y and Z.
  (d) Atom Z contains 14 neutrons. Calculate the nucleon number of atom Z.

5.  Figure 3 shows the information on boron. Boron
has two isotopes, namely isotope 11B and isotope yB.
Based on the information given, calculate the
nucleon number of isotope yB.

6.  Figure 4 shows the standard representation of a platinum
atom. A platinum ion contains 74 electrons and has a
nucleon number of 195.

(a)  What are the number of protons and neutrons in
the platinum ion?

(b) What is the charge of the platinum ion?

7. Justify the use of iodine-131 in the treatment for hyperthyroidism.

Check   AnswersAnswers

http://bit.ly/
2odL87q

Photograph 1

Cotton
swab

41
The Mole
Concept,
Chemical
Formula and
Equation

What will you learn?
3.1	 Relative	Atomic	Mass	and	Relative	Molecular	Mass
3.2	 Mole	Concept
3.3	 Chemical	Formula
3.4	 Chemical	Equation

3
CHAPTER

Chemical formula
 Molar volume
 Relative atomic

mass
 Relative formula

mass
 Molar mass
  Relative molecular

mass
 Mole
 Chemical equation

KeywordsKeywords

42
How	do	you	write	the	formula	of	a
chemical	substance?

What	information	is	found	in	a
chemical	equation?

How	do	you	measure	the	quantity	of	a
chemical	substance?

Satay is a favourite food among Malaysians. Satay is
made from pieces of spiced meat skewered on coconut or
bamboo skewers and grilled over burning charcoal.
  Did you know that the burning of charcoal is a form
of chemical reaction? This reaction can be represented by
the following chemical equation.

C(s) + O2(g) → CO2(g)

The symbol ‘C’ in the equation shows the chemical
formula of carbon element in the charcoal. What is a
chemical formula? What are the meanings of the other
letters and numbers in the above equation?

Bulletin

43
Relative Atomic Mass and Relative Molecular Mass3.1

Relative Atomic Mass, RAM

Chemists use the concept of  ‘relative atomic mass’ by comparing the
mass of atom of an element to the mass of atom of another element
that is chosen as the standard. Therefore, we do not need to know the
actual mass of an atom.
  Initially, the hydrogen atom was used as the standard atom
because it is the lightest atom. Masses of atoms of all other elements
were compared with the hydrogen atom. For example, one carbon
atom is as heavy as 12 hydrogen atoms. Hence, the relative atomic
mass of carbon is 12 while the relative atomic mass of hydrogen is
assigned as one as shown in Figure 3.1.
  However, in 1961, chemists across the world agreed to use
carbon-12 atom as the standard atom after finding that the usage of
hydrogen atom as the standard atom encountered various problems.
The relative atomic mass, RAM of an element is defined as the
average mass of an atom of the element compared to 1

12 of the mass
of one carbon-12 atom.

Relative atomic
mass of an element  = Average mass of one atom of the element

1
12 × Mass of one carbon-12 atom

Figure 3.1
Mass of carbon atom

compared to hydrogen atom

One carbon
atom

12 hydrogen
atoms

Photograph 3.1 Rice

Have you ever tried counting the number
of rice grains in a sack of rice? Rice grains
cannot be counted because their size is
extremely small. Chemists face a similar
problem too. As atoms are too small, it is
difficult to determine their number and
the mass of each atom. How do chemists
overcome this problem?

TeaserBrain

TeaserBrain

Determining the relative
atomic mass of hydrogen
atom as the standard atom
has encountered various
problems. Try to investigate
what the problems are.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
3.1.1  Conceptualise relative

atomic mass and relative
molecular mass based
on the carbon-12 scale

3.1.2  Calculate relative
molecular mass and
relative formula mass

Explain why there is
a value of 1

12 in the
definition of the relative
atomic mass based on
the carbon-12 scale.

One atom of carbon-12
is given a definite mass
of 12 units.

So, 1
12 of the mass of a

carbon-12 atom is the same
as the mass of one hydrogen
atom, that is 1 unit.

44

THEME 2 Fundamentals of Chemistry
Figure 3.2 Relative atomic mass of helium

TeaserBrain

TeaserBrain

One magnesium atom is
twice as heavy as one atom
of carbon-12. What is the
RAM of magnesium?

18 unitsOne molecule
 of water

Relative Molecular Mass, RMM

Similarly, we can compare the molecular mass of a substance with
the standard carbon-12 atom. The relative molecular mass, RMM
of a molecule is the average mass of the molecule compared to 1

12
of the mass of one carbon-12 atom.

Relative molecular
mass of a substance  = Average mass of one molecule

1
12 × Mass of one carbon-12 atom

Figure 3.3 shows water molecule that has a relative molecular mass of 18. This means the mass
of a water molecule is 18 times the mass of 1

12 of carbon-12 atom. Activity 3.2 can strengthen your
understanding on the concepts of relative atomic mass and relative molecular mass based on the
carbon-12 scale as an analogy.

Activity 3.1

The relative atomic masses
of elements are given in the
Data Table of Elements on
page 276. Since the relative
atomic mass is a comparative
value, it has no unit.

Ti spLiteracy
One helium atom 4 units

Discussing why carbon-12 is used as the standard to determine RAM

1.  Carry out the activity in groups.
 2.  Gather information from printed reference materials or surf the Internet and discuss why

carbon-12 is used as the standard to determine the relative atomic mass.
 3. Present your group discussion results in a suitable thinking map.

Carbon-12 is chosen as the standard because it is a solid at room temperature and thus can
be handled easily. Carbon-12 combines easily with other elements. Therefore, this element is found
in most substances. Although carbon has three isotopes, carbon-12 is the major isotope with the
abundance of 99%. This makes the relative atomic mass of carbon-12 exactly 12.0.

The relative atomic mass of
helium is 4. This means the
average mass of one atom of
helium is 4 times the mass of
1
12 of carbon-12 atom.

Figure 3.3 Relative molecular
 mass of water

45

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Activity 3.2
Studying the concepts of relative atomic mass and relative molecular mass by analogy

Materials:  36 washers, one 5 cm bolt, five nuts, one flat magnet and strings
Apparatus: Two-pan balance

Relative atomic mass based on the carbon-12 scale

Procedure:
 1.  You are given three models of carbon-12 atom.

Calculate the number of washers required to form
each model of carbon-12 atom.

2.  Separate the washers in each model and use them for
the following steps.

3.  Place an atom of element A on a two-pan balance as
shown in Figure 3.4.

4.  Place the washers on the other pan one by one until
they are balanced.

5.  Count and record the number of washers used
in Table 3.1.

6.   Repeat steps 3 to 5 using atom of element B and
atom of element C.

7.  Calculate the relative mass of each washer in the
model by assuming that each atom of carbon-12 is
given the accurate mass of 12 units. Then, deduce
the relative atomic masses of elements A, B and C.

Results:

Table 3.1

Atom of element Number of washers used Relative atomic mass
A
B
C

Discussion:

1. How many washers form a model of carbon-12 atom?
 2. What is represented by 1

12 of the mass of carbon-12 atom in this activity?
 3. Define the relative atomic mass of an element based on the carbon-12 scale.

Relative molecular mass based on the carbon-12 scale

Procedure:

1.  Prepare models of molecules X, Y and Z as
in Photograph 3.3.

2.  Place molecule X on one of the pans of
the balance.

3.  Place washers on the other pan one by one
until they are balanced.

Washers

Model of carbon-12 atom Atom of element A

Atom of element C

Photograph 3.2
A model of carbon-12 atom and

three elements A, B and C

Atom of
element A

Washers

Pan

Figure 3.4  Studying the relative
mass by analogy

Atom A

Atom B
Molecule X

Atom A

Atom B
Molecule Y

Atom A

Atom C

Molecule Z
Photograph 3.3 Models of molecules X, Y and Z

Atom of element B

46

THEME 2 Fundamentals of Chemistry
4. Count and record the number of washers used in Table 3.2.
 5. Repeat steps 2 to 4 using molecule Y and Z.
 6. Deduce the relative molecular masses of X, Y and Z.

Results:

Table 3.2

Molecule   Composition of molecule Number of washers used Relative molecular mass
X 1 atom A + 1 atom B
Y
Z

Discussion:

1. Based on Activity B, give the definition of relative molecular mass based on the carbon-12 scale.
 2. Calculate the relative atomic masses of all the elements that form molecules X, Y and Z.
 3.  Compare the answers from question 2 with the relative molecular masses you obtained in

Activity B. What inference can you make about the relationship between the relative molecular
mass and the relative atomic mass?

4.  Molecule W is formed from one atom of element A, one atom of element B and one atom of
element C. Predict the relative molecular mass of W.

Figure 3.5 Calculation of the relative molecular mass, RMM

Calculate the relative molecular mass of glucose, C6H12O6.
[Relative atomic mass: H = 1, C = 12, O = 16]

Solution

RMM of glucose, C6H12O6 = 6(RAM of C) + 12(RAM of H) + 6(RAM of O)
 = 6(12) + 12(1) + 6(16)
 = 72 + 12 + 96
 = 180

Example 1

Prepare a complete report after carrying out this activity.

Relative molecular mass
of a molecule is similar to
the total of relative atomic
mass of all atoms in the
molecule.

Ti spLiteracy
  The relative molecular mass of a molecule can be calculated
by adding up the relative atomic masses of all the atoms that
form the molecule, as shown in Figure 3.5 and Example 1.

RMM of oxygen gas, O2
= 2(RAM of O)
= 2(16)
= 32

RMM of water, H2O
= 2(RAM of H) + RAM of O
= 2(1) + 16
= 18

47

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Relative Formula Mass, RFM

The concept of relative mass is also used for ionic substances. The relative mass of an ionic substance
is called the relative formula mass, RFM. The relative formula mass is calculated by summing up
the relative atomic masses of all the atoms shown in the formula of the ionic substance. This is
because the mass of an ion does not differ much from the mass of its atom that forms the ion. Check
out Example 2.

Calculate the relative formula mass of zinc chloride, ZnCl2 and aluminium sulphate, Al2(SO4)3.
[Relative atomic mass: O = 16, Al = 27, S = 32, Cl = 35.5, Zn = 65]

Solution

RFM of zinc chloride, ZnCl2 = RAM of Zn + 2(RAM of Cl)
 = 65 + 2(35.5)
 = 65 + 71
 = 136
RFM of aluminium sulphate, Al2(SO4)3 = 2(RAM of Al) + 3[RAM of S + 4(RAM of O)]
 = 2(27) + 3[32 + 4(16)]
 = 54 + 3[96]
 = 342

Example 2

Activity 3.3
CT

Activity 3.4
CTTic-tac-toe with relative masses

Materials: 10 pieces of formula cards and a tic-tac-toe card
 1. Carry out the activity in pairs.
 2.  Each pair is given a tic-tac-toe card and 10 pieces of formula cards.

Each card has the formula of a specific substance and its relative mass.
 3.  Shuffle the cards and put them at the centre of the table with the

written side of the cards facing down.
 4.  The first player will take a piece of card. Without showing it to the second player, the first player

will read the formula of the substance on the card to the second player.

Calculating the relative molecular mass and relative formula mass

Determine the relative molecular mass or the relative formula mass of each of the following substances.
Refer to the Data Table of Elements on page 276 to obtain the relative atomic mass.
 1. H2  2. O3  3. CO  4. NH3  5. N2O4
 6. C4H10  7. CuCl2  8. Zn(OH)2  9. K2Cr2O7  10. Fe(NO3)3

Material for Activity 3.4

http://bit.ly/
2PeH6a5

48

THEME 2 Fundamentals of Chemistry
Mole Concept3.2

In our daily lives, we use units such as pairs and dozens to represent
the quantity or number of objects. Photograph 3.4, shows the objects
that can be quantified using the units pair and dozen. The unit pair
represents 2 objects while the unit dozen represents 12 objects.

Yourself
TestTest

3.1

Photograph 3.4 Uses of units in daily life

In the field of chemistry, we use the unit mole to measure the
amount of substance. What is the amount of substance represented
by the unit mole?

5.  Referring to the Data Table of Elements on page 276, the second player will calculate the relative
mass of the substance and show the answer to the first player. If the answer is correct, the second
player is allowed to mark the tic-tac-toe card. If the answer is wrong, the second player will lose
the chance to mark the tic-tac-toe card.

6.  Repeat steps 3 to 4 with the second player taking the card while the first player calculates the
relative mass of the substance.

7.  Continue to take turns until one of the players succeeds in marking a complete line vertically,
horizontally or diagonally or until all spaces are filled up.

1. Define relative atomic mass based on the carbon-12 scale.

2. Refer to the Data Table of Elements on page 276 to get the relative atomic masses.
  (a) How many atoms of lithium are required to equalise the mass of one atom of krypton?
  (b) How many atoms of helium are required to equalise the mass of a silver atom?

3.  Calculate the relative molecular mass or the relative formula mass of each of the following
substances:

(a) Methane, CH4  (c) Sulphuric acid, H2SO4

(b) Magnesium nitrate, Mg(NO3)2  (d) Formic acid, HCOOH

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
3.2.1 Define mole
3.2.2  Interrelate the Avogadro

constant, NA, the number
of particles and the

number of moles
3.2.3  State the meaning of

molar mass
3.2.4  Interrelate the molar

mass, mass and the
 number of moles
3.2.5  State the meaning of

molar volume
3.2.6  Interrelate the molar

volume, volume of gas
and the number of moles

3.2.7  Solve numerical
problems involving the
number of particles,
number of moles, mass
of the substances and
volume of gases

49

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Number of Moles and Number of Particles

The way to use mole is similar to the way of using the unit dozen.
For example, 2 dozens of pencils represent 2 × 12 or 24 pencils.
Similarly, the Avogadro constant, NA is used as the conversion
factor between the number of moles and the number of particles.

Number of moles, n = Number of particles
NA

Diagrammatically, the relationship between the number of
mole and the number of particles by using Avogadro constant as
the conversion factor is shown below:

Number of moles Number of particles
× NA

÷ NA

The Avogadro constant
is named after a famous
Italian scientist, Amedeo
Avogadro (1776 – 1856).

According to the International Union of Pure and Applied Chemistry (IUPAC), the new
definition of mole is as follows:

The mole, with the symbol mol, is the SI unit of amount of substance. One mole of substance
contains 6.02214076 × 1023 elementary entities of the substance. This number is a fixed value
known as the Avogadro constant, NA that is expressed in mol–1. The Avogadro constant, NA
is also called the Avogadro number.

The Avogadro constant, NA is defined as the number of particles
contained in one mole of substance, that is 6.02 × 1023 mol–1. In
other words, 1 mol of a substance contains 6.02 × 1023 particles
that form the substance. The type of particles depends on the type
of substance, namely atomic substance, molecular substance or
ionic substance as shown in Figure 3.6.

1 mol of copper, Cu
= 6.02 × 1023
   copper atoms, Cu

1 mol of an atomic substance contains
6.02 × 1023 atoms

Atomic
substance

Molecular
substance

1 mol of water, H2O
= 6.02 × 1023

H2O molecules

1 mol of a molecular substance contains
6.02 × 1023 molecules

Ionic
substance

1 mol of sodium
chloride, NaCl
= 6.02 × 1023
   NaCl units

1 mol of an ionic substance contains
6.02 × 1023 formula units

Figure 3.6 Numbers of particles in 1 mol of substance

For calculation at this level,
Avogadro constant, NA is
taken as 6.02 × 1023 mol–1,
to three significant figures.

50

THEME 2 Fundamentals of Chemistry
Activity 3.5
Calculating the number of moles and number of particles

[Avogadro constant, N
A

: 6.02 × 1023 mol–1]
 1. Calculate the number of atoms found in
  (a) 0.1 mol of carbon, C    (b) 3.5 mol of neon gas, Ne
 2. Calculate the number of molecules found in
  (a) 1.2 mol of hydrogen gas, H2     (b) 0.8 mol of ammonia, NH3
 3. Calculate the number of formula units found in
  (a) 3 mol of sodium chloride, NaCl    (b) 0.25 mol of potassium nitrate, KNO3

CT

The example of conversion between the number of mole and the number of particles by
using Avogadro constant, NA are shown in Examples 3, 4 and 5.

[Note: Assume Avogadro constant, NA: 6.02 × 1023 mol–1]

How many atoms are there in 0.2 mol of magnesium, Mg?

Solution

Number of magnesium atoms, Mg = 0.2 mol × 6.02 × 1023 mol–1

= 1.204 × 1023 atoms

Example 3

A sample of zinc chloride, ZnCl2 contains 3.01 × 1024 ZnCl2 units. Calculate the number of
moles of zinc chloride, ZnCl2 found in the sample.

Solution

Number of moles of zinc chloride, ZnCl2 = 3.01 × 1024

6.02 × 1023 mol–1

= 5 mol

Example 4

Use the equation:
Number of particles
= Number of moles × NA

Use the equation:
Number of moles

= Number of particles
NA

A gas jar is filled with 2 mol of oxygen gas, O2.
(a) How many molecules of oxygen are there in the gas jar?
(b) How many atoms of oxygen are there in the gas jar?

Solution

(a) Number of oxygen molecules, O2 = 2 mol × 6.02 × 1023 mol–1

= 1.204 × 1024 molecules
(b) Each oxygen molecule, O2 has 2 oxygen atoms, O.
 Hence, the number of oxygen atoms, O = Number of O2 molecules × 2
  = 1.204 × 1024 × 2
  = 2.408 × 1024 atoms

Example 5

Use the equation:
Number of particles
= Number of moles × NA

51

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Figure 3.7 Determining the molar mass of substances
  The mass of any fraction of a mole of a substance can be weighed. For example, 12 g of carbon
for 1 mol of carbon, 6 g of carbon powder for 0.5 mol of carbon and so on. The molar mass is used
as the conversion factor between the number of moles and the mass of substance. The formula and
the relationship between the number of moles and the mass of substance by using molar mass as
the conversion factor is as follows:

Number of moles, n = Mass (g)
Molar mass (g mol–1)

Number of moles Mass (g)
× Molar mass

÷ Molar mass

Why is g used as the unit for
mass in the formula?
Mass
= Number of moles × Molar mass
= mol × g

mol= g

Number of Moles and Mass of Substances

The number of moles of a substance is impossible to be determined by counting the number of
particles in the substance. Therefore, to get the number of moles, the mass of a substance must be
measured and we also need to know its molar mass. What is molar mass?

Molar mass is the mass of one mole of substance.

The unit for molar mass is gram/mol or g mol–1. Chemists found that the value of molar mass of
a substance is the same as its relative mass. For example, the relative atomic mass of carbon, C is 12.
Thus, the molar mass of carbon is 12 g mol–1 because 12 g of carbon, C contains 1 mol of carbon, C,
that is 6.02 × 1023 atoms of carbon, C. Look at Figure 3.7 to strengthen your understanding.

• Copper consists of
 copper atoms.
• RAM of copper = 64
• Molar mass of copper

= 64 g mol–1

• Water consists of H2O molecules.
• RMM of water = 2(1) + 16 = 18
• Molar mass of water = 18 g mol–1

• Sodium chloride consists of
NaCl units.

• RFM of sodium chloride
= 23 + 35.5 = 58.5

• Molar mass of sodium chloride
= 58.5 g mol–1

4. Calculate the number of moles of each of the following substances:
  (a) 6.02 × 1024 lead atoms, Pb    (c) 9.03 × 1022 bromine molecules, Br2
  (b) 3.02 × 1023 magnesium oxide units, MgO  (d) 3.612 × 1024 carbon dioxide molecules, CO2
 5. A reagent bottle contains 1.806 × 1025 units of copper(II) oxide, CuO.
  (a) How many moles of copper(II) oxide, CuO are found in the bottle?
  (b) Calculate the number of ions found in that bottle.
 6. A sample contains 0.2 mol of ethene gas, C2H4.
  (a) How many ethene molecules, C2H4 are found in the sample?
  (b) How many hydrogen atoms, H are found in the sample?
  (c) Calculate the total number of atoms found in the sample.

52

THEME 2 Fundamentals of Chemistry
Activity 3.6
Calculating the number of moles and mass

[Relative atomic mass: H = l, C = 12, N = 14, O = 16, Mg = 24, S = 32, Fe = 56;
Avogadro constant, N

A

: 6.02 × 1023 mol–1]
 1. Calculate the mass of each of the following substances:
  (a) 0.4 mol of iron fillings, Fe    (b) 2.2 mol of carbon monoxide, CO
 2. Calculate the number of moles in each of the following substances:
  (a) 49 g of sulphuric acid, H2SO4    (b) 8.88 g of magnesium nitrate, Mg(NO3)2

CT

What is the mass of 1.5 mol of aluminium, Al?
[Relative atomic mass: Al = 27]

Solution

Molar mass of aluminium, Al = 27 g mol–1
Mass of aluminium, Al = 1.5 mol × 27 g mol–1

= 40.5 g

Example 6

How many moles of molecules are found in 32 g of sulphur dioxide gas, SO2?
[Relative atomic mass: O = 16, S = 32]

Solution

Relative molecular mass of sulphur dioxide, SO2 = 32 + 2(16)
 = 64
Thus, the molar mass of sulphur dioxide, SO2 = 64 g mol–1
Number of moles of sulphur dioxide molecules, SO2 = 32 g

64 g mol–1

= 0.5 mol

Example 7

How many moles are found in 4.7 g of potassium oxide, K2O?
[Relative atomic mass: O = 16, K = 39]

Solution

Relative formula mass of potassium oxide, K2O = 2(39) + 16
 = 94
Thus, the molar mass of potassium oxide, K2O = 94 g mol–1

Number of moles of potassium oxide, K2O = 4.7 g
94 g mol–1

= 0.05 mol

Example 8

Examples of the conversion between the number of moles and the mass of the particles using
molar mass are shown in Examples 6, 7 and 8.

Value of the molar mass of an atomic
substance is equal to RAM.

Use the formula:
Mass = Number of moles × Molar mass

Value of the molar mass of a molecular
substance is equal to RMM.

Use the formula:
Number of moles = Mass

Molar mass

Value of the molar mass of an
ionic substance is equal to RFM.

Use the formula:
Number of moles = Mass

Molar mass

53

CHAPTER 3The Mole Concept, Chemical Formula and Equation
This means at STP,
•	 1	mol	of	neon	gas,	Ne	occupies	22.4	dm3

•	 1	mol	of	nitrogen	dioxide	gas,	NO2 occupies 22.4 dm3

While at room conditions,
•	 1	mol	of	neon	gas,	Ne	occupies	24	dm3

•	 1	mol	of	nitrogen	dioxide	gas,	NO2 occupies 24 dm3

How do we use the molar volume to measure the number
of moles of a gas? The formula and relationship between the
number of moles and the volume of gas by using molar volume
as a conversion factor are as follow:

Number of moles, n = Volume of gas
Molar volume

Number of moles Volume of gas
× Molar volume

÷ Molar volume

Number of Moles and Volume of Gases

Measuring the volume of a gas is easier compared to measuring its mass because gas is very light.
How are the number of moles and the volume of a gas related?

ChemistryChemistry

•  STP is the abbreviation
 for standard temperature
 and pressure, the condition
 where temperature is at 0 oC
 and pressure of 1 atm.
•  Room conditions refer
 to the condition where
 temperature is at 25 oC and
 pressure of 1 atm.

3.  An experiment requires 0.05 mol of ammonium sulphate crystals, (NH4)2SO4. What is the mass of
ammonium sulphate, (NH4)2SO4 that should be used?

4. 0.2 mol of substance Y has the mass of 11 g. What is the molar mass of substance Y?

Remember, the molar volume is
used only for gases and not for
solids or liquids.

Figure 3.8 Weighing the mass of a gas

From studies, chemists found that the volume
of 1 mol of any gas has similar value under the
same conditions of temperature and pressure. Thus,
the concept of molar volume was explained.

Molar volume is the volume occupied by 1 mol
of a gas. The molar volume of any gas depends
on the condition, that is  22.4 dm3 mol–1 at STP or
24 dm3 mol–1 at room conditions.

What is the mass of the
gas in this balloon?

The conversion between the number of moles and the volume of gas using molar volume are
shown in Examples 9, 10 and 11.

54

THEME 2 Fundamentals of Chemistry
Calculate the volume of 2.2 mol of hydrogen gas, H2 in dm3 at STP.
[Molar volume = 22.4 dm3 mol–1 at STP]
Solution

Volume of hydrogen gas, H2
= Number of moles × Molar volume at STP
= 2.2 mol × 22.4 dm3 mol–1

= 49.28 dm3

Example 9

What is the volume of 0.01 mol of ammonia gas, NH3 in cm3 at room conditions?
[Molar volume = 24 dm3 mol–1 at room conditions]
Solution

Volume of ammonia gas, NH3 = Number of moles × Molar volume at room conditions
 = 0.01 mol × 24 dm3 mol–1

= 0.24 dm3

= 0.24 × 1 000 cm3

= 240 cm3

Example 10

How many moles of oxygen gas, O2 has the volume of 600 cm3 at room conditions?
[Molar volume = 24 dm3 mol–1 at room conditions]
Solution

Volume of oxygen gas, O2 = 600 cm3

= 600
1 000  dm3

= 0.6 dm3

Number of moles of oxygen gas, O2 = Volume of gas
Molar volume at room conditions

= 0.6 dm3
24 dm3 mol–1

= 0.025 mol

Example 11

Activity 3.7
Calculating the number of moles and volume of gases

[Molar volume of gas = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]
 1. Calculate the volume of 0.6 mol of chlorine gas, Cl2 at STP and room conditions.
 2. Calculate the number of moles of each of the following gases:
  (a) 48 cm3 of argon gas, Ar at room conditions (b) 39.2 dm3 of carbon dioxide gas, CO2 at STP
 3.  A sample contains 0.2 mol of methane gas, CH4 and 0.3 mol of ethane gas, C2H6. What is the

volume of the sample at room conditions?

CT

Volume of gas
=  Number of moles × Molar

volume
= mol × dm3

mol
= dm3

Alternative
solution

http://bit.ly/
2MyrUmi

Convert unit of volume:
1 dm3 = 1 000 cm3

Convert unit of volume:
1 dm3 = 1 000 cm3

55

CHAPTER 3The Mole Concept, Chemical Formula and Equation
The relationship between the number of moles, number of particles, mass of substances and
volume of gases is shown in Figure 3.9.

Number of molesNumber of particles Volume of gas
× Molar volume× NA

÷ Molar volume÷ NA

Mass (g)

× Molar mass ÷ Molar mass

Figure 3.9 Relationship between the number of moles, number of particles, mass and volume of gases

Examples 12 and 13 show the function of the number of moles as a medium to convert from
one quantity to another.

Activity 3.8

What is the volume of 26.4 g of carbon dioxide, CO2 at room conditions?
[Relative atomic mass: C = 12, O = 16; Molar volume of gas = 24 dm3 mol–1 at room conditions]

Solution

Question analysis and solution plan

Information from the question: Mass = 26.4 g Volume of gas at room conditions?

Solution
plan

÷ Molar
mass

× Molar
volume

Step 1 Step 2

Number of moles

RMM of carbon dioxide, CO2 = 12 + 2(16)
 = 44
Thus, the molar mass of carbon dioxide, CO2 = 44 g mol–1

Number of moles of carbon dioxide, CO2 = Mass
Molar mass

= 26.4 g
44 g mol–1

= 0.6 mol

Example 12

Before carrying out step 1,
the molar mass must first
be determined.

Step 1:
Mass → Number of moles

Building a chart showing the relationship between the number of particles, number of

moles, mass of substances and volume of gases at STP and room conditions

1. Carry out the activity in groups.
 2.  Discuss among the group members and build a chart on a flip chart paper that shows the

relationship between the number of moles, number of particles, mass of substances and volume
of gases.

3. Each member needs to copy the chart onto a small, pocket-sized card to produce a memory card.
 4. Use this memory card to solve all the following numerical problems.

56

THEME 2 Fundamentals of Chemistry
Volume of carbon dioxide, CO2 = Number of moles × Molar volume
 = 0.6 mol × 24 dm3 mol–1

= 14.4 dm3

Hence, 26.4 g of carbon dioxide gas, CO2 occupies a volume of 14.4 dm3 at room conditions.

How many molecules are there in 672 cm3 of hydrogen gas, H2 at STP?
[Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP]

Solution

Question analysis and solution plan

Information from the question: Volume of gas = 672 cm3 Number of molecules?

Solution
plan

÷ Molar
volume

Step 1

× NA

Step 2

Number of moles

Number of moles of hydrogen gas, H2 = Volume of gas
Molar volume

= 672 cm3

22.4 × 1 000 cm3 mol–1

= 0.03 mol

Number of hydrogen molecules, H2 = Number of moles × NA

= 0.03 mol × 6.02 × 1023 mol–1

= 1.806 × 1022 molecules

Hence, 672 cm3 of hydrogen gas, H2 at STP consists of
1.806 × 1022 molecules.

Example 13

Further
example

http://bit.ly/
2MBDA7Z

Nandini, you need to determine
the number of moles of a
substance before determining
the number of particles, mass or
volume of a gas that is required.

Yes, teacher. I always refer
to my memory card from
Activity 3.8 to solve numerical
problems until I can really
understand and remember all
the relationships.

Step 2:
Number of moles → Volume

Step 1:
Volume → Number of moles

Step 2:
Number of moles →
Number of molecules

57

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Activity 3.9
Solving problems involving the number of particles, number of moles,

mass of substances and volume of gases at STP or room conditions

1. Carry out this activity in groups.
 2. Read and answer the following questions.
   [Relative atomic mass: H = 1, He = 4, C = 12, N = 14, O = 16, Al = 27, S = 32;

Avogadro constant, N
A

: 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1
at room conditions]

(a) Calculate the number of atoms found in the following substances:
   (i) 6.75 g of aluminium, Al    (ii) 5.1 g of ammonia gas, NH3

(b) Calculate the volume of the following gases at STP.
   (i) 5.6 g of nitrogen gas, N2    (ii) 1.204 × 1022 helium atoms, He
  (c)  What is the mass of oxygen gas, O2 that has the same number of molecules as in 8 g of sulphur

trioxide gas, SO3?
  (d)  A sample of methane gas, CH4 occupies a volume of 9.84 dm3 at room conditions. How many

molecules are found in that sample? Calculate the mass of the sample.
  (e)  A reaction releases 120 cm3 of carbon dioxide gas, CO2 per minute at room conditions.

Calculate the total mass of carbon dioxide, CO2 released after 10 minutes.
 3.  Write the calculation steps for questions (a) to (e) clearly and systematically on a piece of flip

chart paper.
 4. Present your group solution in front of the class.

Yourself
TestTest

3.2

CT

[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35.5, K = 39, Fe = 56,
Pb = 207; Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or
24 dm3 mol–1 at room conditions]
 1. Calculate the molar mass of each of the following substances:
  (a) Lead metal, Pb  (c) Sodium nitrate, NaNO3
  (b) Chloroform, CHCl3  (d) Iron(III) oxide, Fe2O3

2. Calculate the number of molecules found in 8 mol of water.
 3. What is the mass of 0.5 mol of ammonia, NH3?
 4. How many moles of K2O units are found in 14.1 g of potassium oxide, K2O?
 5. Calculate the volume of 16 g of oxygen gas, O2 at STP.

6.  The mass of 4 dm3 of a gas is 12 g at room conditions. Calculate the molar mass of
the gas.

7. 4 g of hydrogen gas, H2 has greater number of molecules than 14 g of nitrogen gas, N2

Do you agree with the above statement? Give your reason.

58

THEME 2 Fundamentals of Chemistry
Figure 3.10 Chemical formulae of elements and compounds

Chemical Formula3.3

Photograph 3.5 A chemical formula represents a
 chemical substance

Chemical formula is a representation of a chemical
substance using alphabets to represent the atoms and
subscript numbers to show the number of each type of
atoms found in the elementary entities of the substance.

Examples of chemical formulae of elements and compounds
are shown in Figure 3.10.

ChemistryChemistry

Elements are substances
that consist of only one
type of atoms. Elements like
metals and inert gases are
atomic substances while
elements such as oxygen gas
are molecular substances.

The subscript number 1
need not be written in a
chemical formula.

Ti spLiteracy

Elements

Compounds

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
3.3.1  State the meaning of

chemical formula,
empirical formula and
molecular formula

3.3.2  Determine the empirical
formula of magnesium
oxide, MgO through
an activity

3.3.3  Determine the empirical
formula of copper(II)
oxide, CuO through
an activity

3.3.4  Solve numerical
problems involving
empirical formula and
molecular formula

3.3.5  Construct chemical
formulae of compounds

Substance: Magnesium
Chemical formula: Mg

Substance: Oxygen gas
Chemical formula: O2

The chemical formula shows that
magnesium consists of magnesium
atoms only.

The chemical formula shows that
oxygen gas molecule consists of two
oxygen atoms.

Substance: Water
Chemical formula: H2O

Substance:
Aluminium oxide

Chemical formula: Al2O3

The subscript number shows that two
atoms of hydrogen combine with one
atom of oxygen.

The subscript number shows that two
atoms of aluminium combine with three
atoms of oxygen.

59

CHAPTER 3The Mole Concept, Chemical Formula and Equation
The empirical formula is the chemical formula that shows the simplest ratio of the number of
atoms of each element in a compound. The molecular formula, on the other hand, is the chemical
formula that shows the actual number of atoms of each element found in a molecule of a compound.
Figure 3.11 shows the difference between the empirical formula and the molecular formula.

Ratio of number of atoms
C atom : H atom : O atom
= 6 : 12 : 6
= 1 : 2 : 1

The formula shows one
molecule of glucose
consists of 6 carbon
atoms, 12 hydrogen atoms
and 6 oxygen atoms.

The formula shows that the
simplest ratio of the number
of carbon atoms to hydrogen
atoms and oxygen atoms
is 1:2:1.

Molecular formula of glucose:
C6H12O6

Empirical formula of glucose:
CH2O

Figure 3.11 Molecular formula and empirical formula of glucose

Table 3.3 Molecular formulae and empirical formulae of several substances

Empirical Formula and Molecular Formula

In general, compounds can be represented by two types of chemical formulae, namely the empirical
formula and the molecular formula. What are the empirical formula and the molecular formula?

TeaserBrain

Some compounds have the
same empirical formula
and molecular formula.
However, there are some
other compounds that have
different empirical formula
and molecular formula.
Try to think why it is so.

Substance Molecular formula Empirical formula

Water H2O H2O

Ammonia NH3 NH3

Hydrazine N2H4 NH2

Propene C3H6 CH2

Benzene C6H6 CH

Gathering and interpreting information involving chemical formulae,

empirical formulae and molecular formulae

1.  Carry out this activity in groups.
 2.  Gather information on chemical formulae, empirical formulae and molecular formulae by

referring to reading materials or surfing the Internet.
 3.  Based on the information gathered, construct a suitable thinking map to show the difference

between the empirical formula and the molecular formula using a suitable computer software.
 4.  List out the examples of chemical formulae in a table and use this list throughout your lesson.

Activity 3.10
CT

60

THEME 2 Fundamentals of Chemistry
Determination of an Empirical Formula

The empirical formula is obtained by the analysis of percentage
composition of a substance. This is done by determining the
simplest whole number ratio of atoms of each element that
combines through an experiment. Example 14 is used as a guide to
solve Activity 3.11.

Using the calculation skills learned, the determination of the empirical formulae of magnesium
oxide and copper(II) oxide can be carried out through Activity 3.12 and 3.13.

1.35 g of aluminium combines with 1.2 g of oxygen to form aluminium oxide.
What is the empirical formula of aluminium oxide?
[Relative atomic mass: O = 16; Al = 27]

Solution

n = Mass
Molar mass

Divide each number with the
smallest number, that is 0.05.

Multiply each answer by 2 to get the simplest
whole number ratio.

Element Al O

Mass (g)   1.35 1.2
Number of moles
of atoms

1.35
27  = 0.05 1.2

16  = 0.075

Mole ratio 0.05
0.05  = 1 0.075

0.05  = 1.5

Simplest mole ratio
of atom 2 3

Determine the mass of each element.

2 mol of aluminium atoms combine with 3 mol of oxygen atoms.
Thus, the empirical formula of aluminium oxide is Al2O3.

Example 14

Activity 3.11
Determining the empirical formulae

[Relative atomic mass: H = 1, C = 12, O = 16, Cl = 35.5, K = 39, Br = 80, Sn = 119, I = 127]
 1.  A sample of potassium bromide contains 6.24 g of potassium and 12.8 g of bromine. What is the

empirical formula of potassium bromide?
 2.  A sample of 26.1 g of tin chloride contains 11.9 g of tin. State the empirical formula of the

tin chloride.
 3.  0.03 mol of element Y combines with 7.62 g of iodine to produce

an iodide salt. State the empirical formula of the iodide salt.
 4.  A chemist analysed the compound that gives smell to fully ripe

bananas. He found that the compound contains 64.62% carbon,
10.77% hydrogen and 24.61% oxygen. What is the empirical formula
of that compound? Photograph 3.6 Bananas

TeaserBrain

TeaserBrain

Hexane is an organic solvent
that is widely used in the
food industry. The molecular
formula of hexane is C6H14.
What is its empirical formula?

CT

61

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Activity 3.12

Prevent white fumes in the
crucible from escaping when
carrying out Step 7.

Safety Precaution

Prepare a complete report after carrying out this activity.

Aim: To determine the empirical formula of magnesium oxide.
Materials: 10 cm magnesium ribbon and sand paper
Apparatus: Crucible with lid, tongs, Bunsen burner, tripod stand, pipeclay triangle and

electronic balance

Procedure:

1.  Weigh and record the mass of a crucible together
with its lid.

2.  Rub 10 cm magnesium ribbon with a sand paper
until shiny. Coil the magnesium ribbon and put it in
the crucible.

3.  Weigh and record the mass of the crucible together
with its lid and the coil of magnesium ribbon.

4. Set up the apparatus as shown in Figure 3.12.
 5. First, heat the crucible without its lid.
 6.  When magnesium ribbon starts to burn, close the crucible

with its lid.
 7.  Using a pair of tongs, lift the lid slightly from time to time

and quickly place it back.
 8.  When the burning of magnesium ribbon is complete, take off the

lid and heat the crucible with high temperature for 1 to 2 minutes.
 9. Put back the lid of the crucible and allow it to cool to room temperature.
 10. Weigh the mass of crucible together with its lid and its contents again.
 11. Repeat the heating, cooling and weighing process until a constant mass is obtained.
 12. Record the constant mass in Table 3.4.

Results:

Table 3.4

Description Mass (g)
Crucible +  lid
Crucible +  lid +  magnesium ribbon
Crucible +  lid +  magnesium oxide

Interpreting data:

1. Based on your results, determine the masses of magnesium and oxygen that combine.
 2. Determine the empirical formula of magnesium oxide.

Discussion:

1. What is the purpose of rubbing the magnesium ribbon with a sand paper before using it?
 2. Name the white fumes that are produced.
 3. Why are steps 6, 7 and 11 performed?
 4. What will happen if the white fumes are released into the environment?

Heat

Magnesium
ribbon
Pipeclay triangle

Crucible

Lid

Figure 3.12

62

THEME 2 Fundamentals of Chemistry
Activity 3.13
Aim: To determine the empirical formula of copper(II) oxide.
Materials:  Water, copper(II) oxide powder, zinc granules, 1.0 mol dm–3 hydrochloric acid, wooden

splinter and cotton buds
Apparatus:  Boiling tube, rubber stoppers, rubber tube, 12 cm glass tube, 10 cm glass tube, spirit

lamp, retort stand with clamp, wooden block, electronic balance and spatula
Procedure:

1. Weigh the mass of 12 cm glass tube using an electronic
balance and record its mass.

2. Put some copper(II) oxide powder into the glass tube.
Use the wooden splinter to move copper(II) oxide powder
to the middle of the glass tube. Weigh the mass of the
glass tube together with its contents and record the mass.

3. Fill 2
3  of the boiling tube with water.

4. Close the boiling tube with a rubber stopper that has a 12 cm glass tube. Clamp the boiling
tube onto the retort stand.

5. Insert a few zinc granules into another boiling tube. Add 1.0 mol dm–3 hydrochloric acid into
the boiling tube until it is 1

3  full.
 6. Close the boiling tube with a rubber stopper that has a 10 cm glass tube. Clamp the boiling

tube onto the other retort stand.
 7. Connect the glass tube that contains copper(II) oxide powder as shown in Figure 3.13.

Glass tube
(10 cm)

Rubber
tube

Glass tube (12 cm)

Glass tube
(12 cm)

Ethanol

Water

Zinc granules

Wooden block

1.0 mol dm–3

Copper(II) oxide powder

Air
opening

hydrochloric acid

Figure 3.13
 8. Let the hydrogen gas flow for 10 seconds by allowing the air

bubbles to be released in the water before starting the
heating process.

9. Heat copper(II) oxide using a spirit lamp with a continuous
flow of hydrogen gas through the glass tube.

10. Stop the heating when the black colour of copper(II) oxide
turns brown completely.

11. Keep a continuous flow of hydrogen gas until the glass tube is
cooled back to room temperature.

If necessary, hold the spirit
lamp by moving it under
the glass tube to heat the
remaining powder that is
still black so that all black
powder turns brown.

Safety Precaution

Guideline to determine
the empirical formula
of copper(II) oxide

http://bit.ly/2VLQHq6

63

CHAPTER 3The Mole Concept, Chemical Formula and Equation
12. Remove the glass tube that contains brown powder. Eliminate
water drops at the end of the glass tube with a cotton bud.

13.  Weigh the mass of the glass tube together with its contents
and record its mass.

14. Repeat the heating, cooling and weighing processes from
steps 9 to 13 until a constant mass reading is obtained.

15. Record the constant mass in Table 3.5.

Results:

Table 3.5

Description Mass (g)

Glass tube

Glass tube + copper(II) oxide

Glass tube + copper

Copper

Oxygen

Interpreting data:

1. Determine the empirical formula of copper(II) oxide in this activity.

Discussion:

1. What is the purpose of using zinc granules and hydrochloric acid in this activity?
 2. Why does the hydrogen gas need to flow continuously for a while before starting the

heating process?
 3. The hydrogen gas is allowed to flow until the product of heating is at room temperature in

step 11. Why?
 4. Why do the heating, cooling and weighing processes need to be repeated until a constant

mass is obtained?

For reactive metals like magnesium, the metal needs to be heated only slightly before it can
react with the oxygen in the air. Figure 3.14 shows how the mass of magnesium and oxygen that
combine are calculated to determine the simplest mole ratio of atom.
 Can you name another reactive metal oxide which empirical formula can be determined
using the same method?

Magnesium + Oxygen ˜ Magnesium oxide

This mass is determined before
the reaction takes place.

This mass is determined
after the reaction takes place.

This mass is calculated as the difference
between the masses of magnesium and
magnesium oxide.

Figure 3.14 Calculation of the mass of magnesium and oxygen in magnesium oxide

Prepare a complete report after carrying out this activity.

Another method of
determining the empirical
formula of
copper(II) oxide

http://bit.ly/
2BeHBbY

64

THEME 2 Fundamentals of Chemistry
However, this method is not suitable in determining the empirical
formula of copper(II) oxide because copper is less reactive towards
oxygen. Hence, copper(II) oxide is heated in a stream of hydrogen
gas so that hydrogen can remove oxygen from the oxide as shown
in Figure 3.15.

Copper(II) oxide + Hydrogen ˜ Copper + Water

This mass is determined
 before the reaction takes place.

This mass is determined
 after the reaction takes place.

The mass of oxygen is calculated as the
 difference between the masses of copper(II)
oxide and copper.

Figure 3.15 Calculation of the masses of copper and oxygen in copper(II) oxide

Determination of a Molecular Formula

The molecular formula of a compound is its multiplied empirical formula.

Molecular formula = (Empirical formula)n

The value of n is a positive integer. Table 3.6 shows several examples.

Table 3.6 Relationship between the molecular formula and the empirical formula

Substance Water Hydrazine  Propene Benzene

Empirical formula H2O NH2 CH2 CH

Molecular formula (H2O)1= H2O  (NH2)2 = N2H4 (CH2)3 =   C3H6 (CH)6 = C6H6

n 1 2 3 6

Therefore, to determine the molecular formula of a compound, we first need to know its
empirical formula. Examples 15 and 16 show solutions regarding chemical formula.

Reactivity series
of metals

http://bit.ly/
2pFVTQb

A compound has the empirical formula CH2. Its relative molecular mass is 56. What is the
molecular formula of the compound? [Relative atomic mass: H = 1; C = 12]

Solution

Assume that the molecular formula of the compound is (CH2)n.
Based on its molecular formula, the RMM of compound = n[12 + 2(1)]
 = 14n
Given the RMM of compound, 14n = 56
 n = 56

14
  = 4
Hence, the molecular formula of the compound is C4H8.

Example 15

Equate the calculated RMM
with the given one.

65

CHAPTER 3The Mole Concept, Chemical Formula and Equation
1.2 g of element Y reacts with bromine to form 6 g of a compound with the empirical formula
YBr2. Determine the relative atomic mass of Y. [Relative atomic mass: Br = 80]
Solution

The compound consists of element Y and bromine.
Therefore, the mass of element Y + mass of bromine  = mass of compound formed
 1.2 g + mass of bromine = 6 g
 Mass of bromine = (6 − 1.2) g
  = 4.8 g
Assume that the RAM of element Y is x.

Element Y Br

Mass (g) 1.2 4.8
Number of moles
of atoms

1.2
x  = ? 4.8

80  = 0.06

Based on the empirical formula YBr2,
2 mol of Br atoms combine with 1 mol of atom Y or
1 mol of Br atoms combine with 0.5 mol of atom Y or
0.06 mol of Br atoms combine with 0.03 mol of atom Y.
 Hence, the number of moles of atom Y that reacts = 0.03 mol
 1.2

x  = 0.03
 x = 1.2

0.03
  = 40
The RAM of element Y is 40.

Activity 3.14
CT

Example 16

Further
example

http://bit.ly/
32BiQ5J

Based on the empirical formula,
calculate using the right ratio.

Solving numerical problems involving empirical formulae and

molecular formulae

[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Ca = 40, Zn = 65]
 1.  Ethanoic acid has a molar mass of 60 g mol–1. If its empirical formula is CH2O, determine the

molecular formula of ethanoic acid.
 2.  Hydrocarbons consist of carbon and hydrogen. 5.7 g of a hydrocarbon contains 4.8 g of carbon.

If the relative molecular mass of the hydrocarbon is 114, determine its molecular formula.
 3.  What is the mass of zinc required to combine with 0.5 mol of chlorine to produce zinc

chloride, ZnCl2?
 4.  Assume you are a farmer. You want to choose a fertiliser with a high nitrogen content for your

plants. Three types of commonly used fertilisers are as follows.

Ammonium nitrate, NH4NO3
Urea, CO(NH2)2

Nitrosol, Ca(NO3)2

Which fertiliser would you choose? Give reasons for your choice. Show the steps used in
the calculation.

66

THEME 2 Fundamentals of Chemistry
Chemical Formulae of Ionic Compounds

Ionic compounds are made up of cations (positively-charged ions) and anions (negatively-charged
ions). In order to write the chemical formulae of ionic compounds, you need to know the formulae
of cations and anions. Table 3.7 shows the examples of formulae for cations and anions that are
commonly used. Figure 3.16 explains how the chemical formula of an ionic compound is constructed.

Table 3.7 Formulae of common cations and anions

Anion Formula of anion

Oxide ion O2–

Chloride ion Cl–

Bromide ion Br–

Iodide ion I–

Hydroxide ion OH–

Carbonate ion CO3
2–

Nitrate ion NO3
–

Sulphate ion SO4
2–

Phosphate ion PO4
3–

Manganate(VII) ion MnO4
–

Thiosulphate ion S2O3
2–

Dichromate(VI) ion Cr2O7
2–

Cation Formula of cation

Sodium ion Na+

Potassium ion K+

Aluminium ion Al3+

Zinc ion Zn2+

Magnesium ion Mg2+

Iron(II) ion Fe2+

Iron(III) ion Fe3+

Copper(II) ion Cu2+

Calcium ion Ca2+

Silver ion Ag+

Lead(II) ion Pb2+

Ammonium ion NH4
+

Name: Zinc chloride

Figure 3.16  Constructing the chemical formula of
zinc chloride via cross-change method

Formula: ZnCl2
The basic concept of
constructing a chemical
formula of an ionic
compound

http://bit.ly/
35WMLam

Further example on
cross-change method

http://bit.ly/
32DGbUu

3. Write the chemical
formula of the
compound.
The formula is
neutral. The
charges of ions
are not written in
the formula. The
subscript number
is used to show the
number of ions.

Cl–

Cl–

Zn2+

Zn2+

Cation: Zinc ion Anion: Chloride ion

Check: Positive charge : 1 × (+2) = +2
 Negative charge : 2 × (–1) = –2
 Total charge :  0

1 2

The number of ion:

1. Based on the name of the compound,
determine the cation and anion.

2. Cross-change the cation charge and anion charge
to determine the number of cations and anions.

67

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Naming of Chemical Compounds

For ionic compounds, the name of the cation is written first
followed by the name of the anion as in Table 3.8.

Table 3.8 Examples in the naming of ionic compounds

Cation Anion Name of ionic compound

Sodium ion Chloride ion Sodium chloride

Zinc ion Bromide ion Zinc bromide

Magnesium ion Nitrate ion Magnesium nitrate

Some metals form more than one type of ions. In order to distinguish these ions, Roman
numerals are used in their naming. For example, iron forms two types of cations, namely Fe2+ and
Fe3+. Fe2+ ion is named as iron(II) ion while Fe3+ ion is named as iron(III) ion. Take a look at the
names of the following compounds:

Shows iron(III)
ion, Fe3+

Shows iron(II)
ion, Fe2+ Iron(II) oxide

Iron(III) oxide

When naming simple molecular compounds, the more electropositive element is named first
followed by the name of the more electronegative element. The name of the first element remains
the same while the second element ends with ‘ide’. Greek prefixes are used to represent the number
of atoms of each element in simple molecular compounds. Look at the examples below.

CO – Carbon monoxide
NO2 – Nitrogen dioxide
SO3 – Sulphur trioxide

Greek prefixes like
‘mono’, ‘di’ and ‘tri’ show
the numbers one, two
and three respectively.

Activity 3.15
Constructing the chemical formulae of ionic compounds

1. Carry out this activity individually.
 2. Scan the QR code and download the diagram of ionic formula cards.
 3. Print and cut out the ionic formula cards.
 4.  Use the ion formula cards to help you determine the chemical

formula of each of the following ionic compounds:

Potassium oxide Sodium hydroxide Magnesium nitrate Calcium nitrate
Sodium chloride Aluminium oxide Potassium carbonate Aluminium chloride
Calcium bromide Zinc sulphate Copper(II) sulphate Sodium carbonate

5. Record your answers systematically in a table.

CT

Other Greek prefixes are as
follows:
tetra – 4  hex – 6
pent – 5  hept – 7

Ti spLiteracy

ChemistryChemistry

Chemical compounds
are named systematically
as recommended by the
International Union of
Pure and Applied
Chemistry (IUPAC).

Diagram of ionic
formula cards

http://bit.ly/
2N4JVaG

68

THEME 2 Fundamentals of Chemistry
Photograph 3.7 Burning of an oil lamp

Did you know that the burning of fuel and the digestion of food in our bodies are all chemical
reactions? Chemists have a simple and accurate way to describe chemical reactions, that is through
chemical equations.

Activity 3.16

Yourself
TestTest

3.3

Chemical Equation3.4

CTNaming compounds

1.  Name the ionic compounds with the following formulae:
  (a) CaCl2  (c) Mg(NO3)2  (e) Na2SO4
  (b) KBr  (d) ZnCO3  (f) NH4Cl
 2.  Name the molecular compounds with the following formulae:
  (a) NO  (c) SO3  (e) BF3
  (b) CO2  (d) CCl4  (f) CS2

3.  The molecule of a compound consists of two nitrogen atoms and three oxygen atoms.
Name the compound.

1. What is meant by empirical formula and molecular formula?

2.  Caffeine, C8H10N4O2 is a natural stimulant found in coffee, tea and cocoa. What is the
empirical formula of caffeine?

3.  Calcium carbonate and sodium fluoride are two compounds found in toothpaste. Write the
chemical formulae of both compounds.

4.  A sample of 5.04 g of oxide for phosphorus contains 2.48 g of phosphorus.
[Relative atomic mass: O = 16, F = 31]

(a)  If the relative molecular mass of the oxide is 126, determine its empirical formula and
molecular formula.

(b)  Name the oxide of the phosphorus.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
3.4.1  Write balanced

chemical equations
3.4.2  Interpret chemical

equations quantitatively
and qualitatively

3.4.3  Solve stoichiometry
numerical problems

69

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Activity 3.17
Balancing chemical equations

1. Write a balanced chemical equation for each of the following reactions:
  (a) Nitrogen gas + Hydrogen gas → Ammonia gas
  (b) Sodium metal + Water → Aqueous solution of sodium hydroxide + Hydrogen gas
  (c)  Solid copper(II) carbonate decomposes into solid copper(II) oxide and carbon dioxide gas

when heated.
  (d)  Burning of aluminium powder in excess oxygen produces

white aluminium oxide powder.

2. Balance the following chemical equations:
  (a) KI(aq) + Br2(aq) → I2(s) + KBr(aq)
  (b) Zn(s) + AgNO3(aq) → Zn(NO3)2(aq) + Ag(s)
  (c) C3H8(g) + O2(g) → CO2(g) + H2O(l)
  (d) AgNO3(s)→Ag(s) + NO2(g) + O2(g)

CT

How to Write Chemical Equations

Chemical equations can be written in the form of words or using chemical formulae. The starting
substances or reactants are written on the left-hand side of the equation while the new substances
formed or products are written on the right-hand side of the equation. The arrow ‘→’ means
‘produces’. The physical state of each substance, whether solid(s), liquid(l), gas(g) or aqueous
solution(aq) is usually indicated in a chemical equation. Figure 3.17 shows the examples of writing
the chemical equation for the reaction between hydrogen and oxygen.

ChemistryChemistry

Sometimes, chemical
equations also show the
condition of the reactions.
For example, the Greek
letter delta (Δ) below the
arrow shows that heating
is required in the
chemical reaction.

Chemical equations need to be balanced. Based on the
law of conservation of mass, matter can neither be created
nor destroyed. Therefore, the number of atoms of each
element on both sides of the equation must be the same.

Δ

Figure 3.17 Writing the chemical equation for the reaction between hydrogen and oxygen

Reactants

Hydrogen + →

→

→

→

→

Oxygen

Product

Water

H2 + O2 H2O

H2 + O2
 (2 H atoms)   (2 O atoms)

H2O
(2 H atoms, 1 O atom)

Equation is not balanced

2H2 + O2
 (4 H atoms)   (2 O atoms)

2H2O
(4 H atoms, 2 O atoms)

2H2(g) + O2(g) 2H2 O(l)

1. Write the equation in words.

2. Write down the chemical formula of
each reactant and product.

3. Check whether the equation is balanced.

5. Write the physical state of each
reactant and product.

4.  Balance the equation by adjusting the
 in front of the chemical formula.

Simulation on balancing
chemical equation

http://bit.ly/33vr5QQ

70

THEME 2 Fundamentals of Chemistry
Aim: To write balanced chemical equations.
Materials:  Copper(II) carbonate powder, CuCO3, concentrated

hydrochloric acid, HCl, concentrated ammonia
solution, NH3, lead(II) nitrate solution, Pb(NO3)2,
potassium iodide solution, KI and limewater

Apparatus:  Test tubes, delivery tube and rubber stopper, test tube
holder, Bunsen burner, 10 cm3 measuring cyclinder,
test tube stoppers and glass tube

Procedure:

Heating of copper(II) carbonate, CuCO
3

1.  Fill a spatula of copper(II) carbonate powder, CuCO3 into a
test tube. Observe the colour of the powder.

2. Set up the apparatus as shown in Figure 3.18.
 3.  Heat copper(II) carbonate, CuCO3 and let the gas produced flow into

the test tube filled with limewater. Observe the changes that take
place in both test tubes.

4.  When the reaction is completed, remove the test tube of limewater.
Then, stop the heating.

5. Record your observations.

Formation of ammonium chloride, NH
4

Cl

1.  Using a glass tube, put 3 or 4 drops of concentrated hydrochloric
acid, HCl into a test tube. Close the test tube with a stopper and
leave it for a few minutes.

2.  Repeat step 1 using concentrated ammonia solution, NH3 in
another test tube.

3.  Remove the stoppers from both test tubes. Quickly bring the
mouths of both test tubes together as shown in Figure 3.19.

4. Observe and record the changes that take place.

Precipitation of lead(II) iodide, PbI
2

1. Pour 2 cm3 of lead(II) nitrate solution, Pb(NO3)2 into a test tube.
 2. Pour 2 cm3 of potassium iodide solution, KI into another test tube.
 3.  Pour potassium iodide solution, KI into lead(II) nitrate

solution, Pb(NO3)2 as shown in Figure 3.20. Shake the mixture.
 4. Observe and record the changes that take place.

Discussion:

1. For each reaction in experiments A, B and C, state:
  (a) The reactants and products
  (b) The physical state of each reactant and product
  (c) The chemical formula of each reactant and product
 2. Write a balanced chemical equation for each of the reactions.

Activity 3.18

Figure 3.18

Heat

Copper(II) carbonate powder

Limewater

Figure 3.19

Hydrogen
chloride
gas

Ammonia
gas

Figure 3.20

Lead(II) nitrate
solution

Potassium iodide
solution

Concentrated hydrochloric
acid and concentrated
ammonia are corrosive.
Handle them with care and
carry out Activity 3.18 in the
fume chamber.

Prepare a complete report after carrying out this activity.

71

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Using Chemical Equations

Chemical equation can be interpreted qualitatively and quantitatively. From the qualitative aspect,
chemical equations enable us to identify the reactants and products as well as their physical states.

2Na(s)  + Cl2(g)  2NaCl(s)

Reactants: Sodium metal and chlorine gas  Product: Solid sodium chloride

→

From the quantitative aspect, we can study the stoichiometry of chemical equations.
Stoichiometry is the quantitative study of the composition of substances involved in a chemical
reaction. Coefficients in chemical equations show the ratio of substances involved, either as the
ratio of elementary entities of substance or the mole ratio. Take a look at the following example:

Ratio of basic entities (particles):
Two sodium atoms react with one molecule of
chlorine to produce two NaCl units.

Mole ratio:
2 mol of sodium react with 1 mol of chlorine gas to
produce 2 mol of sodium chloride.

2Na(s)   +  Cl2(g)  2NaCl(s)
(2 atoms)   (1 molecule)  (2 formula units)

or  or  or

(2 mol) (1 mol) (2 mol)

→

Based on the mole ratio of substances from a balanced chemical equation, we can solve various
numerical problems by calculating the number of moles of substances required in the right ratio.

2Na(s)   + →  Cl2(g)    2NaCl(s)

(2 mol) (1 mol) (2 mol)
(1 mol)  (1 mol)

Initial mole ratio from the stoichiometry

All values are divided by 2

Calculated in the right ratio for other values

(0.5 mol)

Activity 3.19

Interpreting chemical equations qualitatively and quantitatively

1. Carry out the Think-Pair-Share activity.
 2.  Based on the chemical equations obtained from Activity 3.18, interpret each equation qualitatively

and quantitatively, from the aspects of ratio of elementary entities and mole ratio.
 3. Discuss with your partner.
 4. Share the results of your discussion with the class.

Century
Skills21st

72

THEME 2 Fundamentals of Chemistry
Activity 3.20
CT

The number of moles determined can be converted to mass, number of particles or volume of
gas using the molar mass, Avogadro constant or molar volume like all the relationships you have
learned before.

Burning of aluminium in air is as follows:

4Al(s) + 3O2(g) → 2Al2O3(s)

What is the mass of aluminium oxide produced if 5.4 g of aluminium is burnt completely in air?
[Relative atomic mass: O = 16, Al = 27]
Solution

Question analysis and solution plan
Equation:  4Al(s)  + 3O2(g) → 2Al2O3(s)
Information from the equation:  (4 mol)  (2 mol)
Information from the question:  (5.4 g) (? g – question to be answered)

Step 1 Step 2 Step 3

How many moles? Mole ratio? What is the mass?

Number of moles in 5.4 g of aluminium, Al = Mass
Molar mass

=
5.4 g

27 g mol−1

= 0.2 mol
Based on the equation, 4 mol of aluminium, Al produces 2 mol
of aluminium oxide, Al2O3. Therefore, 0.2 mol of aluminium,
Al produces 0.1 mol of aluminium oxide, Al2O3.
Hence, the mass of aluminium oxide, Al2O3 produced
= Number of moles × Molar mass
= 0.1 mol × [2(27) + 3(16)] g mol–1

= 0.1 mol × 102 g mol–1

= 10.2 g

Example 17

Step 1:
Mass of Al → Number of moles of Al

Step 2:
Calculate the mole ratio of Al2O3.

Step 3:
Number of moles of Al2O3 → Mass of Al2O3

Solving numerical stoichiometry problems

[Relative atomic mass: H = 1, C = 12, O = 16, Cl = 35.5, Ca = 40, Fe = 56, Zn = 65;
Avogadro constant, N

A

: 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1
at room conditions]
 1. Decomposition of calcium carbonate by heating is as follows:

CaCO3(s) → CaO(s) + CO2(g)

What is the mass of calcium carbonate required to produce 1.2 dm3 of carbon dioxide gas, CO2
at room conditions?

Δ

73

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Activity 3.21

Yourself
TestTest

3.4

2. Zinc reacts with hydrochloric acid as follows:
 Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
  What is the mass of zinc that should be used to produce 0.5 mol of hydrogen gas, H2?
 3.  A sample of iron(III) oxide, Fe2O3 is heated in a stream of excess hydrogen gas, H2 to produce

5.6 g of iron metal according to the following equation:
 Fe2O3(g) + 3H2(g) → 2Fe(s) + 3H2O(l)
  Calculate the mass of the iron(III) oxide sample.
 4. Nitrogen and hydrogen gases react according to the following equation:
 N2(g) + 3H2(g) → 2NH3(g)
   How many molecules of ammonia, NH3 are produced if 6.72 dm3 of nitrogen gas at STP reacts

completely with hydrogen gas?

Creating a computer worksheet

Decomposition of potassium chlorate(V), KClO3 by heat is often used to produce oxygen gas in
the laboratory.

2KClO3(s) → 2KCl(s) + 3O2(g)

Assume you are a laboratory assistant. You are required to prepare different amounts of oxygen
gas from time to time. Repeated calculations using chemical equations can be simplified using a
computer worksheet. Use Microsoft Excel or other suitable programmes to prepare a computer
worksheet involving the equation above to solve the following problems:
[Relative atomic mass: O = 16, Cl = 35.5, K = 39; Molar volume = 24 dm3 mol–1 at room conditions]

1.  What are the masses of potassium chlorate(V), KClO3 needed to produce 1 dm3, 5 dm3, 10 dm3,
20 dm3 and 50 dm3 of oxygen gas?

2.  What are the volumes of oxygen gas produced if 0.25 kg, 0.5 kg, 1 kg, 1.5 kg and 2 kg of
potassium chlorate(V), KClO3 are used?

1. Write the chemical equations for the following reactions:
  (a) Copper + Silver nitrate solution → Copper(II) nitrate solution + Silver
  (b) Hot zinc metal will react with chlorine gas to produce solid zinc chloride
 2. Decomposition of hydrogen peroxide, H2O2 occurs according to the following equation:
 2H2O2(l) → 2H2O(l) + O2(g)
  (a) What are the products of the decomposition of hydrogen peroxide, H2O2?
  (b)  Calculate the volume of oxygen produced at STP from the decomposition of 30.6 g of

hydrogen peroxide, H2O2.

CT

74

THEME 2 Fundamentals of Chemistry
importance consists of

typesinformation obtained

÷  molar
volume

÷ NA
involved in the
calculations of

Molecular formula

Mass (g)

Relative atomic mass

Relative molecular mass

Relative formula mass

Relative mass

Number of particles

Number of Moles, n

Chemical Equation

Chemical Formula

Concept

Stoichiometry

÷  molar
mass

×  molar
volume

× NA

×  molar
mass

Volume of gas

QuickQuick

http://bit.ly/
31DFXv1

Self Reflection

1. What is interesting about The Mole Concept, Chemical Formula and Equation?
 2.  Why is the learning of The Mole Concept, Chemical Formula and Equation important in

the next chemistry lesson?
 3.  Rate your performance in The Mole Concept, Chemical Formula and Equation on a scale

of 1 to 10; 1 being the lowest and 10 the highest. Why would you rate yourself at that level?
 4.  What can you do to improve your mastery in The Mole Concept,

Chemical Formula and Equation?
 5.  What else would you like to know about The Mole Concept,

Chemical Formula and Equation?
http://bit.ly/
2MiTOlY

Empirical formula

75

CHAPTER 3The Mole Concept, Chemical Formula and Equation
Achievement 3
Refer to the Data Table of Elements on page 276.
[Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1
at room conditions]

1. What is meant by molar mass and molar volume?

2.  What is the relationship between Avogadro constant, number of particles and number of moles?

3. Relative atomic mass of nitrogen is 14

State the meaning of the above statement based on the carbon-12 scale.

4.  Vitamin C or ascorbic acid is an important antioxidant required for our health. Vitamin C has
the molecular formula C6H8O6.

(a) What is the empirical formula of vitamin C?
  (b) What is the relative molecular mass of vitamin C?

5.  Antacid functions to relieve gastric problems. Figure 1 shows the label on a bottle of antacid.

In
gr

ed
ie

nt
s

ReliefRelief
Antacid
Aluminium hydroxide 160 mg
Magnesium carbonate 105 mg

Relieves flatulence
 Relieves heartburn

100
Tablets A

ct
iv

e
su

bs
ta

nc
e

(p
er

ta
bl

et
)

F
un

ct
io

n
A

lu
m

in
iu

m
 h

yd
ro

xi
de

1
60

m
g

..
...

...
..

A
nt

ac
id

M
ag

ne
si

um
 c

ar
bo

na
te

1
05

m
g

..
...

...
.A

nt
ac

id

Figure 1

Give the chemical formulae of the two active ingredients in the antacid.

6.  Figure 2 shows the aerobic respiration in our body cells to
produce energy from glucose, C6H12O6. Write a balanced
chemical equation for the process of aerobic respiration.

7.  Iron(II) sulphate heptahydrate, FeSO4.7H2O is often used to treat anaemic patients suffering
from the lack of iron mineral.

(a)  What is the molar mass of iron(II) sulphate heptahydrate?
  (b)  Calculate the percentage of iron in iron(II) sulphate heptahydrate.

Glucose + Oxygen

Glucose Oxygen

Carbon dioxide + Water

Carbon dioxide
Figure 2

76

THEME 2 Fundamentals of Chemistry
8.  Figure 3 shows the weighing steps taken in the determination of the empirical formula of the
oxide of metal Y.

ON
OFF  230.3024 g

Porcelain boat Metal Y oxide

Combustion tube

ON
OFF  242.2501 g

Metal Y

ON
OFF  240.6444 g

Figure 3

Determine the empirical formula of metal Y oxide.
  [Relative atomic mass: O = 16, Y = 207]

9.  P, Q and R are three samples of chemical substances.

P – 0.2 mol of calcium chloride
Q –  12 dm3 of nitrogen monoxide gas at

room conditions
R – 2.408 × 1023 carbon dioxide molecules

Arrange the three samples in ascending order of mass.

10.  In your opinion, between the empirical formula and the molecular formula, which formula is
more suitable to be used when writing chemical equations? Give your reasons.

Check   AnswersAnswers

https://bit.ly/
32OHQGV

CornerEnrichmen

1.  When steam is passed over a hot iron metal, hydrogen gas and iron(III) oxide are formed.
What is the mass of steam required to react completely with 100 g of iron?

[Relative atomic mass: H = 1, O = 16, Fe = 56]

2.  Lithium hydroxide, LiOH is used to remove carbon dioxide from the exhaled air in the cabin
of a spaceship. [Relative atomic mass: H = 1, Li = 7, C = 12, O = 16]

2LiOH + CO2 → Li2CO3 + H2O

An outer space mission is carried out for a period of 18 days involving five people on board. If
each person is expected to exhale on the average of 42 g of carbon dioxide per hour and each
absorption tube can contain 750 g of LiOH, calculate the number of absorption tubes that
should be loaded into the spaceship.

77

CHAPTER 3The Mole Concept, Chemical Formula and Equation
The Periodic
Table of
Elements

4

What will you learn?
4.1 The Development of the Periodic Table of Elements
4.2  The Arrangement in the Periodic Table of Elements
4.3 Elements in Group 18
4.4 Elements in Group 1
4.5 Elements in Group 17
4.6 Elements in Period 3
4.7 Transition Elements

CHAPTER

Periodic Table of
Elements

Groups
 Periods
 Noble gases
 Alkali metals
 Halogens
 Metalloids
 Transition elements

KeywordsKeywords

78
Who invented the Periodic Table
of Elements?

How are elements classified in the
Periodic Table of Elements?

What are the special characteristics
of transition elements?

Is the chlorine content in the swimming pool harmful to the health
of users? The answer is no. You need not worry because water
treated with chlorine only kills bacteria or dangerous organisms.
Users of the swimming pool do not get infected with contagious
diseases. In fact, you need not worry about the effects of accidentally
swallowing 100 cm3 of chlorinated water each day during your
swimming activity.

The strong smell in the swimming pool results from the reaction
of urea (from sweat) with chlorine. This reaction produces a
substance called trichloramine (nitrogen trichloride). This substance
may be harmful to health. Therefore, before entering the swimming
pool, it is advisable for you to clean yourself first so that the urea
due to sweat on the surface of the skin is removed.

Did you know that the characteristics of chlorine element can
be obtained by studying the position of chlorine in the Periodic Table
of Elements? This is because all the elements in the Periodic Table
of Elements are arranged systematically, therefore we are able to
know the characteristics of chlorine element.

Bulletin

79
The Development of the Periodic Table
of Elements

4.1

Lavoisier classified elements according to certain groups such
as gases, non-metals, metals and metal oxides. However, his
classification was less accurate because he also classified light,
heat and a few compounds into the groups as elements. Besides,
there were several elements that were classified into the same
group but showed different chemical properties.

Dobereiner found that the atomic mass of strontium atom, Sr
was similar to the average mass of calcium atom, Ca and barium
atom, Ba. These elements had the same chemical properties.
A similar condition occurred with chlorine, Cl, bromine, Br
and iodine, I. The group consisting of these three elements was
named triad. Dobereiner’s classification was limited to several
elements only. However, his classification showed the relationship
between the chemical properties of elements and atomic mass.

Antoine Lavoisier
(1743 – 1794)

Johann W. Dobereiner
(1780 – 1849)

Newlands arranged elements according to their increasing atomic
masses. He arranged seven elements in a row because he found that
the chemical and physical properties of the first element recurred
at every eighth element. He named the arrangement as the Law of
Octaves. The Law of Octaves had only been conformed by the first
17 elements. However, the recurrence in properties of the eighth
element showed the presence of periodic pattern in the properties
of elements.

John Newlands
(1837 – 1898)

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
4.1.1  Describe the historical

development of the
Periodic Table
of Elements

4.1.2  Deduce the basic principle
of arrangement of
elements in the Periodic
Table of Elements

The Periodic Table of Elements classifies known chemical
elements in a table according to certain characteristics. Many
theories were explained by scientists before the modern Periodic
Table of Elements was produced. What were those theories?
Do you know the scientists involved in the development of the
Periodic Table of Elements?

THEME 2 Fundamentals of Chemistry

80
Meyer plotted the graph of atomic volume against atomic mass
of elements. He found that the elements at equivalent positions
on the curve of the graph had similar chemical properties. For
example, referring to the alkali metals such as lithium, sodium,
potassium and rubidium that were located at the peaks of the
curve. Meyer also proved the recurrence in properties of elements
similar to Newlands.

Mendeleev arranged the elements according to their increasing
atomic masses. Only elements with similar chemical properties
were arranged in the same vertical columns. He had left several
empty spaces in his periodic table to be filled by elements, yet
to be discovered. He was successful in predicting the properties
of undiscovered elements based on the properties of elements
located above and below an element in the table.

Lothar Meyer
(1830 – 1895)

Dmitri Mendeleev
(1834 – 1907)

Moseley studied the frequencies of X-ray released by various elements
and eventually found a relationship between the X-ray spectrum and
proton numbers. He proposed that each element ought to have its
own proton number. Then, he arranged the elements in the Periodic
Table of Elements according to their increasing proton numbers.
Moseley also left empty spaces in his periodic table like Mendeleev
and successfully predicted four elements, namely technetium, Tc,
promethium, Pm, hafnium, Hf and rhenium, Re which were
discovered later.

Henry Moseley
(1887 – 1915)

Basic Principle of Arrangement of Elements in the Periodic Table of Elements

Elements in the Periodic Table of Elements are arranged in
ascending order of proton numbers, ranging from 1 to 118.
Elements with similar chemical properties are placed in the same
vertical columns.
  Several new elements which were discovered such as
nihonium, Nh, moscovium, Mc, tennessine, Ts and oganesson, Og
were added into Period 7 of the Periodic Table of Elements.

Figure 4.1 The new elements

New elements discovered
are named after the location
or the name of the scientist.

TeaserBrain
From the historical
development of the Periodic
Table of Elements learned,
predict the basic principle
in the arrangement of
the elements.

TeaserBrain

CHAPTER 4The Periodic Table of Elements

81
Activity 4.1
CT

Yourself
TestTest

4.1

The Arrangement in the
Periodic Table of Elements

4.2

You have learned the
positions of metals,
non-metals and noble
gases in the Periodic Table
of Elements in Form 1.

Ti spLiteracy

Discussing the importance of classifying the elements

1. Carry out the Think-Pair-Share activity.
 2.  Scan the QR code on the right on the development of the Periodic

Table of Elements and think of the importance of classifying
the elements.

3. Discuss with your partner.
 4. Share your outcomes in front of the class.

1. Name the scientists that made the following discoveries:
  (a)  Classified elements into four groups according to their chemical properties, that is

gases, non-metals, metals and metal oxides
  (b) Proposed the Law of Octaves
  (c)  Constructed the triad groups consisting of three elements with similar

chemical properties

2.  In the historical development of the Periodic Table of Elements, Moseley arranged the
elements in ascending order of proton numbers. However, before the modern Periodic Table
of Elements was used, scientists made their own discoveries. Compare how Dobereiner and
Newlands arranged the elements in the Periodic Table of Elements before Moseley.

The modern Periodic Table of Elements is a form of systematic
classification of elements in ascending order of proton numbers
from left to right and from top to bottom. The arrangement of
elements is discussed from the aspects of groups, periods, proton
number and electron arrangement.

The vertical columns in the Periodic Table of Elements
are called Groups. There are 18 groups in the Periodic Table of
Elements. The number of valence electrons will determine the
position of the group of an element. Figure 4.2 shows the position of
the group of an element based on the number of valence electrons.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
4.2.1	 	Describe	briefly	the

modern Periodic Table
of Elements

4.2.2  Generalise the
relationship between the
proton number and the
position of elements in
the Periodic Table
of Elements

Century
Skills21st

Development of the
Periodic Table
of Elements

http://bit.ly/
35Sgp0A

THEME 2 Fundamentals of Chemistry

82
Element

with one or two
valence electrons

Group =  Number of valence
electrons

with three until eight
valence electrons

Group =  Number of valence
electrons + 10

Figure 4.2 Position of the group of an element

The horizontal rows in the Periodic Table of Elements are called Periods. There are seven
periods in the Periodic Table of Elements. The number of shells filled with electrons will determine
the position of an element in a period.

Table 4.1 explains the relationship between the proton number and the position of an element
in the Periodic Table of Elements based on the aspects of groups and periods.

Table 4.1 Relationship between the proton number and the position of elements in the
 Periodic Table of Elements.

Element Proton
number

Electron
arrangement

Valence
electron Group

Number
of shells

filled with
electrons

Period

Lithium, Li 3 2.1 1 1 2 2
Calcium, Ca 20 2.8.8.2 2 2 4 4

Aluminium, Al 13 2.8.3 3 3 + 10 = 13 3 3
Silicon, Si 14 2.8.4 4 4 + 10 = 14 3 3

Nitrogen, N 7 2.5 5 5 + 10 = 15 2 2
Oxygen, O 8 2.6 6 6 + 10 = 16 2 2

Bromine, Br 35 2.8.18.7 7 7 + 10 = 17 4 4
Krypton, Kr 36 2.8.18.8 8 8 + 10 = 18 4 4

Activity 4.2
CTPredicting the group and period of an element based on its

electron arrangement

1. Carry out the Round Table activity.
 2. Choose a representative to speak out the proton number of an element.
 3.  Group members take turns to note down the electron arrangement, group and period of that

element on a piece of paper.
 4. Discuss the correct answer.
 5.  Pin up your outcomes on the class notice board as a reference for other groups.

Century
Skills21st

CHAPTER 4The Periodic Table of Elements

83
Yourself
TestTest

4.2

Figure 4.3 Positions of Group 18 elements in
the Periodic Table of Elements

Activity 4.3
Relating the inert nature with the stability of duplet and octet electron

arrangements of Group 18 elements

1. Carry out this activity in groups.

Helium
Neon

Argon

Duplet

He Ne Ar

Octet

Figure 4.4

Elements in Group 184.3

He

Ne

Ar

Kr

Xe

Rn

Og

1. Write the symbols for magnesium, copper and fluorine.
 2.  State the electron arrangement and group, for each of the following elements. Refer the

Data Table of Elements on page 276 to get the proton number of each element.
  (a) Potassium, K (c) Chlorine, Cl
  (b) Carbon, C (d) Argon, Ar
 3. Draw the electron arrangements of lithium, Li and carbon, C.

Group 18 consists of elements of helium, He, neon, Ne, argon, Ar,
krypton, Kr, xenon, Xe, radon, Rn and oganesson, Og. Elements
in Group 18 are known as noble gases or inert gases. Activity 4.3
shows the relationship between the inert nature and the stability of
the electron arrangement in an element.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
4.3.1  Relate the inert

nature of Group 18
elements	to	its	stability

4.3.2  Generalise the changes
in	physical	properties
of elements when going
down Group 18

4.3.3	 	Describe	briefly	the
uses of Group 18
elements	in	daily	life

More information on
inert properties of neon

http://bit.ly/33zc7cm

THEME 2 Fundamentals of Chemistry

84
2.  Based on Figure 4.4, discuss the relationship between the inert nature of Group 18 elements and
the stability of electron arrangement in an element.

3. Present your findings in front of the class.

Noble gases are chemically unreactive due to valence shells
that are fully filled with electrons. Noble gases have achieved a
stable duplet or octet electron arrangement, causing the atoms of
noble gases to not donate, accept nor share electrons with the atoms
of other elements. The atoms of noble gases exist as monoatoms.

Changes in Physical Properties of Elements When Going Down Group 18

Going down Group 18, the size of atomic radius increases due to the increase in the number of
electrons and electron filled shells.

Table 4.2 Physical properties of Group 18 elements

Element Atomic radius (nm) Melting point (°C) Boiling point (°C) Density (g cm–3)

Helium, He 0.050 –270 –269 0.00017

Neon, Ne 0.070 –248 –246 0.00080

Argon, Ar 0.094 –189 –186 0.00170

Krypton, Kr 0.109 –156 –152 0.00350

Xenon, Xe 0.130 –122 –108 0.00550

Radon, Rn – –71 –62 –

Activity 4.4

TeaserBrain

TeaserBrain

Try to relate the increase in
the density of the elements
with the atomic mass
and atomic size of each
element, when going down
the group.

ChemistryChemistry

Noble gas is also known as
inert gas.

Going down the group, the melting point and boiling point
of the elements increase. Increase in the atomic size of elements
will increase the attraction force between the atoms. Therefore,
the attraction force becomes stronger and more heat energy is
required to overcome this force.

Constructing a model to compare the physical properties and changes in the

physical properties of Group 18 elements

1.  Carry out the Three Stray One Stay activity.
 2.  Construct a 2D or 3D model to compare the physical properties of at least two elements in

Group 18.
 3. Prepare an exhibition corner in class and display the models from each group.
 4.  Choose a representative to give explanations on the comparison and changes in the physical

properties of the selected Group 18 elements. The rest of the members will move around to seek
information from other groups on their selected Group 18 elements.

Century
Skills21st

CHAPTER 4The Periodic Table of Elements

85
Uses of Group 18 Elements in Daily Life

Activity 4.5

Figure 4.5 Uses of Group 18 elements

•	 Used	to	fill	weather	balloons
•	 Used	in	the	oxygen	tanks	of	diversHelium

•	 Used	to	fill	in	electric	bulbs
•	 Used	to	provide	an	inert	atmosphere	for	welding	in

high temperature
Argon

•	 Used	in	advertising	board	lightsNeon

•	 Used	in	flashlight	of	cameras
•	 Used	in	lasers	for	eye	retina	treatmentKrypton

•	 Used	in	lighthouse	lamps
•	 Used	for	anesthesia	Xenon

•	 Used	to	treat	cancer	Radon

You	have	identified	the	list	of	elements	found	in	Group	18	and	studied
the	changes	in	the	physical	properties	of	the	elements	as	you	go	down
the	group.	Did	you	know	that	Group	18	elements	have	many	uses	in
our	daily	life?

Summarising the uses of Group 18 elements in daily life

1. Carry out this activity in groups.
 2.  Watch a video clip on the uses of Group 18 elements in our

daily lives by searching the Internet or visiting the link given.
 3.  Based on the video, discuss with your group members and

summarise the uses of Group 18 elements in graphic form.
 4. Present your group work in front of the class.

Group 18 elements

http://bit.ly/2Be9EIw

THEME 2 Fundamentals of Chemistry

86
Photograph 4.1 shows the uses of several Group 1 elements. What other uses of these
elements that you know?

Lithium, Li is used in
battery	production.

Sodium, Na is used in
sodium vapour lamps.

Photograph 4.1 Uses of Group 1 elements

Potassium, K is used
in fertilisers.

Yourself
TestTest

4.3

Elements in Group 14.4

Li

Na

K

Rb

Cs

Fr

Figure 4.6 Positions of Group 1 elements in
 the Periodic Table of Elements

1. State the electron arrangement of helium, He.
 2. What is the type of electron arrangement of argon atom, Ar?
 3. Explain why neon, Ne does not react with other elements.
 4. Compare the boiling point of helium and argon. Explain.

Group 1 is made up of lithium, Li, sodium, Na, potassium, K,
rubidium, Rb, caesium, Cs and francium, Fr. Group 1 elements are
also known as alkali metals.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
4.4.1  Generalise the changes

in	physical	properties
of elements when going
down Group 1

4.4.2  Investigate through
experiment the chemical
properties of Group 1
elements with:

•	 Water
	 •	 Oxygen	gas
	 •	 Chlorine
4.4.3  Generalise the changes in

the	reactivity	of	elements
when going down Group 1

4.4.4	 	Reason	out	the	physical
and chemical properties of
the other elements
in Group 1

CHAPTER 4The Periodic Table of Elements

87
Changes in Physical Properties of Elements When Going Down Group 1

Going down Group 1, the atomic radius of elements increases as shown in Table 4.3.

Table 4.3 Physical properties of several Group 1 elements

Element Atomic radius (nm) Melting point (°C) Boiling point (°C)

Lithium, Li 0.133 186 1342

Sodium, Na 0.186 98 880

Potassium, K 0.203 64 760

Group 1 elements have low melting point and boiling point if compared to other metals like
iron that has a melting point of 1 540 °C and boiling point of 2 760 °C. Why do the melting point
and boiling point of elements decrease when going down the group? The increase in the atomic size
down the group will weaken the attraction force between the atoms. Therefore, less heat energy is
required to overcome the attraction forces between the metal atoms.

Group 1 elements are soft metals, with low density and float on the surface of water. These
alkali metals also have a grey shiny surface at room temperature.

Chemical Properties of Group 1 Elements

Group 1 elements have one electron in the valence shell. In a chemical reaction, these atoms donate
one electron and form an ion with the +1 charge.

M → M+ + e–

What will happen when Group 1 elements react with water, oxygen gas or chlorine gas?

Experiment 4.1

Aim: To study the chemical properties of Group 1 elements.
Problem statement:  What are the chemical properties of Group 1 elements, when they react with

water, oxygen gas and chlorine gas?
Materials:  Lithium, sodium, potassium, distilled water, filter paper, red litmus paper, oxygen and

chlorine gas
Apparatus:  Forceps, white tile, basin, knife, combustion spoon, gas jar with lid, 10 cm3 measuring

cylinder and Bunsen burner

Reaction of Group 1 elements with water (Demonstration by the teacher)

Hypothesis:  Going down the group, the reactivity of alkali metals with water will increase.
Variables:

(a) Manipulated : Type of alkali metal
(b) Responding : Reactivity of alkali metal with water
(c) Fixed : Size of alkali metal

Be careful when putting the
alkali metal into the water.
Only small quantities should
be used.

Safety Precaution

THEME 2 Fundamentals of Chemistry

88
Procedure:

1. Cut lithium into small pieces using a knife and forceps. Dry a piece of the metal on a filter paper.
 2. Put the piece of lithium slowly into a basin filled with water as shown in Figure 4.7.

Lithium, Li
Basin

Distilled water

3. When the reaction is complete, test the solution with a red litmus paper.
 4. Record your observations in Table 4.4.
 5. Repeat steps 1 to 4 with sodium and potassium.

Reaction of Group 1 elements with oxygen gas

Make a hypothesis and state all the variables for part B.

Procedure:

1.  Cut lithium into small pieces using a knife and forceps.
Dry a piece of the metal on a filter paper.

2. Put the piece of lithium onto a combustion spoon.
 3.  Heat until it starts to burn and immediately insert the

spoon into a gas jar filled with oxygen gas as shown
in Figure 4.8.

4.  When the reaction is complete, add 10 cm3 of water
into the gas jar and shake.

5. Test the solution using a red litmus paper.
 6. Record your observations in Table 4.4.
 7. Repeat steps 1 to 6 with sodium and potassium.

Reaction of Group 1 elements with chlorine gas

Make a hypothesis and state all the variables for part C.

Procedure:

1. Cut lithium into small pieces using a knife and forceps. Dry a piece of the metal on a filter paper.
 2. Put the piece of lithium onto a combustion spoon.
 3.  Heat until it starts to burn and immediately insert the spoon into a gas jar filled with chlorine gas

as shown in Figure 4.8.
 4. Record your observations in Table 4.4.
 5. Repeat steps 1 to 4 with sodium and potassium.

Figure 4.8

Gas jar

Combustion spoon

Oxygen, O2

Lithium, Li

Figure 4.7

CHAPTER 4The Periodic Table of Elements

89
Results:

Table 4.4

Metal
Observation

With water With oxygen gas With chlorine gas

Lithium

Sodium

Potassium

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?
Discussion:

1. Write the chemical equation for the reaction of lithium, sodium and potassium with:
  (a) Water
  (b) Oxygen gas
  (c) Chlorine gas
 2. Arrange the reactivity of alkali metals lithium, sodium and potassium with water, oxygen gas

and chlorine gas in ascending order.

Reaction of Group 1 Elements with Water, Oxygen Gas and Chlorine Gas

Lithium, sodium and potassium have the same chemical properties
but different reactivity.

When alkali metals react with water, alkaline hydroxide solution
and hydrogen gas is formed. For example, reaction of lithium with
water will produce lithium hydroxide and hydrogen gas.

2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)

When alkali metals burn in oxygen gas, a white solid that is metal oxide will be formed.
For example, reaction of lithium with oxygen gas will produce lithium oxide.

4Li(s) + O2(g) → 2Li2O(s)

Solid metal oxide will form an alkaline solution when dissolved in water. For example,
reaction of lithium oxide with water will produce lithium hydroxide.

Li2O(s) + H2O(l) → 2LiOH(aq)

When alkali metals burn in chlorine gas, a white solid, that is metal chloride will be formed.
For example, reaction of sodium with chlorine gas will produce sodium chloride.

2Na(s) + Cl2(g) → 2NaCl(s)

Prepare a complete report after carrying out this experiment.

EduwebTV:
Alkali metal

http://bit.ly/
31h4LZN

THEME 2 Fundamentals of Chemistry

90
Physical and Chemical Properties of Other Elements in Group 1

You have studied the properties of lithium, sodium and potassium.
How about the properties of other atoms such as rubidium,
caesium and francium?

Like other alkali metals, rubidium, caesium and francium
elements are soft metals with shiny surfaces and have low melting
point and boiling point. Rubidium and caesium are metals that are
very reactive and burn easily. Rubidium and caesium are usually
combined with other elements. Thus, they are difficult to be
isolated chemically. Francium element is an unstable radioactive
isotope with a short half-life. All three elements are very reactive
with water and oxygen.

Changes in Reactivity of Elements Going Down Group 1

Li

Na

K

Reactivity
increases

Lithium, Li

Sodium, Na

Potassium, K

Experiment 4.1 shows the reactivity
of elements increases when going
down Group 1. Why do the
changes occur?

The reactivity of alkali metals in
Group 1 is due to the tendency of an
atom to donate its valence electrons.
The number of shells filled with
electrons increases when going down
Group 1. This causes the increase in
atomic size.

The position of valence electrons
is placed further away from the
nucleus of an atom. When the nuclear
attraction force towards the valence
electrons weakens, the electrons are
more easily donated.

Lithium batteries like those
used in smartphones can
explode when charged
excessively because it
accepts current rapidly.
So, only original and
good quality chargers
should be used to charge
your devices.

Chemistry& Us

Figure 4.9 Reactivity of elements increases
when going down Group 1

Reactions of elements
in Group 1
with water

http://bit.ly/
2MhYybu

CHAPTER 4The Periodic Table of Elements

91
LearningLearning
StandardStandard

1. Give two examples of Group 1 elements.
 2. Table 4.5 shows the electron arrangement for elements X, Y and Z.

Table 4.5

Elements Electron arrangement
X 2.1
Y 2.8.8.1
Z 2.8.18.8.1

(a) Give two differences in physical properties between elements  X, Y and Z.

(b) Element X reacts with oxygen when heated. Write the chemical equation for
this reaction.

(c) Arrange the reactivity of elements X, Y and Z in ascending order. Explain the difference
in reactivity.

Figure 4.10 Position of Group 17 elements in
the Periodic Table of Elements

Elements in Group 174.5

F

Cl

Br

I

At

Ts

Group 17 consists of fluorine, F, chlorine, Cl, bromine, Br,
iodine, I, astatine, At and tennessine, Ts. Group 17 elements
are known as halogens and exist as diatomic molecules.

At the end of the lesson,
pupils are able to:
4.5.1 Generalise the changes in

the physical properties of
elements when going
down Group 17

4.5.2 Summarise the chemical
properties of Group 17
elements

4.5.3 Generalise the changes in
the reactivity of elements
when going down

Group 17
4.5.4 Reason out the physical

and chemical properties of
other elements in Group 17

Do you know the uses of Group 17 elements in our daily lives? Photograph 4.2 shows the
examples of daily uses for elements chlorine, bromine and iodine.

Yourself
TestTest

4.4

THEME 2 Fundamentals of Chemistry

92
Changes in Physical Properties of Elements When Going Down Group 17

Going down Group 17, the physical state of halogens at room temperature changes from gas to
liquid and finally to solid as shown in Table 4.6.

Table 4.6 Physical properties of several Group 17 elements

Element Physical state Melting point (°C) Boiling point (°C) Density (g cm–3)

Chlorine, Cl Gas –101 –34 0.00300

Bromine, Br Liquid –7 59 3.11900

Iodine, I Solid 114 184 4.95000

Going down the group, the increase in molecular size will cause the attraction force between
molecules to become stronger. The melting point and boiling point of halogens will increase
because more heat energy is required to overcome the intermolecular forces. The density of
elements also increases with the increase in mass when going down the group.

Group 17 elements have different colours. Chlorine gas is greenish yellow, liquid bromine is
reddish brown while solid iodine is purplish black.

Chemical Properties of Group 17 Elements

Group 17 elements have seven electrons in the valence shell. In chemical reactions, these atoms
receive one electron and form ions with –1 charge.

X + e– → X–

What will happen if Group 17 elements react with water, metals or alkalis?

Photograph 4.2 Uses of Group 17 elements

Chlorine	in	bleach	 Iodine as a disinfectant Bromine as a substance
in	fire	extinguishers

BLEACH

CHAPTER 4The Periodic Table of Elements

93
THEME 2 Fundamentals of Chemistry

Reaction of Group 17 Elements with Water, Metal and Alkali

Chlorine, bromine and iodine have the same chemical properties
but different reactivity.

When halogens react with water, an acidic solution is
formed. For example, the reaction of chlorine with water will
produce hydrochloric acid and hypochlorous acid.

Cl2(g) + H2O(l)  HCl(aq) + HOCl(aq)

When halogens react with metal, a metal halide is formed.
For example, the reaction of iron with bromine will produce
iron(III) bromide.

2Fe(s) + 3Br2(l) → 2FeBr3(s)

Watching the reactions of Group 17 elements

1. Carry out the activity in groups.
 2. Based on Internet search, watch the video clips on the reactions of Group 17 elements with

water, metal and alkali.

Reaction of halogen
with water

http://bit.ly/2ILzLdZ

Reaction of halogen
with iron, Fe

http://bit.ly/2VJzpcR

Reaction of halogen
with sodium
hydroxide, NaOH

http://bit.ly/32kGWS4

3. Based on the videos above, discuss the following questions:
  (a)  Write chemical equations for the reactions of chlorine with water, iron and

sodium hydroxide.
  (b) Arrange the reactivity of chlorine, bromine and iodine with iron in ascending order.
  (c) Halogens are reactive non-metal elements. Explain.

When halogens react with an alkaline solution, metal halide, metal halate and water will
be formed. For example, the reaction of iodine with sodium hydroxide will produce sodium
iodide, sodium iodate(I) and water.

I2(s) + 2NaOH(aq) → NaI(aq) + NaOI(aq) + H2O(l)

Activity 4.6

Antoine Balard discovered
hypochlorous acid when he
added a dilute suspension
of mercury(II) oxide into a
flask filled with chlorine gas.

Century
Skills21st

94
CHAPTER 4The Periodic Table of Elements

Figure 4.11 Reactivity of elements decreases
when going down Group 17

Reactivity
decreases

Chlorine, Cl

Bromine, Br

Iodine, I

Watching the safety precautions in handling Group 17 elements

1. Carry out the activity in groups.
 2. Watch the video clip on safety precautions on handling

Group 17 elements by surfing the Internet.
 3. Based on the video, carry out a forum titled ‘Safety

Precautions in Handling Group 17 Elements’. Discuss the
following questions:
(a) Group 17 elements are dangerous. Explain.
(b) What are the safety precautions taken when handling

halogens like chlorine and bromine in the laboratory?

Changes in Reactivity of Elements Down Group 17

Physical and Chemical Properties of Other Elements in Group 17

Based on what you have learned, can you predict the physical and chemical properties of fluorine
and astatine? Generally, all halogens are soluble in organic solvents and do not conduct heat nor
electricity. Fluorine is a light-yellow poisonous gas. This gas which is very reactive and corrosive
will cause a strong explosion when combined with hydrogen gas. Astatine is a rare radioactive
element because it is not chemically stable.

Did you know that the reactivity
of elements decreases when going
down Group 17? Increasing
atomic size will cause the
valence shell to be further from
the nucleus. This will cause the
nuclear attraction force towards
the electrons to become weaker.
Thus, the difficulty in attracting
electrons to fill the valence shell
will increase.

Cl

Br

I

Be careful when handling
Group 17 elements because
they are dangerous.

Activity 4.7

Example on safety
measures in
handling halogens

http://bit.ly/33vshDO

95
THEME 2 Fundamentals of Chemistry

LearningLearning
StandardStandard

Yourself
TestTest

4.5

Magnesium, Mg
as a substance in
a lighter

Sulphur, S as
fungicides

Phosphorus, P
as a substance in
fireworks

Aluminium, Al as
a substance in cans

Period 3 consists of elements sodium, Na, magnesium, Mg,
aluminium, Al, silicon, Si, phosphorus, P, sulphur, S, chlorine, Cl,
and argon, Ar.

Figure 4.12 Position of Period 3 elements in the Periodic Table of Elements

You have learned about the uses of sodium, Na, chlorine, Cl, and argon, Ar. The uses of
several other elements in Period 3 are shown in Photograph 4.3.

Photograph 4.3 Uses of Period 3 elements

1. State three physical properties of elements down the Group 17.
 2. Fluorine is very reactive compared to iodine. The reaction of fluorine with almost all other

elements is very vigorous. Why is fluorine more reactive compared to iodine?
 3. Give two examples of substances that contain Group 17 elements.
 4. Astatine is not used in the science laboratory. Explain.

Elements in Period 3 4.6

ArClSPSiAlMgNa

At the end of the lesson,
pupils are able to:
4.6.1 Describe the trends in

physical properties of
elements across Period 3

4.6.2 Conduct an experiment
to observe changes in
the properties of the
oxides of elements
across Period 3

4.6.3	 Describe	briefly	the	uses
of semi-metals

96
CHAPTER 4The Periodic Table of Elements

Changes in Physical Properties of Elements Across Period 3

Going across Period 3 from left to right, the atomic size will decrease because the atomic
radius decreases.

Table 4.7 Physical properties of Period 3 elements

Atomic size decreases

Elements Sodium,
Na

Magnesium,
Mg

Aluminium,
Al

Silicon,
Si

Phosphorus,
P

Sulphur,
S

Chlorine,
Cl

Argon,
Ar

Atomic radius (nm) 0.186 0.160 0.143 0.118 0.110 0.104 0.100 0.094
Electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 –
Physical state Solid Gas

Increase in the number of protons across Period 3 will increase the charge in the atom̕s
nucleus. The electronegativity of elements will increase because the nuclear attraction force
towards the electrons increases.

The physical state of Period 3 elements will change from solid to gas from left to right across the
period. The same goes to metal elements, semi-metal elements and non-metal elements. Sodium, Na,
magnesium, Mg and aluminium, Al are metal elements, silicon, Si is a semi-metal element or
metalloid while phosphorus, P,  sulphur, S, chlorine, Cl and argon, Ar are non-metal elements.

Changes in Chemical Properties of Oxides of Elements Across Period 3

You have learned the properties of metal elements, semi-metal elements and non-metal elements
in Period 3. How about the chemical properties of oxides of elements across Period 3?

Experiment 4.2

Aim: To study the change of chemical properties of oxides of elements across Period 3.
Problem statement: How does the chemical properties of oxides of elements change across Period 3?
Materials: Sodium oxide, Na2O, magnesium oxide, MgO, aluminium oxide, Al2O3 sulphur

dioxide gas, SO2, silicon(IV) oxide, SiO2, distilled water, 2.0 mol dm–3 sodium
hydroxide, NaOH and 2.0 mol dm–3 nitric acid, HNO3

Apparatus: Test tube, stopper, test tube holder, 10 cm3  measuring cylinder, pH meter, Bunsen
burner, glass rod and spatula

Reaction of oxides of Period 3 elements with water

Hypothesis: Across Period 3, oxides of elements will change from basic to acidic.
Variables:

(a) Manipulated : Type of oxide of Period 3 elements
(b) Responding : Change in oxide property
(c) Fixed : Volume of water
Procedure:

1. Pour 10 cm3 distilled water into a test tube containing half spatula of sodium oxide, Na2O
and shake.

2. Measure the pH value of the solution in the test tube using a pH meter.
97
THEME 2 Fundamentals of Chemistry

3. Record your observations.
 4. Repeat steps 1 to 3 using magnesium oxide, MgO, aluminium oxide, Al2O3 and sulphur

dioxide, SO2.
Results:

Table 4.8

Oxide Sodium oxide,
Na2O

Magnesium oxide,
MgO

Aluminium oxide,
Al2O3

Sulphur dioxide,
SO2

With water

pH value

Reaction of oxides of Period 3 elements with sodium hydroxide and nitric acid

Make hypothesis and state all the variables for part B.
Procedure:

1. Fill
1
4 spatula of magnesium oxide powder, MgO

into two different test tubes.
 2. Add 5 cm3 of 2.0 mol dm–3 sodium hydroxide

solution, NaOH into the first test tube.
 3. Add 5 cm3 of 2.0 mol dm–3 nitric acid, HNO3 into

the second test tube.

4. Heat both test tubes gently and stir using a glass rod as shown in Figure 4.13.
 5. Observe the solubility of oxide in both solutions and record your observations.
 6. Repeat steps 1 to 5 by using aluminium oxide Al2O3 and silicon(IV) oxide, SiO2.
Results:

Table 4.9

Oxide
Solubility

With sodium hydroxide, NaOH With nitric acid, HNO3

Magnesium oxide, MgO

Aluminium oxide, Al2O3

Silicon(IV) oxide, SiO2

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?
Discussion:

1. List the basic oxides, amphoteric oxides and acidic oxides.
 2. Write the chemical equation for the reaction between basic oxide and nitric acid, HNO3.
 3. Write the chemical equation for the reaction between amphoteric oxide and sodium

hydroxide, NaOH.
 4. List the elements that have basic oxides and acidic oxides across Period 3.

Figure 4.13
Heat

Nitric acid,
HNO3

Sodium
hydroxide,
NaOH

Magnesium
oxide, MgO

Heat

Prepare a complete report after carrying out this experiment.

98
CHAPTER 4The Periodic Table of Elements

Going across Period 3, the properties of oxide change from basic oxide to amphoteric oxide
and then to acidic oxide.

Na2O MgO Al2O3 SiO2 P4O10 SO2 Cl2O7

Basic oxide Amphoteric oxide Acidic oxide

Figure 4.14 Properties of oxides of elements across Period 3

Group 1 and 2 elements form metal oxides that are basic. When dissolved in water, both basic
oxides will produce alkaline solutions. Basic oxides also react with acid to form salt and water.

Aluminium forms metal oxide that is amphoteric in property. Aluminium oxide reacts with
both acid and alkali to form salt and water.

Elements from Groups 14, 15, 16 and 17 form non-metal oxides that are acidic in property.
When dissolved in water, oxides of elements from these groups will produce acidic solutions.
Acidic oxides will also react with alkali to form salt and water.

You have learned the change of physical and chemical properties of elements across Period 3.
Can you predict the change of properties for elements across Period 2?

Uses of Semi-Metallic Elements

Semi-metallic elements or metalloid have both the properties of metals and non-metals. These
elements are weak conductors of electricity. However, metalloids are good electrical conductors
at high temperatures. Based on that property, metalloids like silicon are used as semiconductors
in the manufacture of electronic microchips. Photograph 4.4 shows the uses of electronic
microchips in the production of computers and mobile phones.

Computer

Mobile phone

Photograph 4.4 Electronic microchips used in the making of computers and mobile phones

Activity 4.8
Predicting the change of properties for elements in Period 2

1. Carry out the Round Table activity.
 2. Based on the change of properties of elements across Period 3, discuss and predict the change

of properties for elements across Period 2.
 3. Take turns to record the information on a piece of paper.
 4. Pin up the outcome of your group discussion on the class bulletin board as a reference to others.

Century
Skills21st

99
THEME 2 Fundamentals of Chemistry

Activity 4.9
Discussing the uses of semi-metals in the microelectronic industry

1. Carry out the Gallery Walk activity.
 2. Collect information from reading materials or suitable websites on the uses of the following

semi-metals in the microelectronic industry.

3. Discuss among your group members and prepare a presentation.
 4. Display your group work in the class. Move around in groups to see the work of other groups.
 5. Write comments on their work and paste them.

Yourself
TestTest

4.6

1. Why are the elements sodium, Na, magnesium, Mg, aluminium, Al, silicon, Si, phosphorus, P,
sulphur, S, chlorine, Cl and argon, Ar in the same period?

2. Silicon exists as a solid at room temperature while non-metals like chlorine exists as a gas.
Explain.

3. Figure 4.15 shows several elements in the Periodic Table of Elements.

Cl

NeC

AlNa

Figure 4.15
(a) When aluminium and chlorine are compared, which element has a smaller atomic size?

Explain.

(b) Which element forms an amphoteric oxide?
(c) Arrange all the elements in accending order of atomic size.

Century
Skills21st

100
CHAPTER 4The Periodic Table of Elements

LearningLearning
StandardStandardPosition of Transition Elements

Transition elements are placed in Group 3 and 12 in the Periodic
Table of Elements. Examples of transition elements include
chromium, Cr, manganese, Mn, iron, Fe, and copper, Cu. The
yellow portion in Figure 4.16 shows the position of transition
elements in the Periodic Table of Elements.

Transition Elements 4.7

Figure 4.16 Position of transition elements in the Periodic Table of Elements

1
1

H
3

Li
4

Be
11

Na
12

Mg
19

K
20

Ca
37

Rb
38

Sr
55

Cs
56

Ba
87

Fr
88

Ra

57 – 71

Lanthanides

89 – 103

Actinides

21

Sc
22

Ti
39

Y
40

Zr
72

Hf
104

Rf

23

V
24

Cr
41

Nb
42

Mo
73

Ta
74

W
105

Db
106

Sg

25

Mn
26

Fe
43

Tc
44

Ru
75

Re
76

Os
107

Bh
108

Hs

27

Co
28

Ni
45

Rh
46

Pd
77

Ir
78

Pt
109

Mt
110

Ds

29

Cu
30

Zn
47

Ag
48

Cd
79

Au
80

Hg
111

Rg
112

Cn

31

Ga
32

Ge
49

In
50

Sn
81

Tl
82

Pb
113

Nh
114

Fl

33

As
34

Se
51

Sb
52

Te
83

Bi
84

Po
115

Mc
116

Lv

35

Br
36

Kr

13

Al
14

Si
15

P
16

S
17

Cl
18

Ar

5

B
6

C
7

N
8

O
9

F
10

Ne

2

He

53

I
54

Xe

57

La
58

Ce
89

Ac
90

Th

59

Pr
60

Nd
91

Pa
92

U

61

Pm
62

Sm
93

Np
94

Pu

63

Eu
64

Gd
95

Am
96

Cm

65

Tb
66

Dy
97

Bk
98

Cf

67

Ho
68

Er
99

Es
100

Fm

69

Tm
70

Yb
101

Md
102

No

71

Lu
103

Lr

85

At
86

Rn
117

Ts
118

Og

18

2

3 4 5 6 7 8 9 10 11 12

13 14 15 16 17

All transition elements are metals with the following
properties:

•	 Solids	with	shiny	surfaces
•	 Very	hard	compared	to	metals	in	Groups	1	and	2
•	Have	high	densities
•	Have	high	melting	points	and	boiling	points

Special Characteristics for Several Transition Elements in the Periodic Table

of Elements

Transition elements are metals with high melting point and boiling point, hard, shiny surfaces,
malleable and ductile. Transition elements also have special characteristics unknown to other
metals. What are the special characteristics possessed by transition elements?

Transition elements function as a catalyst to increase the rate of reaction without
undergoing chemical change at the end of the reaction. For example, iron filings are used
as a catalyst in the Haber Process.

N2(g) + 3H2(g)
200 − 300 atm
450 − 550 oC, Fe

2NH3(g)

1

At the end of the lesson,
pupils are able to:
4.7.1 Determine the position of

transition elements in the
Periodic Table of Elements

4.7.2 Explain the special
characteristics of a few
transition elements
with examples

4.7.3 List the uses of transition
elements in industry

ChemistryChemistry

Scandium and zinc are not
considered as transition
elements because both do
not show characteristics of
transition elements.

Position of transition
elements

http://bit.ly/
2B8OlYG

101
THEME 2 Fundamentals of Chemistry

Table 4.11

Transition
element

Oxidation
number Compound

Chromium, Cr +3
+6

Chromium(III) chloride, CrCl3
Potassium dichromate(VI), K2Cr2O7

Mangan, Mn
+2
+4
+7

Manganese(II) chloride, MnCl2
Manganese(IV) oxide, MnO2
Potassium manganate(VII), KMnO4

Iron, Fe +2
+3

Iron(II) sulphate, FeSO4
Iron(III) chloride, FeCl3

Copper, Cu +1
+2

Copper(I) oxide, Cu2O
Copper(II) oxide, CuO

Table 4.10

Transition element ions Colour of solution

Chromium(III) ion, Cr3+(aq)
Dichromate(VI) ion, Cr2O7

2–(aq)
Green

Orange

Manganese(II) ion, Mn2+(aq)
Manganate(VII) ion, MnO4

–(aq)
Pink

Purple

Iron(II) ion, Fe2+(aq)
Iron(III) ion, Fe3+(aq)

Green
Brown

Copper(II) ion, Cu2+(aq) Blue

Activity 4.10
Observing the colour of the transition element compounds

1. Observe the colour of the following transition element compounds:
(a) Chromium(IIl) chloride, CrCl3 (f) Iron(II) sulphate, FeSO4

(b) Potassium dichromate(Vl), K2Cr2O7 (g) Iron(III) chloride, FeCl3

(c) Manganese(II) chloride, MnCl2 (h) Copper(I) oxide, Cu2O
(d) Manganese(IV) oxide, MnO2 (i) Copper(II) oxide, CuO
(e) Potassium manganate(VII), KMnO4

2. Present your findings in the form of a suitable mind map to share with your friends.

Transition elements form coloured
ions or compounds.

2

Transition elements
have more than one
oxidation number.

3

Photograph 4.5 Coloured compounds of
transition elements

EduwebTV: Transition
elements

http://bit.ly/2BcvM5Z

102
CHAPTER 4The Periodic Table of Elements

Table 4.12

Ion of transition element Formula

Tetraaminecopper(II) ion [Cu(NH3)4]
2+

Hexacyanoferrate(III) ion [Fe(CN)6]
3–

Hexacyanoferrate(II) ion [Fe(CN)6]
4–

Hexaaquaferrate(II) ion [Fe(H2O)6]
2+

Uses of Transition Elements in Industry

One of the special characteristics of transition elements is their use as a catalyst in industries.
Do you know which transition elements are involved in that function? Figure 4.17 shows the
examples of transition elements that function as a catalyst in industries.

Activity 4.11
Conducting the learning activity based on the problems related to

the special characteristics of transition elements

1. Carry out the activity in groups.
 2. Read and understand the following passage:

Scientists found a special characteristic of certain transition elements that can ̒remember̕
their form. For example, an alloy called Nitinol is a mixture of nickel and titanium that
can return to its original form after the alloy is bent. This alloy is used in making spectacle
frames and treating broken bones.

3. Gather information on problems that can be solved using transition elements and their
special characteristics.

4. Justify the use of transition elements and relate them to their special characteristics.
 5. Prepare a multimedia presentation based on your findings.
 6. Present your group work in front of the class.

Transition elements can form
complex ions.

4

Figure 4.17 Transition elements as catalysts in industries

Vanadium(V) oxide, V2O5 is used
in the Contact Process to produce
sulphuric acid, H2SO4.

Transition
Elements

Iron, Fe is used in the Haber
Process to produce ammonia, NH3.

Platinum, Pt is used in the Ostwald
Process to produce nitric acid, HNO3.

Nickel, Ni or platinum, Pt is used
in the hydrogenation process on
vegetable oils to produce margarine.

CTCentury
Skills21st

103
THEME 2 Fundamentals of Chemistry

Activity 4.12

Yourself
TestTest

4.7

1. Table 4.13 shows three transition elements that exist in gems.
Table 4.13

Gem Transition element
Ruby Chromium

Sapphire Iron, titanium
Amethyst Manganese

(a) What are the special characteristics of the transition elements shown in Table 4.13?

(b) Apart from the characteristics given in 1(a), what are the other characteristics found in
transition elements?

2. Give examples of several transition elements used in industry.

Iron is used to build bridges Titanium is used to
make paints

Photograph 4.6 Uses of transition elements

Manganese is used to make
stained glass windows

Apart from catalyst, other uses of transition elements are shown in Photograph 4.6.

Making a scrap book/ brochure/ pamphlet/ poster to show the uses of several

transition elements in various industries

1. Carry out this activity in groups.
 2. Gather information from various reading materials and search relevant websites for the use of

several transition elements in various industries.
 3. Discuss with your group members and present your findings in a scrap book/ brochure/

pamphlet/ poster.
 4. Exhibit the scrap book/ brochure/ pamphlet/ poster in the laboratory or class.

104
CHAPTER 4The Periodic Table of Elements

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105
THEME 2 Fundamentals of Chemistry

Self Reflection

1. What new knowledge have you learned in The Periodic Table of Elements?
 2. Which is the most interesting subtopic in The Periodic Table of Elements? Why?
 3. Give a few examples of elements in The Periodic Table of Elements that you use in your

daily life.
 4. Rate your performance in The Periodic Table of Elements on

a scale of 1 to 10; 1 being the lowest and 10 the highest. Why
would you rate yourself at that level?

5. What else would you like to know about The Periodic Table
  of Elements?

http://bit.ly/
31kIQk8

Achievement 4

1. How did Moseley arrange the elements in the Periodic Table of Elements?

2. Figure 1 shows the chemical symbol for element X.
(a) Which group does element X belong to in the Periodic Table of Elements?
(b) Which period does element X belong to in the Periodic Table of Elements?

3. A restaurant owner uses colourful electric lights to attract his customers. What is the
substance suitable for making such lights?

4. State the physical and chemical properties of the element with electron arrangement 2.8.8.1.

5. State the element in Period 3 that forms an amphoteric oxide.

6. Figure 2 shows several elements in the Periodic Table of Elements that are represented by
alphabets X and Y.

X

Y

Figure 2

(a) Write the electron arrangement for atom X and atom Y.
(b) Explain two differences in chemical properties between element X and element Y.

(c) Why does the reactivity of elements in the same group as X, increase when going down
the group, but the reactivity of elements in the same group as Y decreases?

35 X
17
Figure 1

106
CHAPTER 4The Periodic Table of Elements

7. Chlorine, Cl2 reacts with sodium, Na to form a compound. Write the chemical equation for
the reaction.

8. Figure 3 shows the electron arrangement for the element G.
(a) Which group does element G belong to in the

Periodic Table of Elements?
(b) Which period does element G belong to in the

Periodic Table of Elements?
(c) State a physical property of element G.

9.
Na

Mg

Al

Si

P

S

Cl

Ar

(a) State which element is a metal, metalloid or non-metal from the list of elements
given above.

(b) Explain the change in atomic radius across the Period from left to right.
(c) Which element is a noble gas?
(d) Write the chemical equation when a metal reacts with water.

10. Give the colour of the following transition element ions:
(a) Iron(II) ion
(b) Iron(III) ion

Check   AnswersAnswers

https://bit.ly/
2pHzJ04

Figure 3

G

CornerEnrichmen
 1. Photograph 1 shows a few microchips. Silicon element is widely used in the manufacture

industries of microchips.

Photograph 1 Microchips

What is the property of silicon that enables this element to be used in the manufacture of
microchips instead of a metal like lithium? Explain.

107
Teflon

Chemical
Bond5

What will you learn?
5.1	 Basics	of	Compound	Formation
5.2	 Ionic	Bond
5.3	 Covalent	Bond
5.4	 Hydrogen	Bond
5.5	 Dative	Bond
5.6	 Metallic	Bond
5.7	 Properties	of	Ionic	Compounds	and

Covalent	Compounds

Chemical bonds
 Ionic bonds
 Electrostatic
attraction force

Covalent bonds
 Hydrogen bonds
 Dative bonds
 Van der Waals
attraction force

KeywordsKeywords

CHAPTER

108
What	is	meant	by	chemical	bond?

Why	is	ethanol	soluble	in	water?

How	are	dative	bonds	formed?

Dato' Dr. Sheikh Muszaphar Shukor is the first Malaysian
astronaut sent to the outer space. During his stay in the
outer space, he needs to wear an astronaut suit.

The astronaut suit is created specifically to protect
the astronaut’s body from the space environment.
Did you know that the astronaut suit is made up of five
layers? The layers consist of an inner layer of cotton,
followed by a layer of blue nylon, a layer of black nylon,
Teflon layer and lastly white nylon on the outer side.
All layers of nylon and Teflon are macromolecules made
from covalent compounds by covalent bonds, a type of
chemical bond that is very strong.

Bulletin

109
Basics of Compound Formation5.1

Sodium, Na is reactive towards chlorine gas, Cl2 when heated and
forms a white solid. Did you know that this white solid is the
table salt that you use in your daily life? However, no compound
is formed when sodium, Na is heated with neon gas, Ne. Why?

Compounds are formed when two or more elements are
combined. Do you know how elements are combined to produce compounds?

Watching a video on the formation of compounds

1. Carry out the activity in groups.
 2. Watch video clips on the formation of compounds

by electron transfer (ionic bonds) and by sharing of
electrons (covalent bonds) from your Internet search.

3. Based on those videos, discuss the following:
(a) Formation of compounds by transfer of electrons to

achieve a stable octet or duplet electron arrangement
(b) Formation of compounds by sharing of electrons to

achieve a stable octet or duplet electron arrangement
 4. Present the findings of your discussion on a flip chart paper in front of the class.

Noble gases exist as monoatomic gases and are not reactive
chemically because they have achieved a stable duplet or octet
electron arrangement. However, for atoms of other elements,
stability of electron arrangement can be achieved by transferring
or sharing of electrons. Chemical bonds are formed when electron
transfer or electron sharing takes place. There are two types of
chemical bonds; ionic bond and covalent bond. Chemical bonds
only involve the valence electrons.

TeaserBrain

TeaserBrain

Why are electrons in the
inner shells not involved in
chemical bonds?

Activity 5.1

Figure 5.1 Formation of ionic bond

Are you sure?
Thank you.

Yes, I am very
positive about it.

I only have seven electrons in
the valence shell. I need one
more electron to achieve an
octet electron arrangement.

Cl Cl ClNa Na Na

There! I have one
extra electron.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
5.1.1 Explain the basics of

compound formation

Ionic bond

http://bit.ly/2MfCmit

Covalent bond

http://bit.ly/2BeDXi1

110

THEME 2 Fundamentals of Chemistry
1. What is chemical bond?
 2. State two types of chemical bonds.
 3. Why noble gases do not form compounds?
 4. Is the electron arrangement of sodium atom, Na stable? If not, explain how the electron

arrangement can become stable.

I have only
one electron.

Let us share
our electrons.I also have

one electron.
Wow! We have achieved
duplet electron arrangement.

Ionic Bond5.2

Yourself
TestTest

5.1

H HH H
Figure 5.2 Formation of covalent bond

Situation in Figure 5.3 gives the analogy for the formation of ionic
bond. Ionic bond is formed by the transfer of electrons between a
metal atom and a non-metal atom.

There is still space in my
egg container because I
have only seven eggs.

Thank you, Siti. Now
both the containers
are fully filled.

Kana, I have nine eggs
but this egg container can
only hold eight eggs.

In that case, let me
give you an egg.

Figure 5.3 Analogy for the formation of ionic bond

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
5.2.1 Explain with examples

the formation of
ionic bond

111

Chemical Bond CHAPTER 5
Half-equation for the formation of sodium ion, Na+:
Na  Na+ + e–

Half-equation for the formation of fluoride ion, F–:
F + e–  F–

Formation of Ions

Metal atom donates valence electron to form a positively-charged ion or cation. Figure 5.4 shows
the formation of sodium ion, Na+.

To achieve a stable electron arrangement, sodium
atom, Na needs to donate an electron. The process
of donating an electron from the valence shell
of sodium atom, Na is much easier compared to
accepting seven electrons from another atom.

To achieve a stable electron arrangement, fluorine
atom, F will accept an electron. The process of
accepting one electron to the valence shell of
fluorine atom, F is easier compared to donating its
seven valence electrons to another atom.

After donating its valence electron, sodium ion,
Na+ achieves a stable octet electron arrangement.
Sodium ion, Na+ has 11 protons and 10
electrons, thus the charge for a sodium ion, Na+
is +1.

After receiving one valence electron, fluoride ion,
F– achieves a stable octet electron arrangement.
Fluoride ion, F– has 9 protons and 10 electrons,
so the charge of fluoride ion, F– is –1.

2.8.1
Sodium atom, Na

2.7
Fluorine atom, F

2.8
Sodium ion, Na+

2.8
Fluoride ion, F–

Figure 5.4 Formation of sodium ion, Na+

Non-metal atom receives electron from a metal atom to form a negatively-charged ion or
anion. Figure 5.5 shows the formation of fluoride ion, F–.

Figure 5.5 Formation of fluoride ion, F–

Donates one electron

Accepts one electron

+

–

NaNa

F F

112

THEME 2 Fundamentals of Chemistry
Activity 5.2

2.8.1
Sodium atom, Na

2.7
Fluorine atom, F

2.8
Sodium ion, Na+

2.8
Fluoride ion, F–

Formation of Ionic Bond

An ionic compound is formed when ions of opposite charges attract one another to form an ionic
bond. How do ions of opposite charges attract one another?

Discussing the formation of ionic bonds

1. Carry out the Gallery Walk activity.
 2. Gather information from various reading resources and websites on the formation
  of ionic bonds for the following compounds:

Magnesium oxide, MgO

Sodium chloride, NaCl  Sodium oxide, Na2O

3. Scan the AR code to see the formation of ionic compound of sodium chloride, NaCl.
 4. Discuss the formation of ionic bonds with your group members and prepare a presentation.

You need to write half-equations for the formation of ions in each compound.
 5. Display your group work in class. Move around to see the outcome of other groups' discussion.
 6. Write comments on their work on sticky notes and paste them.

Figure 5.6 Formation of sodium fluoride, NaF

+

–+

Na NaF F

Sodium ion, Na+ and fluoride ion, F– of opposite charges will attract one another by strong
electrostatic attraction force. Electrostatic attraction forces are known as ionic bonds. A compound
sodium fluoride, NaF is formed.

Fluorine atom, F will accept
one electron from sodium
atom, Na to achieve a stable
octet electron arrangement.
Fluoride ion, F– is formed.

Sodium atom, Na will donate
one electron to achieve a stable
octet electron arrangement.
Sodium ion, Na+ is formed.

CT

113

Chemical Bond CHAPTER 5

Besides calcium carbonate, CaCO3,
sodium fluoride, NaF is also added to
toothpaste to strengthen the teeth.

Chemistry& Us

Century
Skills21st
Uji

Kendiri 1. Aluminium atom, Al has 13 protons while fluorine atom, F has 9 protons.
(a) Write the formulae of ions formed from the two atoms respectively.
(b) Write half-equations for the formation of ions in (a).

(c) Draw the electron arrangement to show the transfer of electrons in the formation of
ionic bonds in aluminium fluoride compound.

2. Muriate of Potash is a type of fertiliser that has a high content of potassium chloride
compound. [Proton number: Cl = 17, K = 19]
(a) Write the chemical formula for potassium chloride.
(b) Describe the formation of ionic bonds in potassium chloride compound.

Covalent Bond 5.3

Did you know that diamond is one of the hardest substances in
the world? The property of diamond is caused by the formation
of covalent bonds between carbon atoms.

Covalent bonds are formed when non-metal atoms
share their electrons to achieve a stable duplet or octet electron
arrangement. There are three types of covalent bonds; single
bond, double bond and triple bond.

Single Bond

A single bond is formed when two atoms share a pair of electrons.

Yourself
TestTest

5.2

Figure 5.7 Formation of single bond in chlorine molecule, Cl2

2.8.7
Chlorine atom, Cl Chlorine molecule, Cl2

2.8.7
Chlorine atom, Cl

2.8.82.8.8

Chlorine atom, Cl needs one
electron to achieve a stable octet
electron arrangement.

Two chlorine atoms, Cl each contributes one
electron to share a pair of electrons to form a
single bond in a chlorine molecule, Cl2.

+Cl Cl Cl Cl

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
5.3.1 Explain with examples

the formation of
covalent bond

5.3.2 Compare ionic bond and
covalent bond

114

THEME 2 Fundamentals of Chemistry
The formation of covalent bond can be visualised using the
Lewis structure. Lewis structure only shows the valence electrons
of the atoms involved. A pair of electrons shared, is represented
with a line between the two atoms.

+Cl Cl or Cl ClCl Cl
Figure 5.8 Lewis structure for the formation of chlorine molecule, Cl2

Double Bond

A double bond is formed when two atoms share two pairs
of electrons.

+

+

+N N or N NN N

2.6
Oxygen atom, O

2.5
Nitrogen atom, N

2.6
Oxygen atom, O

2.5
Nitrogen atom, N

2.8 2.8
Nitrogen molecule, N2

2.8     2.8
Oxygen molecule, O2or

or

+O O or O OO O

Figure 5.10 Formation of triple bond in nitrogen molecule, N2

Figure 5.9 Formation of double bond in oxygen molecule, O2

Triple Bond

A triple bond is formed when two atoms share three pairs of electrons.

O O O O

N N N N

ChemistryChemistry

Diamond consists of
carbon atoms, C. Each
carbon atom, C forms four
covalent bonds with another
four carbon atoms.

Oxygen atom, O needs two
electrons to achieve a stable
octet electron arrangement.

The nitrogen atom, N needs three
electrons to achieve a stable octet
electron arrangement.

Two oxygen atoms, O each contributes two
electrons to share two pairs of electrons to
form a double bond in oxygen molecule, O2.

Two nitrogen atoms, N each contributes three
electrons to share three pairs of electrons to
form a triple bond in nitrogen molecule, N2.

115

Chemical Bond CHAPTER 5
Activity 5.3
Visualising the formation of covalent bonds

1. Carry out the Three Stray One Stay activity.
 2. Build a model to visualise the formation of covalent bonds in the following compounds.

Hydrogen, H2

Hydrogen chloride, HCl

Oxygen, O2

Carbon dioxide, CO2

Nitrogen, N2

3. Prepare an exhibition corner in the class and display the models from each group.
 4. Choose a representative to give an explanation on the formation of covalent bond in a chosen

compound. The rest of the members will move around to seek information from
other groups.

Comparison between Ionic Bond and Covalent Bond

Similarities and differences between ionic bond and covalent bond are shown in Figure 5.11.

Figure 5.11 Comparison between ionic bond and covalent bond

Ionic
bond

Covalent
bond

CT

Between metal
atoms and
non-metal

atoms

Transfer of
electrons

Forms a
positively-

charged ion and
a negatively-
charged ion

Involve valence
electrons

only

Atoms achieve
stable octet or
duplet electron

arrangement

Between
non-metal

atoms

Sharing of
electrons

Forms a
molecules

Century
Skills21st

116

THEME 2 Fundamentals of Chemistry
1. State three types of covalent bonds.
 2. How are covalent bonds formed?
 3. Draw the formation of covalent bonds in a water molecule, H2O.

4. Can carbon atoms, C share electrons with four hydrogen atoms, H to form a methane
molecule? Explain. [Proton number: H = 1, C = 6]

5. State one similarity and two differences between ionic bond and covalent bond.

Yourself
TestTest

5.3

Hydrogen Bond5.4

Figure 5.12 Formation of hydrogen bonds between water molecules, H2O

H H

H

H

O

O

Have you ever thought why an iceberg weighing thousands
of tonnes is able to float on the surface of the sea? This is
because the density of ice is lower compared with water. Why is
water denser than ice? To answer this question, the concept of
hydrogen bonds needs to be understood.

Hydrogen bonds are attraction forces between hydrogen
atom, H that has bonded with an atom of high electronegativity,
such as nitrogen, N, oxygen, O or fluorine, F with nitrogen,
N, oxygen, O or fluorine, F in another molecule. For example,
water molecule, H2O can form hydrogen bonds among water
molecules, H2O.

Water molecule, H2O consists of
two hydrogen atoms, H and one
oxygen atom, O. Hydrogen, H and
oxygen, O are bonded by sharing
electrons with one another. This
type of bond is a covalent bond.

Attraction forces between
hydrogen atom, H in water
molecule with oxygen atom, O
from another water molecule
forms a hydrogen bond.

LearningLearning
StandardStandard

At the end of the lesson,
pupils should be able to:
5.4.1 Explain with examples

the formation of a
hydrogen bond

5.4.2 Explain the effect of
the hydrogen bond on
physical properties

of substances

Oxygen atom, O has
high electronegativity.

117

Chemical Bond CHAPTER 5
Activity 5.4
Discussing the formation of hydrogen bonds in hydrogen

fluoride, HF and ammonia, NH
3

1. Carry out the Think-Pair-Share activity.
 2. Based on Figure 5.12, think about how hydrogen bonds are formed in hydrogen fluoride, HF

and ammonia, NH3.
 3. Discuss with your partner.
 4. Share your findings in front of the class.

Cellulose in paper
consists of hydrogen
atoms, H that are bonded
to oxygen atoms, O.

Water molecules, H2O on
the wet finger will form
hydrogen bonds with the
cellulose in paper. Because
of that, paper will stick to
the finger.

Figure 5.15 Hydrogen bonds formed between cellulose in paper and water molecule, H2O on the finger
Paper cellulose

H
H H

H
H H

H
H

O
O O

O

O

O

CT

Role of Hydrogen Bonds in Daily Life

Observe Figure 5.13. There are protein molecules that form hydrogen bonds among one another
in the hair structure. Do you know why hair sticks together when wet?

Figure 5.13 Hydrogen bonds between protein molecules in the hair structure

When hair is wet, protein molecules no longer form
hydrogen bonds among themselves. Instead, protein molecules
will form hydrogen bonds with water molecules, H2O. Water
molecules, H2O will also form hydrogen bonds with other hair
protein molecules. This causes hair to stick together.

Have you ever come across the problem of turning the
pages of a book where the pages stick together? To overcome
this problem, you lick your finger before turning the pages.
Why does a wet finger help to turn the pages of a book?
Explanation on this is given in Figure 5.15.

Hair

TeaserBrain

TeaserBrain

Why does wavy hair look
straight when wet?

Figure 5.14
Formation of hydrogen bond
between protein molecule and

water molecule

Protein molecules

Hydrogen bonds

H
H
O O

H
H
O O

H
H
O O

Hydrogen bonds

H
H

H
HO OO

Century
Skills21st

118

THEME 2 Fundamentals of Chemistry
H C C

H H H

H H

O

H

O

H
O

H

HH C C

H H

H H

O

H

1. State the meaning of hydrogen bond.
 2. Hydrogen fluoride, HF exists as liquid at room temperature. Explain this phenomenon

based on the formation of hydrogen bonds.
 3. Can hydrogen bonds form among hydrogen chloride molecules, HCl?
  Justify your answer.

4. Explain why paper sticks together when wet.

Effect of Hydrogen Bonds on The Physical Properties of Substances

Compounds in the form of liquids reach boiling point when the attraction forces between molecules
are overcomed. In the covalent compound of ethanol, C2H5OH, there are hydrogen bonds formed
between molecules, other than weak Van der Waals attraction forces. Strong hydrogen bonds are
difficult to break. More heat energy is required to overcome the weak Van der Waals attraction
forces, besides breaking the hydrogen bonds. As a result, the boiling point of ethanol, C2H5OH
is high. On the other hand, molecules like chlorine, Cl2 which do not form hydrogen bonds have
lower boiling point compared to ethanol.

Ethanol, C2H5OH is also soluble in water. The solubility of ethanol, C2H5OH in water is due to
the formation of hydrogen bonds between the ethanol molecule, C2H5OH and water molecule, H2O.

Yourself
TestTest

5.4

Ethanol molecule, C2H5OH

Figure 5.16 Solubility of ethanol, C2H5OH in water, H2O

Ethanol, C2H5OH consists
of hydrogen atoms, H that
form covalent bonds with
oxygen atoms, O. So, the
oxygen atom, O in ethanol
molecule, C2H5OH can
form a hydrogen bond
with the hydrogen atom, H
from water molecule, H2O.

The hydrogen
atom, H in ethanol
molecule, C2H5OH
can also form a
hydrogen bond
with the oxygen
atom, O from water
molecule, H2O.

Van der Waals
attraction force

Activity 5.5
Discussing the solubility in water and boiling point of

covalent compounds

1. Carry out the Round Table activity.
 2. Gather information on the solubility in water and boiling point for hydrogen fluoride, HF and

ammonia, NH3 from various reading materials and websites.
 3. Compare the solubility and boiling point for these compounds with molecules that do not form

hydrogen bonds.
 4. Take turns to record the related information on a piece of paper.
 5. Pin up your group work on the classroom bulletin board to share the information and

references with other groups.

CTCentury
Skills21st

119

Chemical Bond CHAPTER 5
Activity 5.6
Discussing the formation of dative bond in ammonium ion, NH

4

+

1. Carry out this activity in groups.
 2. Based on the statement below, discuss the formation of dative

bonds in ammonium ion, NH4
+.

When hydrogen chloride gas, HCl and ammonia gas, NH3
are mixed, white fumes of ammonium chloride, NH4Cl is
formed as shown in Photograph 5.1.

3. Present your discussion results in an attractive presentation
in front of the class.

Figure 5.17 Formation of dative bond

Dative bond or coordinate bond is a type of covalent bond where the electron pair that is shared
comes from one atom only. How does such sharing take place? Figure 5.18 shows the formation of
dative bond in hydroxonium ion, H3O

+.

I do not
have electrons.

I have a pair
of electrons to
be shared.

I am still in octet
electron arrangement.

Dative Bond5.5

H+ H+NH3 NH3

+

+H
OH

H
OH HH+

In hydroxonium ion, H3O
+,

oxygen atom, O and
all hydrogen atoms, H
have achieved stable
octet and duplet electron
arrangements respectively.

Hydrogen ion, H+ does not have
any electron in the shell.

Oxygen atom, O achieves
octet electron arrangement
and hydrogen atom, H
achieves stable duplet
electron arrangement in
water molecule, H2O.

Figure 5.18 Formation of dative bond in hydroxonium ion, H3O
+

1

2
4

The lone pair of electrons that are not involved in covalent bond
in water molecule, H2O will be shared with hydrogen ion, H+
through the formation of dative bond.

3

Photograph 5.1
Formation of white fumes of
ammonium chloride, NH4Cl

Hydrochloric ac
id

Ammonia

Wow! I have
achieved duplet
electron arrangement.

LearningLearning
StandardStandard

At the end of the lesson,
pupils should be able to:
5.5.1 Explain with examples the

formation of dative bond

120

THEME 2 Fundamentals of Chemistry
1. What is dative bond?
 2. Explain the formation of ammonium ion through the formation of dative bond between

hydrogen ion, H+ and nitrogen atom, N in ammonia, NH3.

3. Boron atom, B found in the compound boron trifluoride, BF3 has not achieved octet
electron arrangement because it has only six valence electrons. Can boron atoms, B form
dative bonds with nitrogen atoms, N in the compound ammonia, NH3?

Explain your answer.

When electrons of metal atoms are
delocalised in the sea of electrons, the
metal can conduct electricity. Electrons that
move freely in the metal structure carry
the charges from the negative terminal to
the positive terminal when electricity is
supplied, as shown in Figure 5.20.

Yourself
TestTest

5.5

Metallic Bond5.6

Figure 5.20 Electrical conductivity of metals

Did you know that exposed electrical wires can cause electric
shock? Electrical wires made from metal can conduct electricity.
Why can metals conduct electricity?

Metal atoms are arranged closely packed and orderly in
the solid state. Valence electrons of metal atoms can be donated
easily and delocalised although in the solid state. Metal ions
that are positively-charged are formed when valence electrons
are delocalised. All delocalised valence electrons can move
freely between the metal structure and form a sea of electrons.
Electrostatic attraction force between the sea of electrons and the
positively-charged metal ions form the metallic bond.

+ + + + +

+ + + + +

+ + + + +

+ + + + +

Positive
terminal

Electron

+−

Metal

ChemistryChemistry

Delocalised electron
means electron that moves
freely and is not owned by
any atom nor ion. A sea of
electron is formed when
the valence shells of metal
atoms overlap, resulting in
electron delocalisation.

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +

+ + + + +
Sea of electron

Valence
electron

Positively-
charged
metal ions

Figure 5.19 Formation of metallic bond

LearningLearning
StandardStandard

At the end of the lesson,
pupils should be able to:
5.6.1 Explain the formation of

a metallic bond
5.6.2 Reason out the electrical

conductivity of metal

Negative
terminal

121

Chemical Bond CHAPTER 5
Activity 5.7

Comparing and contrasting the formation of bonds

1. Carry out the Think-Pair-Share activity.
 2. Using suitable mind maps, compare and contrast the formation of all bonds studied from the

following aspects:
(a) Sharing or transfer of electrons
(b) Attraction forces formed
(c) Examples of compounds or elements

3. Pin up your mind maps produced on the classroom bulletin board.

Yourself
TestTest

5.6

1. What is meant by a delocalised electron?
 2. How a metallic bond is formed in metals?
 3. Using aluminium, Al metal as an example, explain how metals can conduct electricity.

Properties of Ionic Compounds and
Covalent Compounds

5.7

Observe salt (sodium chloride, NaCl) and ice in Photograph 5.2.
Are both substances in the same physical state? Which substance
will melt at room temperature?

Salt is an ionic compound Ice is a covalent compound

Photograph 5.2 Example of ionic compound and covalent compound

Different compounds have different properties. The different properties of ionic compounds
and covalent compounds can be studied through Experiment 5.1.

CT

LearningLearning
StandardStandard

At the end of the lesson,
pupils should be able to:
5.7.1 Compare the

properties of ionic
compounds and
covalent compounds
through experiment

5.7.2 Explain with
examples the uses of
ionic compounds and
covalent compounds
in daily life

Century
Skills21st

122

THEME 2 Fundamentals of Chemistry
Experiment 5.1

Aim: To study the difference in properties between ionic compounds and covalent compounds.
Problem statement: What are the difference in properties between ionic compounds and
 covalent compounds?
Materials: Solid lead(Il) bromide, PbBr2, naphthalene, C10H8, magnesium chloride, MgCl2,

cyclohexane, C6H12 and distilled water
Apparatus: Test tubes, spatula, evaporating dish, Bunsen burner, pipeclay triangle, wire gauze,

beaker, 10 cm3 measuring cylinder, tripod stand, battery, switch, light bulb and
 carbon electrodes

A  Electrical conductivity of compounds

Hypothesis: Ionic compounds can conduct electricity in molten
state but not in the solid state while covalent
compounds cannot conduct electricity in both states.

Variables:

(a) Manipulated : Type of compound
(b) Responding : Electrical conductivity
(c) Fixed : Carbon electrode
Procedure:

1. Put lead(II) bromide, PbBr2 powder into the crucible
until half full.

2. Set up the apparatus as shown in Figure 5.21.
 3. Switch on and observe whether the bulb lights up.
 4. Switch off and heat the lead(II) bromide, PbBr2 powder

until all solids have melted.
 5. Switch on once again and observe whether the bulb

lights up.
 6. Repeat steps 1 to 5 using naphthalene, C10H8 powder.
 7. Record your observations on the condition of the bulb

in Table 5.1
Results:

Table 5.1

Carry out this experiment in
the fume chamber.

Carbon
electrodes

Bulb

Crucible

Lead(II)
bromide, PbBr2

Switch

Heat

Figure 5.21

• Naphthalene, C10H8 is a
flammable substance.

• Bromine gas, Br2 produced
during the heating of
lead(II) bromide, PbBr2
is poisonous.

Safety Precaution

Compound Physical state Condition of bulb

Lead(II) bromide, PbBr2

Solid

Molten

Naphthalene, C10H8

Solid

Molten

123

Chemical Bond CHAPTER 5

Excessive exposure to
naphthalene, C10H8 can cause
haemolytic anaemia, liver
and nervous system failure,
cataract and bleeding of
the retina.

Chemistry& Us
B  Solubility of compound in water and organic solvents

Make hypothesis and state all variables.
Procedure:

1. Put half spatula of magnesium chloride, MgCl2 powder
  into the test tube.
 2. Add 5 cm3 of distilled water into the test tube and

shake gently.
 3. Observe the solubility of magnesium chloride, MgCl2 in water.
 4. Repeat steps 1 to 3 using cyclohexane, C6H12 as the solvent.
 5. Repeat steps 1 to 4 and substitute magnesium chloride, MgCl2 with naphthalene, C10H8.
 6. Record your observations on the solubility of compounds in Table 5.2.
Results:

Table 5.2

Compounds Solubility in
distilled water

Solubility in
cyclohexane, C6H12

Magnesium chloride, MgCl2

Naphthalene, C10H8

C  Melting point and boiling point of compound

Make hypothesis and state all variables.
Procedure:

1. Put half spatula of magnesium chloride, MgCl2 powder and
naphthalene, C10H8 into separate test tubes.

2. Heat both test tubes in the water bath as shown
  in Figure 5.23.
 3. Observe and record the change in physical states and make
  inference of both substances in Table 5.3.

Results:

Table 5.3

Compound Observation Inference

Magnesium chloride, MgCl2

Naphthalene, C10H8

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?
Discussion:

1. What type of compound is lead(II) bromide, PbBr2, magnesium chloride, MgCl2 and
naphthalene, C10H8?

2. Predict the electrical conductivity, solubility, melting point and boiling point of sodium
chloride, NaCl.

Figure 5.22

Figure 5.23

Prepare a complete report after carrying out this experiment.

Magnesium
chloride,

MgCl2

Distilled
water

Cyclohexane,
C6H12

Magnesium
chloride,
MgCl2

Naphthalene,
C10H8

Distilled
water

Heat

124

THEME 2 Fundamentals of Chemistry
Electrical Conductivity

Based on Experiment 5.1, ionic compounds and covalent compounds have different electrical
conductivity. Ionic compounds cannot conduct electricity in the solid state but can conduct
electricity in the molten state and aqueous solution while covalent compounds cannot conduct
electricity in all states.

– +

+ – + – + – + – + – + –

+ – + – + – + – + – + –
+ – + – + – + – + – +–

Solid ionic
 compound

Solid or molten
covalent compound

– +

Ions can move freely
because electrostatic
attraction forces have been
overcomed. Molten or
aqueous solution of
ionic compound can
conduct electricity. Molten or aqueous

solution of ionic
compound

+

–
+

–

+ –+

–
+ –

+

–

+

–
+

–
+ – + –

+

–+ –
+

–

+ –+ – + –

+

–

+
–

– +

Molecules in covalent
compounds are neutral and do
not carry any charge. Therefore,
covalent compounds do not
conduct electricity in all states.

Ions cannot move freely
because they are tied by strong
electrostatic attraction forces.
Therefore, solid ionic compound
cannot conduct electricity.

Figure 5.24 Electrical conductivity of ionic compounds and covalent compounds

125

Chemical Bond CHAPTER 5
Solubility in Water and Organic Solvents

Most ionic compounds are soluble in water but are not soluble in
organic solvents. On the other hand, most covalent compounds
are not soluble in water but are soluble in organic solvents.

When dissolved in water, water molecules help to overcome
electrostatic attraction force between ions and break down the
lattice structure of the solid compound. As a result, ions can move
freely in water.

ChemistryChemistry

–
+

–
+

–
+

–
+

–
+

–
+

–
+

–
+

–
+ + +

+

–
+

–
+

–

–

–

–

–

–+ +

–
+

+

–
+

+

– +
+

–+ + –
+

+

–
+

+

–
+

+–
+

+

– ++ –
+

+

–
+

+

–+ +

–
+

+

–
+

+

– +
+

–
+

+

–
+

+ –
+

+
–

+
+

– +
+

–
+

+

–
+ + –

+
+

–+ +

–
+

+

– +
+

–+
+

–
+

+ – ++

+ +

δ+ δ+

δ–

The figure below shows the solubility of sodium chloride, NaCI in water. Water is a polar solvent that has
partial negative charge at the oxygen atom and partial positive charge at the hydrogen atom. Positive
ion, Na+ will be attracted to the oxygen atom of water molecule which is negatively-charged while negative
ion, Cl– will be attracted to the hydrogen atom of water molecule which is positively-charged.

Attraction force between atom of water molecules with the ions of ionic compound are strong
enough to overcome electrostatic attraction force between ions themselves. This enables most solid ionic
compounds to be soluble in water.

ChemistryChemistry

Lattice structure is the
orderly arrangement of
atoms, ions or molecules
of a compound in a
solid crystal.

Organic solvents cannot overcome electrostatic forces between ions in a solid ionic compound.
So, ionic compounds are not soluble in organic solvents. Molecules in a covalent compound are
neutral and do not carry any charges. So, molecules in a covalent compound are soluble in an
organic solvent but not soluble in water.

Melting Point and Boiling Point

You have learned that ionic compounds and covalent compounds are formed by ionic bonds and
covalent bonds respectively. Do you know that both the chemical bonds influence the melting
point and boiling point of a compound? Are these chemical bonds overcomed when compounds
are melted or boiled?

Solid sodium chloride, NaCl

Chloride ions, Cl− are
attracted to the positive
side of the water.

Water molecule, H2O

H H
O

Sodium ions, Na+  are
attracted to the negative
side of the water.

In a water molecule,
oxygen atom has a higher
electronegativity than
hydrogen atom.This causes
the electrons shared in the
covalent bond to be pulled
towards the oxygen atom.
The unequal sharing of
electrons creates partial
negative charge, δ− at the
oxygen atom and partial
positive charge, δ+ at the
hydrogen atom.

Ti spLiteracy

126

THEME 2 Fundamentals of Chemistry
An ionic compound like sodium chloride, NaCl
consists of positive ions, Na+ and negative ions, Cl–
that attract one another by strong electrostatic
attraction forces.

High heat energy is required to overcome the strong
electrostatic attraction forces so that the ionic compound
can melt or boil. Thus, sodium chloride, NaCl has a high
melting point and boiling point.

Figure 5.25 Ionic compounds have high melting point and boiling point

Covalent compounds with simple molecules have low melting point and boiling point.
Hence, covalent compounds with simple molecules are easily volatile.

Figure 5.26 Covalent compounds with simple molecules have low melting point and boiling point

Low heat energy is required to overcome the weak
Van der Waals attraction forces so that the covalent
compound can melt or boil. Thus, methane, CH4
has a low melting point and boiling point.

Van der Waals attraction forces
between simple molecules
in covalent compounds like
methane, CH4 are very weak.

++
– –

–

–
–

–

–
––

–

–
–

–
–

++
+

+

+
+

+

+
+

+
+

–Chloride ion, Cl–

Sodium chloride, NaCl

Sodium ion, Na+ +

Ionic compounds have high melting point and boiling point. Therefore, ionic compounds
are not easily volatile.

ChemistryChemistry

Lizards can stick to the surface of walls. This is due to the
reaction between some electrons from the molecules of
the hundreds of fine hairs found on the sole of the lizard’s
feet and some electrons from the molecules of the wall.
This reaction forms the electromagnetic attraction known
as Van der Waals attraction forces.

++
– –

–

–
–

–

–
––

–

–
–

–
–

++
+

+

+
+

+

+
+

+
+

–Chloride ion, Cl–

Sodium chloride, NaCl

Sodium ion, Na+ +

heated

HH

H

H

C HH

H

H

C

HH

H

H

C

Van der Waals
attraction

force
Methane molecule, CH4

127

Chemical Bond CHAPTER 5
Covalent bond

Silicon
atom, Si

Oxygen
atom, O

Silicon dioxide, SiO2

Water, H2O

Carbon dioxide, CO2

Figure 5.27 Difference between simple molecule and giant molecule in covalent compounds

Structure of Covalent Compounds

There are two types of molecular structure for covalent compounds which are simple molecular
structure and giant molecular structure. What is the difference between the simple molecular
structure and giant molecular structure in covalent compounds?

Covalent
compound

Small and simple
structures can be found in
the form of solids, liquids
or gases.

Covalent bonds are
strong in the molecules
and Van der Waals
attraction forces between
molecules are weak.

Low because only little
heat is required to
overcome the weak Van
der Waals attraction
forces between molecules.

Giant
molecule

Simple
molecule

Example

Very large structure,
usually exists as solids.

High because a lot
of heat is required
to break the strong
covalent bonds.

Strong covalent bonds in
the molecules only. No
Van der Waals attraction
forces between
molecules because of its
giant structure.

Chemical bond

Structure

Melting point and
boiling point

128

THEME 2 Fundamentals of Chemistry
Figure 5.28 Uses of ionic compounds and covalent compounds in our daily lives

Uses of Ionic Compounds and Covalent Compounds in Our Daily Lives

Most ionic compounds and covalent compounds used in our daily lives are in the industrial sector,
agriculture, medicine and domestic use.

Agricultural sectorIndustrial sector

Medical sector Domestic use

The uses of ionic compounds and
covalent compounds in daily life

The ionic compound
of lithium iodide, LiI
is used in batteries.

Paint contains
covalent compounds
such as pigment and
turpentine solvent.

The ionic compounds of
ammonium nitrate, NH4NO3
and potassium chloride, KCl
are used in fertilisers.

Pesticides used to kill weeds
and insects contain covalent
compounds such as
bromoethane, C2H5Br and
chloropicrin, CCl3NO2.

Sodium Bicarbonate

650 mg
100 Tablets

The ionic compound of
sodium bicarbonate, NaHCO3
is used in antacids to relieve
gastric pain.

Paracetamol, C8H9NO2
is a covalent compound
used to treat fevers and irritation.

GLYCEROL

Glycerol, C3H5(OH)3  is a covalent
compound added to skincare
products to moisturise skin and
help to prevent dry skin.

Detergents contain the
ionic compound, sodium
chlorate(V), NaClO3, which
is used for domestic cleaning.

129

Chemical Bond CHAPTER 5
Yourself
TestTest

5.7

1. Compare the melting point and boiling point of ionic compounds and covalent compounds.
 2. Give one similarity between simple molecule and giant molecule of covalent compounds.
 3. Magnesium hydroxide, Mg(OH)2 known as milk of magnesia, is a type of ionic compound

used to relieve gastric pain.
(a) State the solubility of magnesium hydroxide, Mg(OH)2 in water.
(b) Can magnesium hydroxide, Mg(OH)2 conduct electricity in the solid state?
(c) Explain your answer in 3(b).

4. Diamond is a giant molecule of covalent compound while methane, CH4 is a simple
molecule of covalent compound.
(a) Compare the melting point and boiling point of diamond and methane, CH4. Explain.

(b) Predict the electrical conductivity of diamond. Explain your prediction.

Activity 5.8

Carry out a problem-solving project on the use of ionic compounds

and covalent compounds in daily life

1. Carry out this activity in groups.
 2. Read and understand the following passage:

Plastic particles in the sea can cause problems to aquatic life ranging from plankton, fish to
big animals like turtles, dolphins and whales. The problem of aquatic life is not only the direct
intake of plastics but also the chemicals in the plastics that can be absorbed into the tissues of
these aquatic life.

3. Apart from the problem above, surf the Internet to find information about the problems of
using ionic compounds and covalent compounds in one of the following fields:
(a) Industry
(b) Agriculture
(c) Medicine
(d) Domestic

4. Discuss the ways to solve the problems.
 5. Present your findings in front of the class and carry out a question and answer session to

improve the proposals of each group.

CTCentury
Skills21st

130

THEME 2 Fundamentals of Chemistry
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131

Chemical Bond CHAPTER 5
Achievement 5

Self Reflection

1. What is the meaning of covalent bond?

2. Why does silicon dioxide, SiO2 have a high melting point and boiling point?

3. Figure 1 shows several elements in the Periodic Table of Elements that are represented by
letters A, D, E, G and H.

A

D E

HG

Figure 1

(a) State the elements that can combine to form ionic compounds.
(b) Element D reacts with element E to form a covalent compound. Write the chemical

formula of the covalent compound formed.

(c) Atoms of element H combine to form diatomic molecules at room temperature.
 Explain the melting point and boiling point of molecule H.

4. Figure 2 shows the chemical symbols for elements Q and R.
(a) Write the electron arrangement for atom Q and atom R.
(b) Element Q and element R react to form compound S.

(i) State the type of chemical bond formed.
(ii) Explain the process of formation of compound S.

1. What new knowledge have you learned in Chemical Bond?
 2. Which is the most interesting subtopic in Chemical Bond? Why?
 3. Give a few examples on the application of Chemical Bond in daily life.
 4. Rate your performance in Chemical Bond on a scale of 1 to 10;

1 being the lowest and 10 the highest. Why would you rate
yourself at that level?

5.  What else would you like to know about Chemical Bond?

http://bit.ly/
31le1ft

24
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8R

Figure 2

132

THEME 2 Fundamentals of Chemistry
5. •	 Atom	of	element	J has 12 neutrons and 23 nucleon number
•	 Atom	of	element	K has 9 protons

(a) Which element is a metal?
(b) Explain how element J combines with element K to form white solid T.

6. Element D combines with element E to form a covalent compound with chemical formula
ED3. Element D has a proton number of 17. Predict the electron arrangement of the atom of
element E with reasonable explanation.

7. Water, H2O exists as liquid while hydrogen chloride, HCl exists as gas at room temperature.
Explain this phenomenon based on the formation of hydrogen bonds.

8. Copper, Cu is a metal that is commonly used in the manufacturing of electric wires. Explain
briefly how this metal can conduct electricity.

9. Kevin found a beaker filled with white solid left on top of the table in a laboratory. He
would like to know what type of compound the white solid is. He carried out several tests to
investigate the physical properties of the white solid and obtained the following results:

•	 Soluble	in	water
•	 Can	conduct	electricity	in	liquid	state

Based on your observation and knowledge, predict the type of compound of this white solid.
Explain your prediction.

Figure 1

(a) (b)

Check   AnswersAnswers

https://bit.ly/
2PbIFFq

1. Deoxyribonucleic acid, DNA in organism is a complex
macromolecule that stores genetic information. DNA
consists of polynucleotides that coil around each
other to form the double helix structure as shown in
Figure 1(a). Based on the DNA structure as shown in
Figure 1(b), explain how polynucleotides coil around
each other using the concept of hydrogen bonds.

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133

Chemical Bond CHAPTER 5
What will you learn?
6.1	 The	Role	of	Water	in	Showing	Acidic	and	Alkaline	Properties
6.2 pH Value
6.3 Strength	of	Acids	and	Alkalis
6.4  Chemical	Properties	of	Acids	and	Alkalis
6.5 Concentration	of	Aqueous	Solution
6.6	 Standard	Solution
6.7	 Neutralisation
6.8 Salts,	Crystals	and	Their	Uses	in	Daily	Life
6.9 Preparation	of	Salts
6.10	 Effect	of	Heat	on	Salts
6.11	 Qualitative	Analysis

Acid, Base and
Salt6

Limestone	cave,
Taman Negara Mulu

CHAPTER

Basicity of acids
 pH and pOH
 Strength of acids and
alkalis

Molarity
 Standard solutions
 Neutralisation
 Titration
 Insoluble salts
 Recrystallisation
 Double decomposition
reactions

KeywordsKeywords

134
What	is	the	relationship	between	pH	value
and	concentration	of	hydrogen	ions,	H+?

Why	are	all	alkalis	bases	but	not	all
bases	are	alkalis?

How	does	a	laboratory	assistant	prepare	a
standard	solution?

Stalactites

Stalagmites

How are stalactites and stalagmites formed in
limestone caves? Limestone caves consist of calcium
carbonate, CaCO3. When rainwater falls on the caves
seep through the limestone, the following reaction
takes place to produce calcium bicarbonate
salt, Ca(HCO3)2.

H2O(l) + CO2(g) + CaCO3(s) → Ca(HCO3)2(aq)

The flowing water will carry the soluble calcium
bicarbonate, Ca(HCO3)2 through the crevices at
the roof of the caves. When the water comes in
contact with air in the caves, a small portion of
calcium bicarbonate, Ca(HCO3)2 reverts back to
calcium carbonate, CaCO3, due to water and carbon
dioxide losses. Calcium carbonate, CaCO3 starts to
precipitate on these crevices. Hence, the formation
of stalactites begins gradually. Water that drips from
the ends of the stalactites will fall on the floor of
the cave. Over the time, stalagmites will form in the
same way as stalactites. This is why stalactites and
stalagmites are found together in the caves.

Formation of stalactites
and stalagmites

http://bit.ly/2ISEfPQ

Bulletin

135
Figure 6.1 Acidic and alkaline substances in daily life
Acids

When acid is dissolved in water, the hydrogen atoms in acid
molecules are released in the form of hydrogen ions, H+. Therefore,
based on the Arrhenius theory, acid is defined as follows:

Chemical substances ionise in water to produce hydrogen
ions, H+.

HCl(aq) → H+(aq) + Cl–(aq) HNO3(aq) → H+(aq) + NO3
–(aq)

When hydrogen chloride gas is dissolved in water, hydrogen
chloride molecules will ionise in water to produce hydrogen ions,
H+ and chloride ions, Cl–. However, do the hydrogen ions, H+
remain in the aqueous solution? Literally, hydrogen ions, H+
produced will combine with the water molecules, H2O to form
hydroxonium ions, H3O

+.

+ +C1 C1–OH

H H

O+

H H

H

Figure 6.2 Formation of hydroxonium ion, H3O
+

The Role of Water in Showing Acidic and
Alkaline Properties

6.1

Dad, how can I make
this coin shiny again?

Mom, why do we
need to brush our
teeth every morning?Try scrubbing

it with lime.

In order to neutralise
the acid on our teeth.

ChemistryChemistry

Although hydroxonium ions,
H3O

+ are the actual ions
existing in the aqueous
solution that gives the
acidic properties, to simplify
explanation, we often use
hydrogen ion, H+ to represent
hydroxonium ions, H3O

+.

Situation in Figure 6.1 shows the uses of acidic and alkaline substances in daily life. Identify which
subtances are acidic and which substances are alkaline.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.1.1	 Define	acid	and	alkali
6.1.2 State the meaning of

basicity	of	an	acid
6.1.3 Investigate the role of

water	in	showing	acidic
and	alkaline	properties
through experiment

136

Interaction between MatterTHEME 3
Basicity of Acids

Basicity of acids refers to the number of hydrogen ions, H+ that can be produced by an acid
molecule that ionises in water. Hydrochloric acid, HCl is monoprotic acid because it can produce
one hydrogen ion, H+ per acid molecule. How about diprotic acid and triprotic acid?

Acids

Hydrochloric acid, HCl
produces one H+ ion

per acid molecule

Monoprotic acid

Sulphuric acid, H2SO4
produces two H+ ions

per acid molecule

Diprotic acid

Phosphoric acid, H3PO4
produces three H+ ions

per acid molecule

Triprotic acid

Figure 6.3 The classification of acids based on the basicity of the acids

Alkalis

Base is a substance that reacts with acids to produce salt and water only. Metal oxides and metal
hydroxides are bases. For example, magnesium oxide, MgO and calcium hydroxide, Ca(OH)2 are
bases because they react with acids to produce salt and water only.

MgO(s) + H2SO4(aq) → MgSO4(aq) + H2O(l)
  Salt

Ca(OH)2(aq) + 2HNO3(aq) → Ca(NO3)2(aq) + 2H2O(l)
  Salt

A base that is soluble in water is called an alkali. Potassium hydroxide, KOH and sodium
hydroxide, NaOH are alkalis because they are soluble in water. When sodium hydroxide pellets,
NaOH is dissolved in water, sodium ions, Na+ and hydroxide ions, OH– that can move freely in
water are produced.

Water
Na+ OH–

OH– Na+

Na+

OH–OH–

Na+

Figure 6.4 Dissociation of sodium hydroxide, NaOH into ions that move freely in water

Formic acid, HCOOH is used in the
coagulation of latex. Is formic acid, HCOOH
a diprotic acid? Why?

TeaserBrain

TeaserBrain

Observe the chemical equation below.
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Is magnesium a base? Why?

137

Acid, Base and Salt CHAPTER 6
Discussing the uses of acids and alkalis in daily life using

examples of acidic and alkaline substances

1. Carry out the activity in groups.
 2. Gather information from reading materials or websites on examples of acidic and alkaline

substances as well as their uses in various fields.

Agriculture Industries Medicine Food industry

An alkali is defined as follows:

Chemical substances that ionise in water to produce hydroxide ions, OH–.

What will happen to ammonia molecule when ammonia gas is dissolved in water? Why is
aqueous ammonia produced an alkali?

H + +N

O

H H

O–

H

H
H

N+

H

H

HH

Ammonia gas, NH3 Water, H2O Ammonium ion, NH4
+ Hydroxide ion, OH–

NH3(aq) + H2O(l)   NH4
+(aq) + OH–(aq)

Figure 6.5 Formation of hydroxide ion, OH– from ammonia molecule

By dissolving ammonia gas in water, aqueous ammonia is produced. Aqueous ammonia is an
alkali because the ammonia molecules ionise partially to produce hydroxide ions, OH–.

Uses of Acids, Bases and Alkalis

Acids, bases and alkalis are not just chemical
substances in the laboratory but they are also
widely found in daily life. Toothpaste which is
alkaline, functions to neutralise acid on the teeth,
while vinegar is an acidic substance used to make
pickled chillies.

Activity 6.1

Photograph 6.1 Uses of acid and alkali in
daily life

CT

ANTACID
TABLET

Century
Skills21st

138

Interaction between MatterTHEME 3
Experiment 6.1

3. Based on the information gathered, discuss the followings:
(a) Identify the acid, base or alkali in each substance that you have found
(b) State the use of acid, base or alkali found in the substance

4. Pin up your group work on the bulletin board to share the information and references with the
other groups.

Mom, why is the new
soap taken out of its
box not slippery?

It's slippery, mom!

Figure 6.6 Role of water to show alkalinity

Based on the conversation in Figure 6.6, why is the water added to the soap? Is water needed to
allow acids or alkalis to show acidic or alkaline properties?

Try to add some water
and rub the soap. What
do you feel now?

The Role of Water to Show Acidity and Alkalinity

137

Acid, Base and Salt CHAPTER 6

Aim: To study the role of water in showing acidic properties.
Problem statement: Is water needed to allow an acid to show its acidic properties?
Hypothesis: Water is needed for an acid to show its acidic properties.
Variables:

(a) Manipulated : Presence of water
(b) Responding : Colour change on blue litmus paper
(c) Fixed : Type of acid
Materials: Solid oxalic acid, C2H2O4, distilled water and blue litmus paper
Apparatus: Test tubes and test tube rack
Procedure:

1. Add a spatula of solid oxalic acid, C2H2O4 in a test tube.
 2. Insert a piece of dry blue litmus paper into the test tube.
Prepare a complete report after carrying out this experiment.

Acids only show acidic properties in the presence of water.
When an acid is dissolved in water, acid molecules will ionise to
produce hydrogen ions, H+. The presence of hydrogen ions H+
allows the acid to show its acidic properties. Therefore, blue litmus
paper changes to red. Without water, solid oxalic acid, C2H2O4
only exist as molecules. Hydrogen ions, H+ are not present. Thus,
the colour of blue litmus paper remains unchanged.

Reflect on the properties
of acid:

Sour taste
 Corrosive
 Has pH value less than 7
 Changes moist blue
litmus paper to red

Ti spLiteracy

3. Observe any changes to the colour of the blue litmus paper.
Record your observations.

4. After that, add 2 cm3 distilled water and shake well.
 5. Observe any changes to the colour of the blue litmus paper.

Record your observations.

Results:

Table 6.1

Contents Observations

Solid oxalic acid, C2H2O4

Solid oxalic acid, C2H2O4 + water

Interpreting data:

1. State the change in colour of the blue litmus paper that is used to detect acidic properties.
 2. Based on the observations, state a suitable inference.
 3. What are the conditions needed for an acid to show its acidic properties?

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Discussion:

1. Name the ion that is responsible for showing the acidic properties.
 2. Solid oxalic acid, C2H2O4 had differences in observation compared to the solid oxalic acid, C2H2O4

that has been dissolved in water. Give a reason.
 3. What is the operational definition for acid in this experiment?

Acid is corrosive. Be careful
when handling acid. If in
contact with acid, run
continuous flow of water
on the affected area.

140

Interaction between MatterTHEME 3
Experiment 6.2

Aim: To study the role of water in showing alkaline properties.
Problem statement: Is water needed to allow an alkali to show its alkaline properties?
Hypothesis: Make a suitable hypothesis for this experiment.
Variables: State all the variables involved in this experiment.

Figure 6.7 Method to test the alkaline properties of sodium hydroxide, NaOH

Procedure:

1. Based on Figure 6.7, list out the apparatus and materials required for this experiment.
 2. Plan the procedure for this experiment with your group members.
 3. Determine the method used to collect data and prepare a suitable table.
 4. Carry out the experiment with your teacher̕s permission.
 5. Record your observations in the table provided.

Results:

Record your observation in a table.

Interpreting data:

1. Based on the observations, state a suitable inference.
 2. What is the condition of the litmus paper needed to detect alkaline properties?

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Discussion:

1. Name the ion responsible to show alkaline properties.
 2. Explain the difference in observation between using a pellet of sodium hydroxide, NaOH and

sodium hydroxide solution, NaOH.
 3. Give the operational definition for alkali in this experiment.

Sodium hydroxide, NaOH is
corrosive. A pellet of sodium
hydroxide, NaOH is sufficient
to carry out this experiment.
If in contact with the alkaline
solution, run water over the
area continuously until it no
longer feels slippery.

Prepare a complete report after carrying out this experiment.

Sodium
hydroxide
pellet, NaOH Red litmus paper

Sodium hydroxide
solution, NaOH
produced

137

Acid, Base and Salt CHAPTER 6
Akalis only shows alkaline properties when they are dissolved
in water. Without water, hydroxide ions, OH– in the sodium
hydroxide pellet, NaOH cannot move freely and are still tied in its
lattice structure. So, the pellet of sodium hydroxide, NaOH does
not show alkaline properties. The red litmus paper cannot change
colour. When a pellet of sodium hydroxide, NaOH is dissolved in
water, hydroxide ions, OH– are produced and able to move freely
in water. Thus, sodium hydroxide solution, NaOH shows alkaline
properties. Hence, the moist red litmus paper turns blue.

The presence of water also enables ammonia gas, NH3 to ionise
and produce hydroxide ions, OH– that are responsible for its alkaline properties. Therefore, the
moist red litmus paper turns blue. Without water, ammonia gas, NH3 only exists as molecules.
Hydroxide ions, OH– are not present. So, red litmus paper remains unchanged.

Yourself
TestTest

6.1

1. State the meaning of the following terms:
(a) Acid
(b) Alkali

2. Carbonic acid is a mineral acid with the formula, H2CO3. What is the basicity of carbonic
acid? Explain why.

3. Figure 6.8 shows a conversation between Khairul and his teacher.

Khairul, what is
your problem? Teacher, the cleaning powder

is alkaline. Why doesn't the red
litmus paper turn blue?

(a) What possible mistake was committed by Khairul in his test?

(b) How can you help Khairul in his test? Explain why.

Reflect on the properties of
an alkali:

Tastes bitter and feels
slippery

Corrosive
 Has pH value more than 7
 Changes moist red
litmus paper to blue

Ti spLiteracy

Figure 6.8

142

Interaction between MatterTHEME 3
pH Value6.2

Based on the pH value mentioned by Zahir, do clownfish require acidic or alkaline water?
Why do you say so?

The pH scale which ranges from 0 to 14 is used to show the acidity and alkalinity of an
aqueous solution. Solutions with pH value less than 7 is acidic while solutions with pH value
more than 7 is alkaline. Universal indicator, pH meter or pH paper is commonly used to
determine the pH value. Referring to Figure 6.10, what is the relationship between pH value and
degree of acidity or alkalinity?

More acidic More alkaline
Neutral

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Figure 6.10 The pH scale

What is actually ̒pH̕? In chemistry, pH is a logarithmic measure of the concentration of
hydrogen ions in an aqueous solution.

pH = –log [H+]

where log is logarithm of base 10 and [H+] is the concentration of hydrogen ions in mol dm–3 of
the solution. Using that formula, we can determine the pH value of an acid by calculation.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.2.1 State the meaning of pH

and its uses
6.2.2	 Calculate	pH	values	of

acids	and	alkalis
6.2.3 Investigate the

relationship between
pH value and the
concentration	of	hydrogen
ions	and	hydroxide	ions
through experiment

The pH Values of Acids and Alkalis

The clownfish that
I am rearing need
water with pH
values between
8.0 to 8.3 in
order for them
to be healthy.

I am taking a sample of
water to test the pH value
of water in this aquarium.

Zahir, what are you doing?

Figure 6.9 Clownfish need water with specific pH values

137

Acid, Base and Salt CHAPTER 6
The concentration of hydroxide ion, OH– is used to calculate the value of pOH of an alkali
based on the following formula, where [OH–] represents the concentration of hydroxide ions in
mol dm–3 of the alkali solution.

pOH = –log [OH–]

Given that the sum of pH value and pOH value is 14, the pH value of an alkali can be
calculated by using the following relationship:

pH + pOH = 14
 pH = 14 – pOH

Calculate the pH value of nitric acid, HNO3 with 0.5 mol dm–3 of hydrogen ion, H+.
Solution

Given the concentration of H+ = 0.5 mol dm–3

pH = –log [0.5] Use the formula pH = –log [H+]
 = –(– 0.301)
 = 0.301
pH value of nitric acid, HNO3 = 0.3

Example 1

Calculate the pOH value for sodium hydroxide solution, NaOH with 0.1 mol dm–3 hydroxide
ions, OH–.

Solution

Given that the concentration of hydroxide ion, OH– = 0.1 mol dm–3

pOH = –log [0.1] Use the formula pOH = –log [OH–]
 = –(–1)
 = 1
pOH value of sodium hydroxide solution, NaOH = 1.0

Example 3

Determine the molarity of hydrochloric acid, HCl with pH value of 2.0.
Solution

pH = –log [H+]
 2.0 = –log [H+]
 log [H+] = –2.0
 [H+] = 10–2

= 0.01 mol dm–3

Molarity of hydrochloric acid, HCl = 0.01 mol dm–3

Example 2

144

Interaction between MatterTHEME 3
The pH value can be calculated based on the concentration of hydrogen ions, H+ in an acid,
or the concentration of hydroxide ions, OH– in an alkali. So, the pH scale allows us to compare
the concentration of hydrogen ions, H+ or the hydroxide ions, OH– in an aqueous solution. The
relationship between hydrogen ions, H+ or hydroxide ions, OH– with the pH value can be studied
in Experiment 6.3.

Calculate the pH value for potassium hydroxide, KOH that has 0.01 mol dm–3 hydroxide
ions, OH–.

Solution

Given concentration of hydroxide ion, OH– = 0.01 mol dm–3

pOH = –log [0.01] Use the formula pOH = –log [OH–]
 = –(–2)
 = 2
pOH value of potassium hydroxide solution, KOH = 2.0
pH value of potassium hydroxide solution, KOH = 14.0 – pOH Consider the relationship:

pH + pOH = 14
  = 14.0 – 2.0
  = 12.0

Example 4

Determine the molarity of lithium hydroxide solution, LiOH with pH value 12.0.

Solution

pH + pOH = 14.0
 12.0 + pOH = 14.0
 pOH = 14.0 – 12.0
  = 2.0
 pOH = –log [OH–]
 2.0 = –log [OH–]
 log [OH–] = –2.0
 [OH–] = 10–2

= 0.01 mol dm–3

Molarity of lithium hydroxide solution, LiOH = 0.01 mol dm–3

Example 5

Did you know that the decimal place of pH
is related to the significant numbers in the
concentration of hydrogen ions given?

If the value of given concentration has
two significant numbers, the pH value
should be rounded to two decimal places.

137

Acid, Base and Salt CHAPTER 6
Experiment 6.3

Aim: To study the relationship between the concentration of hydrogen ions, H+ and pH value
of acid.

Problem statement: Does the concentration of hydrogen ions, H+ of an acid affect its pH value?
Hypothesis: The higher the concentration of hydrogen ion, H+, the lower the pH value of the acid.
Variables:

(a) Manipulated : Concentration of hydrogen ions, H+

(b) Responding : pH value
(c) Fixed : Type of acid
Materials: 0.1 mol dm–3, 0.01 mol dm–3 and 0.001 mol dm–3 hydrochloric acid, HCl
Apparatus: 100 cm3 beaker and pH meter
Procedure:

1. Pour 20 cm3 of hydrochloric acid, HCl of different concentrations into three beakers.
 2. Measure the pH value of each hydrochloric acid, HCl with the pH meter.
 3. Record the pH values in Table 6.2.
Results:

Table 6.2

Concentration of hydrochloric acid, HCl (mol dm–3) 0.1 0.01 0.001

Concentration of hydrogen ions, H+ (mol dm–3)

pH value

Interpreting data:

1. Based on the results obtained, how does the pH value change when the concentration of
hydrochloric acid, HCl decreases?

2. State the changes in the concentration of hydrogen ions, H+ when the concentration of
hydrochloric acid, HCl decreases.

3. What is the relationship between the concentration of hydrogen ions, H+ and pH value?
Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?
Discussion:

1. When an acidic solution is diluted, what are the changes in the:
(a) Concentration of hydrogen ions, H+?
(b) pH value?
(c) Degree of acidity of the aqueous solution?

2.  State the relationship between the concentration of hydrogen ions, H+, pH values and degree
of acidity of an acidic aqueous solution.

Prepare a complete report after carrying out this experiment.

146

Interaction between MatterTHEME 3
When the concentration of acid increases, more acid molecules ionise to produce hydrogen
ions, H+. The higher the concentration of hydrogen ions, H+, the lower the pH value. Acidity
increases when the pH value of the acid solution decreases.

Concentration of hydrogen ions, H+ , pH value

On the other hand, the higher the concentration of hydroxide ions, OH–, the higher the pH
value. Alkalinity increases when the pH value of the alkaline solution increases.

Concentration of hydroxide ions, OH– , pH value

Experiment 6.4

Aim: To study the relationship between the concentration of hydroxide ions, OH– and pH value of
an alkali.

Problem statement: Does the concentration of hydroxide ions, OH– of an alkali affect its
pH value?

Hypothesis: Make a suitable hypothesis for this experiment.
Variables: State all variables involved in this experiment.
Materials: 0.1 mol dm–3, 0.01 mol dm–3 and 0.001 mol dm–3 sodium hydroxide solution, NaOH
Apparatus: 100 cm3 beaker and pH meter
Procedure:

1. Plan the procedure to measure the pH value of sodium hydroxide solution, NaOH.
 2. Your plan should include the pH meter.
 3. Carry out the experiment with your teacher̕s permission.
 4. Record the pH values obtained in your report book.
Results:

Record the pH values in a table.
Interpreting data:

1. Based on the data obtained, how does the pH value change when the concentration of sodium
hydroxide solution, NaOH decreases?

2. When the concentration of sodium hydroxide solution, NaOH decreases, what are the changes
that occur to the:
(a) Concentration of hydroxide ions, OH–?
(b) pH value?
(c) Degree of alkalinity of sodium hydroxide solution, NaOH?

3. State the relationship between the concentration of hydroxide ions, OH–, pH value and degree
of alkalinity of sodium hydroxide, solution NaOH.

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Prepare a complete report after carrying out this experiment.

137

Acid, Base and Salt CHAPTER 6
Most substances found in our daily lives contain acids or
alkalis. The determination of pH values for these substances can
be done in Activity 6.2.

Figure 6.11 The pH value of few items in daily life tested with the universal indicator

Activity 6.2
Determining the pH values of various items in daily life

1. You are supplied with the following items:

• Soap water • Milk tea • Carbonated drink
• Lime juice • Coffee • Tap water

2. In pairs, measure the pH value of each item using the universal indicator.
 3. Record the items with similar pH values.
 4. Prepare a pH indicator using a purple cabbage. Visit websites to know how to prepare this pH

indicator. Use the pH indicator that you have prepared to measure the pH value of each of the
above items.

5. Using a suitable graphic management tools, present your findings.
 6. Pin up your work in class to share with others.

Yourself
TestTest

6.2

1. Write the formula to calculate the pH value of acid.
 2. Calculate the pH value for hydrochloric acid, HCl that contains 0.001 mol dm–3 hydrogen

ions, H+.
 3. Determine the pH value for calcium hydroxide, Ca(OH)2 with concentration of
  0.05 mol dm–3. [pH + pOH = 14].

Sewage pipe
 Battery Lemon Tomato Milk Blood Antacid Soap cleaner

Gastric juice Vinegar Coffee Water Baking soda Ammonia Bleach
      solution

Bleach
AmmoniaBaking soda

Milk

148

Interaction between MatterTHEME 3

Purple cabbages change
colour at
different
pH values.

Chemistry& Us
Can you tell the similarities
or the differences between
these two acids? Teacher, both acids

are monoprotic.

Hydrogen ions, H+ are
produced when acid is
dissolved in water.

HCl is a strong
acid, CH3COOH is
a weak acid.

Strength of Acids and Alkalis6.3

Figure 6.12 Similarities and differences between two acids

Strong Acids and Weak Acids

The strength of an acid depends on the degree of dissociation or
ionisation of the acid in water.

Strong Acids

A strong acid is an acid that ionises completely in water to
produce a high concentration of hydrogen ions, H+. Hydrochloric
acid, HCl is a strong acid because all molecules of hydrogen
chloride, HCl that dissolve in water are ionised completely
to hydrogen ions, H+ and chloride ions, Cl–. No molecule of
hydrogen chloride, HCl exists in this solution.

HCl(aq) → H+(aq) + Cl–(aq)

Water

Hydrogen
chloride gas, HCl

Hydrogen chloride
molecule, HCl

Hydrogen ion, H+

Chloride ion, Cl–

Figure 6.13 Complete ionisation of hydrogen chloride, HCl

Observe Figure 6.12. What is meant by a strong acid and a weak acid?

ChemistryChemistry

Hydrogen ions, H+ produced
from acid molecules
will combine with water
molecules to form
hydroxonium ions, H3O

+.
The hydroxonium ions, H3O

+

is the product of a dative
bond formed between
hydrogen ion, H+ with
water molecule.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.3.1	 Define	strong	acid,

weak	acid,	strong	alkali
and	weak	alkali

6.3.2 Explain the strength
of	acid	and	alkali
based on its degree of
dissociation	in	water

137

Acid, Base and Salt CHAPTER 6
Strong Alkalis and Weak Alkalis

Alkalis also consist of strong alkalis and weak alkalis depending on their degree of ionisation
in water.

Strong Alkalis

A strong alkali is an alkali that ionises completely in water to produce a high concentration
of hydroxide ions, OH–. Sodium hydroxide, NaOH is a strong alkali that undergoes complete
dissociation when dissolved in water. Only sodium ions, Na+ and hydroxide ions, OH– are present
in the solution.

NaOH(aq) → Na+(aq) + OH–(aq)

Sodium ion, Na+

Hydroxide ion, OH–Sodium hydroxide
solution, NaOH

Figure 6.15 Complete ionisation of sodium hydroxide solution, NaOH

Dissociation is also known
as ionisation.

Ti spLiteracy

Weak Acids

A weak acid is an acid that ionises partially in water to produce low concentration of hydrogen
ions, H+. Ethanoic acid, CH3COOH is a weak acid because the molecules of ethanoic acid,
CH3COOH ionise partially in water. The degree of dissociation of ethanoic acid molecules is 1.54%.
In other words, from 100 molecules of ethanoic acid, CH3COOH, only one molecule of ethanoic
acid, CH3COOH ionises to hydrogen ions, H+ and ethanoate ions, CH3COO–. The rest still exist as
molecules of ethanoic acid, CH3COOH.

CH3COOH(aq)   H+(aq) + CH3COO–(aq)

Ethanoic acid,
CH3COOH molecule

Ethanoic acid,
CH3COOH molecule

Ethanoate ion,
CH3COO–

Hydrogen ion, H+

Water

Glacial ethanoic acid,
CH3COOH

Ethanoic acid,
CH3COOH

Figure 6.14 Partial ionisation of ethanoic acid, CH3COOH

The reversible arrow shows that
ethanoic acid, CH3COOH molecule
can form hydrogen ions, H+ and
ethanoate ions, CH3COO–. These
ions can also combine again to
form the acid molecules.

150

Interaction between MatterTHEME 3
Weak Alkalis

A weak alkali is an alkali that ionises partially in water to produce a low concentration of
hydroxide ions, OH–. Ammonia solution, NH3 is a weak alkali because ammonia molecules, NH3
ionise partially in water. The degree of dissociation of ammonia, NH3  is 1.3%. In other words,
from 100 molecules of ammonia, NH3 only one molecule of ammonia, NH3  will receive hydrogen
ion, H+ from water molecule. So, only a small number of hydroxide ions, OH– is present in
the solution.

NH3(aq) + H2O(l)   NH4
+(aq) + OH–(aq)

Ammonia gas, NH3

Ammonia molecule, NH3

Hydroxide ion, OH–

Ammonium ion, NH4
+

Ammonia molecule, NH3

Water

Figure 6.16 Partial ionisation of ammonia solution, NH3

Activity 6.3
Carry out a simulation to explain the strength of acids and alkalis

1. Visit the website given.
 2. Vary the regulator for acid strength and observe the degree

of dissociation and number of hydrogen ions, H+ present.
 3. Repeat step 2 for alkali and observe the degree of

dissociation and number of hydroxide ions, OH–  present.
 4. Interpret the information on strength of acids and alkalis based on the degree of dissociation.
 5. Relate the concentration of hydrogen ions, H+ and hydroxide ions, OH– with the degree of

dissociation of the acid and alkali.
 6. Display your findings in an interesting presentation.

Yourself
TestTest

6.3

1. Give the meaning of the following terms:
(a) Strong acid (c) Strong alkali
(b) Weak acid (d) Weak alkali

2. Why does ammonia solution, NH3 that has the same concentration as potassium
hydroxide, KOH have a lower pH value?

3. The pH value 0.1 mol dm-3 nitric acid, HNO3 is different from the pH value 0.1 mol dm–3
oxalic acid, H2C2O4? Explain.

CTCentury
Skills21st

Simulation on acid
and alkali

http://bit.ly/31cGoMQ

137

Acid, Base and Salt CHAPTER 6
Figure 6.17 To inflate the balloon using vinegar and baking soda

Have you ever inflated a balloon using vinegar and baking soda?
Is this process related to the chemical properties of acid?

Chemical Properties of Acid

The properties of acid is divided into physical and chemical
properties. The properties of acid such as having a sour taste,
changing moist blue litmus paper to red and having pH values less
than 7 are the physical properties of acid. The chemical properties
of acid on the other hand refer to the reactions between acid and
other substances. Carry out activity 6.4 to study the chemical
properties of acid.

Aim: To study the chemical properties of acids.
Materials: Copper(II) oxide powder, CuO, zinc powder, Zn, marble chips, CaCO3, 1.0 mol dm–3

sulphuric acid, H2SO4, 2.0 mol dm–3 nitric acid, HNO3, 2.0 mol dm–3 hydrochloric
acid, HCl, limewater, wooden splinter and filter papers

Apparatus: 100 cm3 beaker, glass rod, filter funnel, retort stand with clamp, evaporating dish,
Bunsen burner, pipeclay triangle, delivery tube and rubber stopper, tripod stand,
spatula, test tubes and test tube holder

Reaction between acid and base

Procedure:

1. Pour 20 cm3 of 1.0 mol dm–3 sulphuric acid, H2SO4 into a beaker. Heat the acid by using a small flame.
 2. Add copper(II) oxide powder, CuO gradually into the acid by using a spatula. Stir the mixture

with a glass rod.
 3. Observe the change that takes place on copper(II) oxide, CuO that reacts with acid. Record

your observation on the solution produced.

Activity 6.4

Chemical Properties of Acids and Alkalis6.4

Balloon filled with
baking soda

Vinegar

After 30
seconds

Carbon
dioxide gas

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.4.1	 Summarise	the	chemical

properties	of	acids
by	carrying	out	the
reactions	between:

•	 Acid	and	base
	 •	 Acid	and	reactive

metal
	 •	 Acid	and	metal

carbonate
6.4.2	 Summarise	the	chemical

properties	of	alkalis
by	carrying	out	the
reactions	between:

•	 Alkali	and	acid
	 •	 Alkali	and	metal	ion
	 •	 Alkali	and

ammonium salt

Balloon inflation

http://bit.ly/2Mh3M7y

152

Interaction between MatterTHEME 3
4. Continue adding copper(II) oxide powder, CuO until it can no longer dissolve.
 5. Filter out the excess copper(II) oxide, CuO from the mixture.
 6. Pour the filtrate into an evaporating dish and heat the filtrate until one third of its initial

volume remains.
 7. Allow the saturated solution produced to cool until salt crystals are formed.
 8. Filter the contents of the evaporating dish to obtain the salt crystals. Rinse the crystals with

distilled water.
 9. Dry the salt crystals between two pieces of filter papers.
10. Observe the physical properties of the salt crystals and record your findings.

Heat

Pipeclay
triangle

Evaporating dish

Salt crystals

Filtrate

Glass rod

Hot 20 cm3 of 1.0 mol dm–3

sulphuric acid, H2SO4

Spatula
Excess of
copper(II) oxide
powder, CuO

Filter funnel

Filter paper

Residue
(excess of copper(II)
oxide powder, CuO)

Filtrate (copper(II) sulphate
solution, CuSO4)

Figure 6.18 Preparation of salt crystals from the reaction between acid and base

Discussion:

1. What happens to the copper(II) oxide powder, CuO when added to sulphuric acid, H2SO4?
 2. What is the colour of the solution produced from the reaction between sulphuric acid, H2SO4

and copper(II) oxide, CuO?
 3. Write a chemical equation for the reaction between sulphuric acid, H2SO4 and copper(II)

oxide, CuO.
 4. From the chemical equation written above, complete the following equation in words:

Acid + Base →  +

137

Acid, Base and Salt CHAPTER 6
Reaction between acid and reactive metal

Procedure:

1. Plan a procedure to study the reaction between hydrochloric acid, HCl and zinc powder, Zn as
shown in Figure 6.19.

Heat

Pipeclay triangle

Evaporating dish

Salt crystals

Filtrate

Glass rod

20 cm3 of  2.0 mol dm–3

hydrochloric acid , HCl

Spatula
Excess of zinc
powder, Zn

Filter funnel

Filter paper

Residue (excess of zinc
powder, Zn)

Filtrate (zinc chloride
solution, ZnCl2)

Figure 6.19 Preparation of salt crystals from the reaction between acid and reactive metal

2. Discuss with your teacher if you have
encountered any problems when
planning the procedure.

3. Make sure that you carry out the
chemical test on the gas released as
shown in Figure 6.20.

4. Carry out this test with your
teacher̕s permission.

5. Record your observations.
Discussion:

1. What is the observation that indicates acid has reacted with metal when zinc powder, Zn is
added to hydrochloric acid, HCl?

2. Name the gas released in this activity.
 3. Write a chemical equation for the reaction between hydrochloric acid, HCl and zinc, Zn.
 4. From the chemical equation written above, complete the following equation in words:

Acid + Reactive metal →  +

Figure 6.20

Burning
wooden
splinter

5 cm3 of
2.0 mol dm–3

hydrochloric
acid, HCl

Zinc powder, Zn

154

Interaction between MatterTHEME 3
Reaction between acid and metal carbonate

Procedure:

1. Plan a procedure to carry out this activity to study the reaction between nitric acid, HNO3
and marble chips, CaCO3.

2. Include safety measures taken in your procedure.
 3. Discuss with your teacher if you have encountered any problems when planning
  the procedure.
 4. Make sure that you carry out the chemical test on the gas released as shown in Figure 6.21.

Marble chips, CaCO3

5 cm3 of 2.0 mol dm–3

nitric acid, HNO3

Limewater

Figure 6.21

5. Carry out this test with your teacher̕s permission.
 6. Record your observations.
Discussion:

1. What is the reason for using excess marble chips, CaCO3 to react with nitric acid, HNO3?
 2. How do you remove the excess marble chips, CaCO3 from the salt solution produced?
 3. For the reaction in this activity:

(a) Name the salt produced
(b) Name the gas released

4. Write a chemical equation for the reaction between nitric acid, HNO3 and marble chips, CaCO3.
 5.  From the chemical equation written above, complete the following equation in words:

Acid + Metal carbonate →  +  +

From Activity 6.4 that was carried out, it can be summarised that acids have the following
chemical properties:

Acids react with bases to produce salt and water
 Acids react with reactive metals to produce salt and hydrogen gas, H2
 Acids react with metal carbonates to produce salt, water and carbon dioxide
gas, CO2

Prepare a complete report after carrying out this activity.

137

Acid, Base and Salt CHAPTER 6
Chemical Properties of Alkalis

Chemical properties of alkalis can be determined through Activity 6.5.

Aim: To study the chemical properties of alkali.
Materials: Benzoic acid powder, C6H5COOH, 1.0 mol dm–3 sodium hydroxide solution, NaOH,

ammonium chloride powder, NH4Cl, copper(II) sulphate solution, CuSO4, distilled
water, filter paper and red litmus paper

Apparatus: 100 cm3 beaker, glass rod, filter funnel, retort stand with clamp, evaporating dish,
Bunsen burner, pipeclay triangle, tripod stand, dropper, spatula, test tube, boiling
tube and test tube holder

Figure 6.22, Figure 6.23 and Figure 6.24 show three reactions involving alkalis.

Heat

Pipeclay triangle

Evaporating dish

Salt crystals Filtrate

Glass rod

20 cm3 of 1.0 mol dm–3 sodium
hydroxide solution, NaOH

Spatula
Benzoic acid powder,
C6H5COOH

Filter funnel

Filter paper

Residue (excess acid powder)

Filtrate

Figure 6.22 Preparation of salt crystals from the reaction between alkali and acid

Activity 6.5

Figure 6.24  Addition of alkali to metal
ions to produce insoluble metal
hydroxide precipitate

Figure 6.23  Heating the mixture of alkali
and ammonium salt to produce
ammonia gas

Heat

Moist red
litmus paperAmmonium chloride

powder, NH4Cl

1.0 mol dm–3

sodium hydroxide
solution, NaOH

1.0 mol dm–3

sodium hydroxide
solution, NaOH

Copper(II) sulphate
solution, CuSO4

Blue
precipitate

156

Interaction between MatterTHEME 3

156
Procedure:

1. Based on Figure 6.22 to Figure 6.24, plan a laboratory activity to study the chemical properties
of alkalis.

2. Plan and write out the procedure for the laboratory activity to be discussed with your teacher.
 3. Record your observations in a report book.
 4. Write an equation in words to summarise the chemical properties of alkalis.

Chemical
properties

of acids

Acid + Base → Salt + Water

Example: 2HNO3(aq)        +        CuO(s)        →        Cu(NO3)2(aq)        +        H2O(l)
 Nitric acid Copper(II) oxide Copper(II) nitrate Water

Acid + Reactive metal → Salt + Hydrogen gas

Example: H2SO4(aq)        +        Zn(s)        →        ZnSO4(aq)        +        H2(g)
 Sulphuric acid  Zinc Zinc sulphate  Hydrogen gas

Acid + Metal carbonate → Salt + Water + Carbon dioxide gas

Example: 2HCl(aq)     +     CaCO3(s)     →     CaCl2(aq)     +     H2O(l)     +     CO2(g)
         Hydrochloric acid Calcium carbonate   Calcium chloride Water Carbon dioxide gas

Chemical
properties
of alkalis

Alkali + Acid → Salt + Water

Example: 2KOH(aq)      +      H2SO4(aq)      →      K2SO4(aq)      +      2H2O(l)
 Potassium hydroxide Sulphuric acid  Potassium sulphate Water

Alkali + Ammonium salt → Salt + Water  + Ammonia gas

Example: KOH(aq)      +       NH4Cl(aq)       →      KCl(aq)      +     H2O(l)     +     NH3(g)
 Potassium hydroxide Ammonium chloride Potassium chloride Water Ammonia gas

Alkali + Metal ion → Insoluble metal hydroxide + Cation from alkali

Example: 2NaOH(aq)      +      Mg2+(aq)      →      Mg(OH)2(s)      +      2Na+(aq)
 Sodium hydroxide Magnesium ion  Magnesium hydroxide Sodium ion

Prepare a complete report after carrying out this activity.

From Activity 6.5 that was carried out, we can summarise that alkalis have the following
chemical properties:

Alkalis react with acids to produce salt and water
 When a mixture of alkali and ammonium salt is heated, ammonia gas, NH3 is released
 Addition of an alkali to most metal ions, will produce an insoluble metal hydroxide precipitate

Table 6.3 summarises the chemical properties of acids and alkalis

Table 6.3 Chemical properties of acids and alkalis

137

Acid, Base and Salt CHAPTER 6
Figure 6.25 Concentration of tea affects its colour

Concentration of a solution is a measurement that shows the quantity of solute dissolved in a
unit volume of solution, normally in 1 dm3 solution. The higher the quantity of solute, the higher
the concentration of the solution. The quantity of solute dissolved can be measured in gram or
mole, hence the concentration of a solution can be measured in unit g dm–3 or mol dm–3.

Yourself
TestTest

6.4

1. Write a chemical equation for the reaction between hydrochloric acid, HCl and:
(a) Barium hydroxide, Ba(OH)2

(b) Magnesium, Mg
(c) Zinc carbonate, ZnCO3

2. Write an equation in words to summarise the reaction of an alkali solution and the
following substances:
(a) Dilute acids
(b) Ammonium salts
(c) Metal ions

Concentration of Aqueous Solution6.5

Dad, why is the colour
of my tea is different
from the one that you
are drinking?

LearningLearning
StandardStandard

At the end of the lesson, pupils
are able to:
6.5.1 State the meaning

of concentration of
aqueous solution

6.5.2 Solve numerical problems
involving concentration
of solution

Because the concentration of
tea in our glasses are different.

Concentration in unit g dm–3, is the mass of solute found in 1 dm3 solution.

Concentration (g dm–3) =  Mass of solute (g)
Volume of solution (dm3)

Concentration in unit mol dm–3, is the number of moles of solute found in 1 dm3 solution.
This concentration is called molarity.

Molarity (mol dm–3) = Number of moles of solute (mole)
Volume of solution (dm3)

158

Interaction between MatterTHEME 3
Figure 6.26 Relationship between concentration and molarity

Calculate the concentration in g dm–3, for each solution produced.
(a) 40 g of solid copper(II) sulphate, CuSO4 is dissolved in water to produce 20 dm3 solution.
(b) 18 g of sodium hydroxide pellets, NaOH is dissolved in water to produce 750 cm3 solution.

Solution

(a)  Concentration of copper(II) sulphate, CuSO4 = Mass of solute (g)
Volume of solution (dm3)

= 40 g
20 dm3

= 2.0 g dm–3

(b) Concentration of sodium hydroxide, NaOH

= Mass of solute (g)
Volume of solution(dm3)

= 18 g
0.75 dm3

= 24.0 g dm–3

Example 6

Concentration
(g dm–3)

Molarity
(mol dm–3)

÷ molar mass

× molar mass

Calculate the molarity of each solution prepared.
(a) 10 mol of solid zinc chloride, ZnCl2 dissolved in water to produce 5 dm3 of solution.
(b) 0.1 mol of solid calcium chloride, CaCl2 is dissolved in 500 cm3 of distilled water.

Solution

(a) Molarity of zinc chloride solution, ZnCl2 = Number of moles of solute (mol)
Volume of solution (dm3)

= 10 mol
5 dm3

= 2.0 mol dm–3

(b) Molarity of calcium chloride solution, CaCl2

= Number of moles of solute (mol)
Volume of solution (dm3)

= 0.1 mol
0.5 dm3

= 0.2 mol dm–3

Example 7

750 cm3 is converted
to dm3 by dividing the
volume with 1000.

750
1000  dm3

= 0.75 dm3

The unit for molarity is mol dm–3 or
molar (M). You have to remember
that mole is not the same as molar.
Mole is the unit for measuring matter
while molar is the number of moles of
solute in a given volume of solution.

Ti spLiteracy

500 cm3 is converted
to dm3 by dividing the
volume with 1000.

500
1000  dm3

= 0.5 dm3

159

Acid, Base and Salt CHAPTER 6
We can calculate number of moles of solute dissolved in the solution if its molarity and the
volume of the solution are known.

Molarity = Number of moles of solute (mol)
Volume of solution (dm3)

M = n
V

Therefore, n = MV
Volume of solution
is in dm3.

If the volume of the solution is in
cm3, thus, unit of volume needs to be
converted to dm3.
 n = M( V

1000 )
Therefore, n = MV

1000  Volume of
solution is
in cm3.

Calculate the number of moles of potassium hydroxide, KOH found in 2 dm3 of
0.5 mol dm–3 potassium hydroxide solution, KOH.

Solution

Number of moles, n = MV
  = 0.5 mol dm–3 × 2 dm3

= 1 mol KOH

Example 10

This formula is applied because
the volume of solution is in dm3.

What is the concentration of nitric acid, HNO3 with a molarity of 0.5 mol dm–3 in unit g dm–3?
[Relative atomic mass: H = 1, N = 14, O = 16]

Solution

Concentration = Molarity × Molar mass HNO3

RAM H RAM N RAM O

= 0.5 mol dm–3 × [1 + 14 + 3(16)] g mol–1

= 0.5 mol dm–3 × 63 g mol–1

= 31.5 g dm–3

Example 8

Convert the concentration of 3.6 g dm–3 lithium hydroxide solution, LiOH to molarity, mol dm–3.
[Relative atomic mass: H = 1, Li = 7, O = 16]

Solution

Molarity = Concentration
Molar mass LiOH

=  3.6 g dm–3

(7 + 16 + 1) g mol–1

RAM Li RAM O RAM H
 = 0.15 mol dm–3

Example 9

160

Interaction between MatterTHEME 3
Activity 6.6
Solving numerical problems related to concentration of solutions

1. 6 g of solid magnesium sulphate, MgSO4 is added into a beaker containing 200 cm3 of water.
Calculate the concentration in g dm–3, for the solution produced.

2. 0.4 mol of zinc chloride, ZnCl2 is dissolved in water to produce 2 dm3 of solution. Calculate the
molarity of the solution prepared.

3. What is the concentration of 0.5 mol dm–3 sulphuric acid, H2SO4 in g dm–3?
  [Relative atomic mass: H = 1, O = 16, S = 32]

4. The concentration of sodium chloride solution, NaCl is 1.989 g dm–3. Calculate the molarity of
the solution in mol dm–3.

[Relative atomic mass: Na = 23, Cl = 35.5]

5. Calculate the number of moles of sodium hydroxide, NaOH in 2.5 dm3 of 0.2 mol dm–3 sodium
hydroxide solution, NaOH.

6. Given the molarity of 250 cm3 of barium hydroxide solution, Ba(OH)2 is 0.1 mol dm–3.
  How many moles of hydroxide ion, OH– is in the solution?

Yourself
TestTest

6.5

1. What is meant by concentration in unit g mol–1?
 2. State two units to measure concentration.
 3. 0.03 mol of potassium nitrate, KNO3 is dissolved in 1.2 dm3 of distilled water. What is the

molarity of the potassium nitrate solution, KNO3 produced?
 4. Calculate the concentration of sulphuric acid, H2SO4 that has the molarity of 2.0 mol dm–3 in

unit g dm–3.
  [Relative atomic mass: H = 1, O = 16, S = 32]
 5. 1.9 g MgY2 is dissolved in 100 cm3 of water to produce a solution with the molarity of

0.2 mol dm–3. What is the relative atomic mass of Y?
  [Relative atomic mass: Mg = 24]

A beaker contains 200 cm3 of 0.2 mol dm–3 lead(II) nitrate solution, Pb(NO3)2. How many moles
of lead(II) nitrate, Pb(NO3)2 is in the beaker?

Solution

Number of moles, n = MV
1000  This formula is applied because

the volume of solution is in cm3.

= 0.2 mol dm–3 × 200 cm3

1000
 = 0.04 mol Pb(NO3)2

Example 11

CT

161

Acid, Base and Salt CHAPTER 6
Activity

Standard Solution6.6
Have you seen the syrup dispenser as
shown in Photograph 6.2? Did you know
that the dispenser is filled with a standard
solution of sugar so that the machine can
dispense sugar at an amount requested
by customers? What do you know about
standard solution?

Syrup dispenser

http://bit.ly/35Ajhiv

Meaning of Standard Solution

Most chemical reactions involve reactants in aqueous solution.
In that case, the preparation of aqueous solution with specific
concentrations is very important. Standard solution is a solution
with known concentration. In the preparation of standard
solutions, mass of solute and volume of distilled water are two
parameters that have to be measured accurately.

Preparation of a Standard Solution from a Solid

6.7

Photograph 6.2
Syrup dispenser

Aim: To prepare 250 cm3 of standard solution of 1.0 mol dm–3 sodium carbonate, Na2CO3.
Materials: Distilled water and solid sodium carbonate, Na2CO3

Apparatus: Electronic balance, filter funnel, 250 cm3 volumetric flask, dropper, wash bottle,
250 cm3 beaker and glass rod

Procedure:

1. Determine the mass of sodium carbonate, Na2CO3 needed using the formula n = MV

1000 .
 2. Weigh the mass calculated using the electronic balance.
 3. Add 100 cm3 of distilled water to the solid sodium carbonate, Na2CO3 in a beaker.
 4. Stir the mixture with a glass rod until all the solid sodium carbonate, Na2CO3 is completely

dissolved in the distilled water.

5. Transfer the sodium carbonate solution, Na2CO3 into a 250 cm3 volumetric flask via a
  filter funnel.
 6. Rinse the beaker with distilled water. Make sure all the remaining solution is transferred into

the volumetric flask.
 7. Then, rinse the filter funnel with a little distilled water. All the remaining solution is

transferred into the volumetric flask.
 8. Remove the filter funnel. Add distilled water until it approaches the calibration mark on the

volumetric flask.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.6.1 State the meaning of

standard solution
6.6.2 Describe the preparation

of a standard solution
through activity:

•	 From	a	solid
substance

•	 Through	dilution	of
an aqueous solution

6.6.3 Solve numerical
problems involving
preparation of standard
solution and dilution

162

Interaction between MatterTHEME 3
Sodium hydroxide, NaOH is not suitable to be used for the preparation of a standard solution
because sodium hydroxide, NaOH is hygroscopic (absorbs water or moisture in the air). Sodium
hydroxide, NaOH also absorbs carbon dioxide gas, CO2 in the air to form sodium carbonate, Na2CO3.

2NaOH(s) + CO2(g) → Na2CO3(s) + H2O(l)

This causes difficulty to determine the exact mass of sodium hydroxide, NaOH. Therefore, the
preparation of a standard solution of sodium hydroxide, NaOH with a known concentration could
not be made.

9. Using a dropper, add distilled water slowly until the meniscus level is aligned exactly on the
calibration mark of the volumetric flask.

10. Close the volumetric flask with a stopper. Shake well by inverting the volumetric flask several
times until the solution is homogenous.

Note: Keep the standard solution of sodium carbonate, Na2CO3 that you have prepared for Activity 6.8.

(a) Add distilled water (b) Dissolve the solid (c) Transfer the solution into a
 volumetric flask

(f) Close the volumetric flask with
     a stopper before shaking

(e) Add distilled water until
     calibration mark

(d) Rinse the filter funnel with
     distilled water

Distilled
water

Solid sodium
carbonate, Na2CO3 Glass rod

Filter funnel

Calibration
markVolumetric

flask

Stir

Distilled water

Meniscus
level of
solution

Calibration
mark

Meniscus
level of
solution

Dropper

Calibration
mark

Stopper

Figure 6.27 Preparation of 1.0 mol dm–3 sodium carbonate solution, Na2CO3 from a solid
Discussion:

1. Why must the beaker and filter funnel be rinsed with distilled water?
 2. Why must all the remaining solution be transferred into the volumetric flask?
 3. How can you ensure that the meniscus level aligns with the calibration mark of the

volumetric flask?
 4. Why does the volumetric flask need to be closed after the standard solution is prepared?

Prepare a complete report after carrying out this activity.

163

Acid, Base and Salt CHAPTER 6
Preparation of a Standard Solution by Diluting Aqueous Solution

Another method of preparing solutions of known concentration is by dilution method. This
method involves adding water to a concentrated standard solution, or known as stock solution, to
produce a more diluted solution.

During dilution, water that is added to the aqueous solution will alter the concentration of
the solution but it would not alter the number of moles of solute contained in the solution.

(a) Concentrated solution (b) Dilute solution

Solute
Solute

Add distilled water

Figure 6.28 Quantity of solute remains the same in both solutions of different concentrations
Hence,
Number of moles of solute before dilution = Number of moles of solute after dilution
 n1 = n2

M1V1

1000  =
M2V2

1000

M1V1 = M2V2

where M1 is the molarity of aqueous solution (stock solution) before dilution.
 V1 is the volume of aqueous solution (stock solution) before dilution.
 M2 is the molarity of aqueous solution (prepared solution) after dilution.
 V2 is the volume of aqueous solution (prepared solution) after dilution.

As an example, you wish to prepare 500 cm3 of 0.1 mol dm–3 copper(II) sulphate solution, CuSO4
from the stock solution of 2.0 mol dm–3 copper(II) sulphate, CuSO4. Use the following formula:

M1V1 = M2V2
 (2.0)(V1) = (0.1)(500)

V1 = (0.1)(500)
2.0

= 25 cm3

Hence, 25 cm3 of stock solution of copper(II) sulphate, CuSO4 needs to be diluted using distilled
water until 500 cm3 solution of copper(II) sulphate, CuSO4 is obtained.

ChemistryChemistry

Sodium carbonate, Na2CO3 that is used to prepare standard solutions is alkaline. When sodium
carbonate, Na2CO3 is dissolved in distilled water, carbonate ions, CO3

2– react with water molecules
to produce bicarbonate ions, HCO3

– and hydroxide ions, OH–. The presence of hydroxide ions, OH–
gives the alkaline properties to the solution.

CO3
2–(aq) + H2O(l) → HCO3

–(aq) + OH–(aq)

Solid oxalic acid H2C2O4.2H2O can be used to prepare a standard solution in the laboratory.

164

Interaction between MatterTHEME 3
The preparation of a standard solution by dilution method can be carried out through
Activity 6.8 using sodium carbonate solution, Na2CO3

prepared in Activity 6.7.

Activity 6.8
Aim: To prepare 100 cm3 of standard solution of 0.2 mol dm–3 sodium carbonate, Na2CO3.
Materials: Distilled water and 1.0 mol dm–3 sodium carbonate solution, Na2CO3 from Activity 6.7
Apparatus: 100 cm3 volumetric flask, dropper, filter funnel, pipette, wash bottle, pipette filler and

100 cm3 beaker
Procedure:

(a) Pour stock solution from
 Activity 6.7 into a beaker

(b) Take out calculated volume of
 solution, V1 cm3 with a pipette

(c) Transfer V1 cm3 of solution
 into a volumetric flask

(f)  Close the volumetric flask and shake
 well by inverting it several times
 until the solution is homogenous

(e) Add distilled water slowly
 with a dropper

(d) Add distilled water until the
 solution level approaches the
 calibration mark

Volumetric
flask

Distilled
water

Beaker

Stock
solution

Beaker

Pipette

Calibration
mark

Meniscus
level of
solution

Dropper

Calibration
mark

Stopper

Stock
solution Calibration

mark

Figure 6.29 Preparation of 0.2 mol dm–3 sodium carbonate solution, Na2CO3 by dilution method

1. Based on Figure 6.29, plan a procedure to prepare a standard
solution of 0.2 mol dm–3 sodium carbonate, Na2CO3 by
dilution method.

2. Include precautionary steps in the process of
solution preparation.

3. Show your procedure to your teacher before carrying out
this activity.

4. Carry out the procedure as planned.
 5. Clean and keep the apparatus at their proper places after

carrying out this activity.

TeaserBrain

TeaserBrain

Why is the pipette not rinsed
with distilled water but rinsed
with 1.0 mol dm–3 sodium
carbonate solution, Na2CO3?

165

Acid, Base and Salt CHAPTER 6
Prepare a complete report after carrying out this activity.

Examples 12 and 13 show samples of calculations involved in the preparation of a standard
solution by dilution.

Discussion:

1. What is the volume of the standard solution of 1.0 mol dm–3 sodium carbonate solution, Na2CO3
needed to prepare 100 cm3 of 0.2 mol dm–3 sodium carbonate solution, Na2CO3?

2. What is the size of pipette needed in this preparation process?
 3. Why is the beaker not suitable to be used in preparing a standard solution by the
  dilution method?
 4. Do you need to remove the last drop of the solution in the pipette? Why?

Figure 6.30 shows 75 cm3 of 2.0 mol dm–3 nitric acid, HNO3 that is diluted to x mol dm–3
when 25 cm3 distilled water is added. Calculate the value of x.

25 cm3 distilled water

75 cm3 of 2.0 mol dm–3

nitric acid, HNO3

Nitric acid, HNO3
x mol dm–3

Before dilution After dilution
Figure 6.30

Solution

M1 = 2.0 mol dm–3 ; V1 = 75 cm3
M2 = x mol dm–3 ; V2 = (75 + 25) cm3
 = 100 cm3

2.0 mol dm–3 × 75 cm3 = x mol dm–3 × 100 cm3 Use the formula M1V1 = M2V2

x mol dm–3  = 2.0 mol dm–3 × 75 cm3

100 cm3

= 1.5 mol dm–3

Then, x = 1.5

Example 12

Determine the volume of 2.0 mol dm–3 hydrochloric acid, HCl needed to be pipetted into a
volumetric flask 250 cm3 to produce 0.2 mol dm–3 hydrochloric acid, HCl.

Solution

M1 = 2.0 mol dm–3 ; V1 = ?
M2 = 0.2 mol dm–3 ; V2 = 250 cm3

2.0 mol dm–3 × V1 = 0.2 mol dm–3 × 250 cm3 Use the formula M1V1 = M2V2

V1 = 0.2 mol dm–3 × 250 cm3

2.0 mol dm–3

= 25 cm3

Example 13

Volume of solution
= Volume of HNO3 + Volume of distilled water

166

Interaction between MatterTHEME 3
Activity 6.9
Solving calculation problems involved in the preparation of a standard

solution by dilution

1. Calculate the volume of 2.0 mol dm–3 sodium carbonate solution, Na2CO3 needed to prepare
50 cm3 of 0.1 mol dm–3 sodium carbonate solution, Na2CO3.

2. What is the molarity of sodium hydroxide solution, NaOH when 30 cm3 distilled water is
added to 50 cm3 of 0.5 mol dm–3 sodium hydroxide solution, NaOH?

3. Calculate the volume of solution produced when 50 cm3 of 1.2 mol dm–3 sodium nitrate
solution, NaNO3 is diluted to 0.5 mol dm–3.

4. When 200 cm3 water is added to 50 cm3 concentrated sulphuric acid, H2SO4, sulphuric
acid, H2SO4 with concentration 0.2 mol dm–3 is produced. Calculate the molarity of the initial
concentration of sulphuric acid, H2SO4.

Yourself
TestTest

6.6

1. What is meant by standard solution?

2. X cm3 of 0.15 mol dm–3 zinc nitrate solution, Zn(NO3)2 is pipetted into a 500 cm3
volumetric flask to produce 500 cm3 of 0.018 mol dm–3 zinc nitrate solution, Zn(NO3)2.
Determine the value of X.

3. Calculate the new molarity of hydrochloric acid, HCl produced if 25 cm3 of 1.5 mol dm–3

hydrochloric acid, HCl is diluted to produce 150 cm3 of hydrochloric acid, HCl.

4. Determine the volume of distilled water needed to add to 50 cm3 of 0.2 mol dm–3 sodium
thiosulphate solution, Na2S2O3 so that a 0.025 mol dm–3 sodium thiosulphate solution, Na2S2O3
is produced.

CT

When stung by a bee, the area that had been stung can be treated
with baking soda. Vinegar, on the other hand, is used to treat the
area that had been stung by a wasp. Why?

Neutralisation6.7

Photograph 6.3 Bee and wasp

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.7.1 State the meaning
 of neutralisation
6.7.2 Determine the

concentration of an
unknown solution through
titration method

6.7.3 Solve numerical problems
involving neutralisation

167

Acid, Base and Salt CHAPTER 6
Activity

Definition of Neutralisation

Neutralisation is a reaction between an acid and an alkali (base) to produce salt and water only.
In the reaction, the salt and water produced are neutral because the acid lose its acidity and the
alkali lose its alkalinity.

Acid + Alkali → Salt + Water

For example, the neutralisation reaction between nitric acid, HNO3 with potassium hydroxide,
KOH to produce potassium nitrate solution, KNO3 and water, H2O.

HNO3(aq) + KOH(aq) → KNO3(aq) + H2O(l)

In neutralisation, the actual reaction that occurs only involves the combination of hydrogen
ions, H+, from the acid and the hydroxide ions, OH– from the alkali to produce water molecules, H2O.
Hence, the ionic equation for the reaction is as follows:

H+(aq) + OH–(aq) → H2O(l)

The following shows how the ionic equations for neutralisation reaction can be obtained.

Chemical equation:

HNO3(aq)          +          KOH(aq)          →          KNO3(aq)          +          H2O(l)

H+(aq) + NO3
–(aq) K+(aq) + OH–(aq) K+(aq) + NO3

–(aq) H2O(l)+ +→

Ions in nitric acid Ions in potassium
hydroxide solution

Ions in potassium
nitrate solution

Water
molecules

Ionic equation:  H+(aq) + OH–(aq) → H2O(l)

K+ and NO3
– are considered as spectator ions that

do not change in the reaction. Thus, these ions are
cancelled out in the equation.

6.10
Write chemical equations and ionic equations for neutralisation reactions

1. Complete and balance the following equations. After that, write the relevant ionic equation.
(a) HCl(aq) + Ba(OH)2(aq) →
(b) H2SO4(aq) + KOH(aq) →
(c) HNO3(aq) + NaOH(aq) →

2. Play the role as a chemistry teacher by explaining your findings in front of your classmates.

CT

168

Interaction between MatterTHEME 3
Applications of Neutralisation in Daily Life

Figure 6.31 shows the application of neutralisation for a variety of uses in daily life.

Neutralisation reaction is also applied in the production of fertilisers such as urea, potassium
sulphate, K2SO4, ammonium nitrate, NH4NO3 and others. For example, urea can be produced
from the neutralisation reaction between ammonia, NH3 and carbon dioxide, CO2. How about
other fertilisers? Try to list out the acids and alkalis involved in the production of that fertilisers.

Activity 6.11
Solving problems on soil fertility using suitable

fertilisers

1. Carry out this activity in groups.
 2. Study the following problem statement:

Apart from treating acidic soil, fertilisers need to be added to soil to replace nutrients
such as nitrogen, potassium and phosphorus that have been absorbed by plants. There is a
variety of fertilisers in the market. Which fertilisers are suitable for plants?

3. Gather information concerning the problem given above.
(a) What type of crops were planted?
(b) What are the type of elements required by the crops?
(c) Identify the fertiliser that is suitable for the crops by considering the percentage of

elements such as nitrogen, phosphorus, and other needs, fertiliser cost and the quantity
needed for the area.

4.  Present your group findings in a multimedia presentation.

STEM CT

Medicine

Weak alkali in the
shampoo neutralises
acid on hair.

AgricultureHair health Dental health

Toothpaste contains a
base that neutralises
lactic acid produced by
bacteria in our mouth.

Milk of magnesia Mg(OH)2
relieves gastric pain by
neutralising the excessive
hydrochloric acid in
the stomach.

Milk of
Magnesia

Shampoo

Slaked lime, Ca(OH)2
which is alkaline, is used
to treat acidic soil.

T
O

O
T
H

P
A

S
T
E

M

e

n

y

e

g

a

r

k

a

n

Figure 6.31 Applications of neutralisation in daily life

Century
Skills21st

169

Acid, Base and Salt CHAPTER 6
Titration Method

Titration method is a quantitative analysis method to determine the volume of acid needed to
completely neutralise a given volume of alkali and vice versa.

In acid-base titration, a solution of known concentration is slowly added from a burette
into a conical flask that contains a volume of alkali of unknown concentration. Titration stops as
soon as the acid-base indicator changes colour. The point in the titration at which the acid-base
indicator changes colour is known as the end point.

Activity 6.12
Gather information on various types of fertilisers

1. Carry out this activity in groups.
 2. Visit the websites or refer to printed materials in the library and resource centre to gather

information about:
(a) Ways to produce urea through the reaction between ammonia and carbon dioxide.

Include the chemical equations involved
(b) Types of ammonium fertilisers available in the market
(c) Calculate the percentage by mass of nitrogen for urea and ammonium fertilisers in the market.

Then, compare and determine the quality of fertiliser based on the percentage of nitrogen
 3. Use suitable graphic organisers to present your group work to your classmates.

Activity 6.13
Aim: To determine the concentration of potassium hydroxide solution, KOH by acid-base titration.
Materials: 1.0 mol dm–3 nitric acid, HNO3, potassium hydroxide, KOH (unknown concentration),

phenolphthalein indicator and distilled water
Apparatus: Burette, 25 cm3 pipette, pipette filler, 250 cm3 conical flask, white tile and retort stand

with clamp
Procedure:

1. Rinse a 25 cm3 pipette with a little potassium hydroxide
solution, KOH. Remove the solution.

2. Pipette exactly 25 cm3 of potassium hydroxide
solution, KOH. Transfer it into a conical flask.

3. Add a few drops of phenolphthalein indicator into the
potassium hydroxide solution, KOH and swirl the flask.

4. Rinse a burette with 1.0 mol dm–3 nitric acid, HNO3.
Then, remove the whole solution.

5. Fill the burette with 1.0 mol dm–3 nitric acid, HNO3
  and clamp the burette onto a retort stand. Record the

initial reading of the burette.
 6. Drip 1.0 mol dm–3 nitric acid, HNO3 slowly into the
  conical flask while swirling it.

CT

Figure 6.32

1.0 mol dm–3

nitric acid, HNO3

White tile

Conical flask

Retort
stand

Burette

Potassium
hydroxide
solution, KOH
+ few drops of
phenolphthalein

170

Interaction between MatterTHEME 3
7. Stop adding 1.0 mol dm–3 nitric acid, HNO3 as soon as the
colour of the solution in the conical flask changes from pink
to colourless. Record the final burette reading.

8. Calculate the rough volume, V cm3 of 1.0 mol dm–3 nitric
acid, HNO3 that is needed for titration.

9. Repeat steps 2 and 3.
10.  Flow 1.0 mol dm–3 nitric acid, HNO3 until (V – 5) cm3 into

the conical flask containing 25 cm3 of potassium hydroxide
solution, KOH. Then, stop the flow of 1.0 mol dm–3 nitric
acid, HNO3.

11.  Subsequently add 1.0 mol dm–3 nitric acid, HNO3, drop by
drop, into the conical flask while swirling the flask.

12. Occasionally, rinse the inner surface of the conical flask with
  distilled water to ensure all the 1.0 mol dm–3 nitric acid, HNO3
  has been titrated into the potassium hydroxide solution, KOH.
13.  Stop the titration as soon as the colour of the solution
  turns colourless.
 14. Record the final burette reading.
 15. Repeat steps 9 – 14 twice.
 16. Record your readings in Table 6.4.
Results:

Table 6.4

Number of titration Rough 1 2 3

Initial burette reading (cm3)

Final burette reading  (cm3)

Volume of nitric acid, HNO3 needed (cm3)

Interpreting data:

1. What is the average volume of nitric acid, HNO3, that is needed to neutralise 25 cm3 of
potassium hydroxide solution, KOH by ignoring the rough volume?

2. Write the ionic equation for the reaction between nitric acid, HNO3 and the potassium
hydroxide solution, KOH.

3. Calculate the number of moles of nitric acid, HNO3, needed in this neutralisation reaction.
 4. Calculate the number of moles of potassium hydroxide solution, KOH needed to react

completely with the number of moles of nitric acid, HNO3 calculated in question 3.
 5. Determine the molarity of potassium hydroxide solution, KOH.
Discussion:

1. Why is a white tile used in this activity?
 2. Why should not we rinse the inside of the conical flask with potassium hydroxide solution, KOH

before beginning the titration?
 3. What is the operational definition for the end point in this activity?

Make sure the eye position
is parallel to the meniscus
level of the solution while
taking a burette reading.

Safety Precaution

Prepare a complete report after carrying out this activity.

Although, the addition of
distilled water to rinse the
inner part of a conical flask
changes the concentration
of the mixture solution, the
number of moles of acid
and alkali reacted remain
unchanged. Thus, the volume
of acid needed to neutralise
alkali is not affected.

Ti spLiteracy

Titration procedure

http://bit.ly/2Bev0Fq

171

Acid, Base and Salt CHAPTER 6
The end point of the neutralisation process can be determined when the acid-base indicator
changes colour. When the end point is achieved, all the hydrogen ions, H+ completely neutralise
all the hydroxide ions, OH– to produce water molecules. Table 6.5 shows the phenolphthalein
indicator and methyl orange in acidic, neutral and alkaline conditions.

Table 6.5 Colours of indicators in acidic, neutral and alkaline conditions

Indicator
Colour in medium

Acidic Neutral Alkaline

Phenolphthalein Colourless Colourless Pink

Methyl orange Red Orange Yellow

Solving Numerical Problems Involving Neutralisation

If a mol acid A is completely neutralised by b mol of alkali B, then the formula
MaVa
MbVb

= a
b  can

be used to solve the calculation related to the neutralisation reaction.
 a mol b mol

a  Acid A  + b  Alkali B  → c  Salt  + d Water

Molarity of acid A = Ma Molarity of alkali B = Mb
 Volume of acid A = Va  Volume of alkali B = Vb

Based on the equation above, the mole ratio of acid A to alkali B is a:b.

20 cm3 of 0.25 mol dm–3 sodium hydroxide solution, NaOH is neutralised with 0.2 mol dm–3
hydrochloric acid, HCl. Calculate the volume of hydrochloric acid, HCl needed for this
neutralisation reaction.

Solution

a = 1 mol b = 1 mol

HCl + NaOH → NaCl + H2O Write this chemical equation and determine the
value of a and b based on the coefficients of this
chemical equation.Ma = 0.2 mol dm–3   ; Va = ?

Mb = 0.25 mol dm–3 ; Vb = 20 cm3

0.2(Va)
0.25(20)  = 1

1  Use the formula
MaVa
MbVb

= a
b

0.2(Va) = 1
1  × (0.25)(20)

Va = 0.25(20)
0.2

= 25 cm3

Volume of hydrochloric acid, HCl that is needed = 25 cm3

Example 14

Further
examples

http://bit.ly/
35UzBuQ

172

Interaction between MatterTHEME 3
4.05 g of zinc oxide, ZnO is needed to complete the neutralisation of 50 cm3 of nitric acid, HNO3.
Calculate the concentration of the acid in mol dm–3.
[Relative atomic mass: H = 1, N = 14, O = 16, Zn = 65]

Solution

a = 2 mol b = 1 mol

2 HNO3  +  ZnO  →  Zn(NO3)2  +  H2O

Number of moles of ZnO, n = 4.05 g
(65 + 16) g mol–1  Convert the given quantity (4.05 g) to

number of moles.

                 RAM Zn RAM O
 = 0.05 mol

Based on the chemical equation,
2.0 mol of HNO3 reacts with 1.0 mol of ZnO
0.1 mol of HNO3 reacts with 0.05 mol of ZnO Based on the mol ratio, determine the

number of moles of HNO3.

Number of moles of HNO3, n = MV
1000

0.1 mol = (M)(50)
1000

M = 2.0 mol dm–3

Molarity of nitric acid, HNO3 = 2.0 mol dm–3

Example 15

Write a balanced chemical equation.

Convert the number of moles
of HNO3 to molarity.

Activity 6.14
Solving numerical problems involving neutralisation

1. 25 cm3 of 0.2 mol dm–3 sodium hydroxide solution, NaOH is titrated with
0.1 mol dm–3 sulphuric acid, H2SO4. What is the volume of sulphuric acid, H2SO4
needed to neutralise sodium hydroxide solution, NaOH?

2. Sulphuric acid, H2SO4, reacts with ammonia solution, NH3 according to the following
  chemical equation:

H2SO4(aq) + 2NH3(aq) → (NH4)2SO4(aq)

It is given that T cm3 of 0.125 mol dm–3 sulphuric acid, H2SO4 exactly neutralises 25 cm3 of
1.0 mol dm–3 ammonia solution, NH3. Determine the total volume of solution in the conical
flask at the end point of titration.

3. 50 cm3 of nitric acid, HNO3 completely neutralises 50 cm3 of 0.25 mol dm–3 calcium
hydroxide, Ca(OH)2. Calculate the molarity of the nitric acid, HNO3.

4. In a titration, 15 cm3 of 0.5 mol dm–3 sulphuric acid, H2SO4 neutralises 20 cm3 of potassium
hydroxide solution, KOH. Calculate the concentration of potassium hydroxide solution, KOH.

CT

173

Acid, Base and Salt CHAPTER 6
Yourself
TestTest

6.7

1. What is the meaning of neutralisation?
 2. State the changes in the methyl orange indicator inside the conical flask containing

potassium hydroxide solution, KOH when it reaches end point.
 3. 50 cm3 of 0.75 mol dm–3 ammonia solution, NH3 is titrated with 1.0 mol dm–3 nitric

acid, HNO3. What is the volume of 1.0 mol dm–3 nitric acid, HNO3 that is needed to
neutralise the ammonia solution, NH3?

4. Calculate the volume of 0.05 mol dm–3 hydrochloric acid, HCl that exactly neutralises
25 cm3 of 0.1 mol dm–3 barium hydroxide solution, Ba(OH)2.

5. Based on the following chemical equation, 20 cm3 monoprotic acid, HX reacts completely
with 10 cm3 of 0.1 mol dm–3 potassium hydroxide solution, KOH.

HX(aq) + KOH(aq) → KX(aq) + H2O(l)

What is the molarity of this acid?

6. A student dissolves hydrogen chloride gas, HCl in water to produce 500 cm3 of acidic
solution. Calculate the molarity of the solution if 6 g of copper(ll) oxide, CuO is used for a
complete reaction with the solution produced.

[Relative atomic mass: O = 16, Cu = 64]

Salts, Crystals and Their Uses in Daily Life6.8

Definition of Salt

Salt is an ionic compound. Salt can be produced from the neutralisation reaction between acid
and alkali (base).

Figure 6.33 Salt and egg shell

The common table salt used in cooking is made up of sodium
ions, Na+ and chloride ions, Cl–. The egg shell is made up of
calcium ions, Ca2+ and carbonate ions, CO3

2–. Is calcium carbonate
a type of salt too?

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.8.1 State the meaning of salt
6.8.2 Characterise the physical

properties of salt crystals
6.8.3 Give examples of salt and

their uses in daily life

174

Interaction between MatterTHEME 3
Reaction between acid and alkali

H Cl (aq) + Na OH(aq) → NaCl(aq) + H2O(l)

Anion from acid

Sodium
chloride saltCation from base

Can salt only be produced from acid and base reaction? Look at the following chemical equations
to find out further on the salt production concept.

Reaction between acid and reactive metals

2H Cl (aq) + Zn (s) → ZnCl2(aq) + H2(g)

Cation from metal
Zinc chloride
salt

Anion from acid

Reaction between acid and metal carbonate

2H Cl (aq) + Ca CO3(s) → CaCl2(aq) + CO2(g) + H2O(l)

Cation from metal carbonate

Anion from acid

Calcium
chloride salt

Reaction between acid and aqueous ammonia

H Cl (aq) + NH3 (aq) → NH4Cl(aq)

Cation from aqueous ammonia

Anion from acid

Ammonium
chloride salt

Based on the chemical equations above, salt can be defined as follow:
Salt is an ionic compound formed when the hydrogen ion, H+ from the acid is replaced with
the metal ion or the ammonium ion, NH4

+.

Activity 6.15
Gathering and interpreting information on the existence of salts that

exist naturally

1. Carry out this activity in groups.
 2. Gather information on salts that exist naturally. Your information should include the following:

(a) Name of the salts
(b) Source or location of the salts
(c) Relevant photograph of the salts

3. Interpret the information gathered with suitable graphic organisers.
 4. Present the information in front of your class.

175

Acid, Base and Salt CHAPTER 6
Figure 6.34 Physical properties of salt crystal

Examples of Salts and Their Uses

Besides sodium chloride salt, NaCl that we use everyday, there are more salts that exist naturally
as minerals in the Earth’s crust. These salts have their own uses in various fields.

Physical Properties of Salt Crystals

All salt crystals have specific features. Can you state the physical properties of a salt crystal?
Activity 6.16 can assist you in showing characteristics of a salt crystal.

Activity 6.16
Carrying out a crystal growth activity

1. Carry out this activity in pairs.
 2. Watch the video clip on the steps taken to produce a large

crystal through the growth of crystal.
 3. Discuss with your partner on the important procedures in

producing copper(II) sulphate crystal, CuSO4.
 4. Carry out the crystal growth activity of copper(II)sulphate, CuSO4 in a time frame of two

weeks with your teacher̕s permission.
 5. Dry the crystal produced and observe the crystal under a microscope.
 6. Record the physical properties of the crystal and sketch its shape in your notebook.

A crystal has specific properties because the particles in
the crystal are arranged in compact and orderly manner
according to a specific design arrangement.

has flat surface, straight
sides and sharp vertices

has a specific geometrical
shape such as cube, cuboid,
rhombus and prism

same crystals of different
sizes still have the same
geometrical shapes

different crystals have
different geometrical shapes

has a fixed angle between
two adjacent surfaces

Crystal growth

http://bit.ly/2IOG7ZY

176

Interaction between MatterTHEME 3
Agriculture

Activity 6.17

Activity 6.18

Making a multimedia presentation on the uses of various salts

1. Carry out this activity in groups.
 2. Surf the Internet or refer to printed materials at the library to gather information on the

various uses of salt in the following fields:

Agriculture

Medicine

Preservation

Food preparation

3. Interpret the information obtained and present your group’s work using multimedia presentations.

Debating the effects of salt on humans

1. Read and understand the following extract:

Table salt, Himalayan salt and bamboo salt are among the salts found on Earth. Humans need
salt to maintain the fluid balance in their body, prevent muscle cramps and others. However,
a high salt content will cause high blood pressure, stroke, kidney failure and other diseases.

2. Gather information on the effects of salt on humans.
 3. Debate the effects of salt on human health.

Calcium sulphate, CaSO4 as plaster of Paris to support
broken bones while potassium manganate(VII) is used
as antiseptic to treat wounds.

Food preparation

Medicine

Preservation

Figure 6.35 Various uses of salt in daily life

Sodium chloride, NaCl is used as flavour.
Sodium bicarbonate, NaHCO3 is used for raising dough.

Sodium benzoate, C6H5COONa is used to preserve
chilli sauce, tomato sauce and oyster sauce. Sodium
nitrate, NaNO3 is used to preserve processed meat
such as sausages.

Ammonium nitrate, NH4NO3 as fertiliser while
iron(II) sulphate, FeSO4 is used in pesticides to kill
pests and grass.

Antiseptic

177

Acid, Base and Salt CHAPTER 6
The solid as shown in Photograph 6.4
is the Himalayan salt. Does the
Himalayan salt dissolve in water? Is
it true that all types of salt dissolve
in water?

Solubility of Salt in Water

Salt is an ionic compound. The solubility of various salts in
water is investigated in Experiment 6.5.

Aim: Investigate the solubility of various salts in water.
Problem statement: Do all salts dissolve in water?
Hypothesis: Some salts dissolve in water, some salts do not.
Variables:

(a) Manipulated : Types of nitrate, sulphate, chloride, carbonate and ammonium salt
(b) Responding : Solubility of salt in water
(c) Fixed : Volume and temperature of water, mass of salt
Procedure:

ON
OFF g

Salt

Electronic
balance

Distilled water Stir

Glass rod

Salt

Figure 6.36 Apparatus set-up to investigate the solubility of salt
 1. Based on Figure 6.36, list out the apparatus and materials/substances used in this experiment.

Experiment 6.5

Yourself
TestTest

6.8

1. Define the meaning of salt.
 2. List out the physical properties of a salt crystal.
 3. Give examples of salts and their uses in the following fields:

(a) Agriculture (b) Medicine

Preparation of Salts6.9

Photograph 6.4
Himalayan salt

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.9.1 Test the solubility of salt in

water and classify them into
soluble and insoluble salts
through experiment

6.9.2 Describe the preparation of a
soluble salt through activity

6.9.3 Describe the preparation
of an insoluble salt
through activity

6.9.4 Construct an ionic equation
using the continuous
variation method
through experiment

178

Interaction between MatterTHEME 3
Prepare a complete report after carrying out this experiment.

Soluble salts are salts that dissolve in water at room temperature and non-soluble salts
are salts that do not dissolve at room temperature. Table 6.6 shows the types of salts and their
solubilities in water.

Table 6.6 Solubility of salts in water
Types of salts Soluble in water Insoluble in water

Nitrate salt (NO3
–) All nitrate salts None

Sulphate salt (SO4
2–) All sulphate salts except Lead(II) sulphate, PbSO4

Barium sulphate, BaSO4
Calcium sulphate, CaSO4

Chloride salt (Cl–) All chloride salts  except Mercury(I) chloride, Hg2Cl2
Lead(II) chloride, PbCl2
Silver chloride, AgCl

Carbonate salt (CO3
2–) Sodium carbonate, Na2CO3

Potassium carbonate, K2CO3
Ammonium carbonate, (NH4)2CO3

Other carbonate salts

Ammonium, sodium and
potassium salts

All ammonium, sodium and
potassium salts

None

Mnemonics:
All NO ASaP salts dissolve
in water.
PBC sulphates and HPA
chlorides do not dissolve
in water.

Ti spLiteracy

2. Plan the experiment procedure with the members of your group.
 3. Prepare an appropriate table to record your observation.
 4. Carry out the experiment with your teacher̕s permission.
 5. Record the observation obtained in the table you have prepared.
Interpreting data:

1. Based on the results of the experiment, list out:
(a) Nitrate, sulphate, chloride, carbonate and ammonium salts that dissolve in water
(b) Sulphate, chloride and carbonate salts that do not dissolve in water

2. Formulate and classify the types of salt that dissolve or do not dissolve in water in an
appropriate table.

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Sodium

PotassiumAmmonium

NO ASaP

NO3
–

H ← Hg2Cl2
P ← PbCl2
A ← AgCl

P ← PbSO4
B ← BaSO4
C ← CaSO4

Do not taste the salts. There
are salts that are poisonous.

ChemistryChemistry

The empirical formula for
mercury(I) chloride is HgCl.
Because mercury atoms, Hg
tend to form Hg-Hg bonds,
therefore the chemical
formula for mercury(I)
chloride is Hg2Cl2.

Bond between Hg-Hg

Cl ClHg Hg

179

Acid, Base and Salt CHAPTER 6
Figure 6.37 Special properties of lead(II) chloride, PbCl2 and lead(II) iodide, PbI2

Preparation of Soluble Salts

The method to prepare salts depends on the solubility of the salt in water and the type of salt
required. Figure 6.38 shows the various methods for the preparation of soluble and insoluble salts.

All ammonium salts,
sodium salts and
potassium salts

Figure 6.38 Methods for preparing soluble and insoluble salts

Neutralisation reaction
between acid and alkali

Not ammonium salt,
sodium salt or potassium salt

Reaction between:
•	 Acid	+	Reactive	metal
•	 Acid	+	Metal	oxide
•	 Acid	+	Metal	carbonate

Double decomposition reaction
(precipitation reaction)

Salt

Soluble salt Insoluble salt

Acid

Alkali Acid

Excess of metal
solid/ metal oxide/
metal carbonate

Lead(II) chloride, PbCl2 and lead(II) iodide, PbI2 are two
types of salts that are special. These salts are initially insoluble in
water, but can be dissolved in hot water to produce a colourless
solution. Solids are reformed when water is cooled.

Heat
White solid of lead(II)
chloride, PbCl2

White solid
dissolves in hot
water to form a
 colourless solution

White solid is
formed again when
water is cooled

Heat
Yellow solid of lead(II)
iodide, PbI2

Yellow solid
dissolves in hot
water to form a
colourless solution

Yellow solid is
formed again when
water is cooled

Precipitate of
insoluble salt

Salt
solution A Soluble salt

solution

Salt
solution B

TeaserBrain

Are lead(II) chloride, PbCl2
and lead(II) iodide, PbI2
classified as soluble or
insoluble salts? Why?

TeaserBrain

180

Interaction between MatterTHEME 3
Preparation of Soluble Ammonium, Sodium and Potassium Salts

Activity 6.19
Aim: To prepare soluble salts through a neutralisation reaction between an acid and an alkali.
Materials: 2.0 mol dm–3 hydrochloric acid, HCl, 2.0 mol dm–3 potassium hydroxide solution, KOH,

phenolphthalein indicator, filter papers and distilled water
Apparatus: 250 cm3 beaker, glass rod, filter funnel, retort stand with clamp, 25 cm3 pipette,

pipette filler, burette, evaporating dish, Bunsen burner, pipeclay triangle, conical flask,
tripod stand, white tile and wash bottle

Procedure:

Potassium hydroxide solution,
KOH + phenolphtalein

Hydrochloric
acid, HCl

Potassium chloride
solution, KCl

Potassium chloride
solution, KClV cm3 of

hydrochloric
acid, HCl

Heat

Pipeclay
triangle

Wash bottle

Filter
papers

Dry potassium
chloride crystals, KCl

Potassium
chloride
crystal, KCl

Saturated
potassium
chloride
solution, KCl Distilled

water

Potassium
chloride
crystals, KCl

Figure 6.39 Apparatus set-up to obtain potassium chloride crystals, KCl

1. Rinse a 25 cm3 pipette with a small amount of 2.0 mol dm–3 potassium hydroxide, KOH. Then,
discard the solution.

2. Pipette accurately 25 cm3 of 2.0 mol dm–3 potassium hydroxide solution, KOH and transfer into
a conical flask.

3. Add a few drops of phenolphthalein indicator and swirl the flask.
 4. Rinse a burette with 2.0 mol dm–3 hydrochloric acid, HCl. Then, discard the solution.
 5. Fill the burette with 2.0 mol dm–3 hydrochloric acid, HCl and clamp the burette to the

retort stand. Record the initial reading of the burette.

181

Acid, Base and Salt CHAPTER 6
Preparation of Soluble Salts which are not Ammonium, Sodium and Potassium Salts

6. Add acid into the conical flask slowly while swirling it.
 7. Continue adding acid until the colour of the solution in the

conical flask changes from pink to colourless.
 8. Record the final reading of the burette. Then, determine

the volume of 2.0 mol dm–3 hydrochloric acid, HCl required
to neutralise 25 cm3 of 2.0 mol dm–3 potassium hydroxide
solution, KOH (assuming the acid volume is V cm3).

9. Refill a new 25 cm3 of 2.0 mol dm–3 potassium hydroxide
solution, KOH into a conical flask without phenolphthalein
indicator.

10. Add V cm3 of 2.0 mol dm–3 hydrochloric acid, HCl from a
burette into the conical flask and swirl the mixture to ensure
the mixture is even.

11. Pour the content of the conical flask into an evaporating dish.
 12. Heat the solution slowly to evaporate the water so that a

saturated solution is obtained.
 13. Let the saturated salt solution cool down to allow crystallisation to occur.
 14. Filter the contents of the evaporating dish to obtain potassium chloride crystals, KCl.
 15. Rinse the crystals with a little amount of distilled water.
 16. Dry the salt crystals by pressing them between two pieces of filter papers.

Discussion:

1. Why is phenolphthalein indicator needed in titration?
 2. Why should not phenolphthalein indicator be added to V cm3 of hydrochloric acid, HCl to 25 cm3

of potassium hydroxide solution, KOH?
 3. Explain why the resulting crystals can only be rinsed with a little amount of distilled water.
 4. Write a balanced chemical equation for this neutralisation reaction.
 5. Give two other types of soluble salts that can be prepared by this method.

To know whether the salt
is saturated or not, dip the
glass rod into the solution
and then remove the glass
rod. If crystals are produced,
a saturated solution has
been obtained.

Safety Precaution

Glass rod

Salt
crystal

Prepare a complete report after carrying out this activity.

Aim: To prepare a soluble salt based on the reaction between an acid and a metal oxide.
Materials: 2.0 mol dm–3 nitric acid, HNO3, copper(II) oxide powder, CuO, filter papers and

distilled water
Apparatus: 250 cm3 beaker, spatula, glass rod, filter funnel, evaporating dish, Bunsen burner,

pipeclay triangle, conical flask, tripod stand, wash bottle, 20 cm3 measuring cylinder
and retort stand with clamp

Activity 6.20

182

Interaction between MatterTHEME 3
Procedure:

Heat

Pipeclay
triangle

Evaporating
dish

Saturated
solution

Distilled
water

Wash
bottle

Filter
papers

Salt crystalsSalt crystals

Salt
solution

Glass rod

20 cm3

of nitric
acid, HNO3

Spatula
Excess of
copper(II)
oxide, CuO

Filter funnel

Filter paper

Excess of
copper(II) oxide
powder, CuO

Copper(II)
nitrate, Cu(NO3)2

Dry salt crystals

Figure 6.40 Apparatus set-up to obtain copper(II) nitrate crystal, Cu(NO3)2

1. Pour 20 cm3 of 2.0 mol dm–3 nitric acid, HNO3 into a beaker. Heat the acid using medium heat.
 2.  Add copper(II) oxide powder, CuO gradually into the acid using a spatula. Stir the mixture

with a glass rod.
 3. Continue adding copper(II) oxide, CuO until it is no longer dissolved.
 4. Filter the excess copper(II) oxide powder, CuO from the mixture.
 5. Pour the filtrate into an evaporating dish and heat the filtrate till a saturated salt solution

is obtained.
 6. Let the resulting saturated solution cool until salt crystals are formed.
 7. Filter the content of the evaporating dish to obtain the salt crystals. Rinse the crystals with a

little amount of distilled water.
 8. Dry the salt crystals by pressing them between two pieces of filter papers.

Discussion:

1. Why is copper(II) oxide, CuO added in excess to the solution?
 2. The filtration is done twice in this activity. Explain why.
 3. Write a chemical equation for the reaction between nitric acid, HNO3 and copper(II)

oxide, CuO.
 4. Is the reaction between nitric acid, HNO3 and copper(II) oxide, CuO also considered a

neutralisation reaction? Give a reason.

Prepare a complete report after carrying out this activity.

183

Acid, Base and Salt CHAPTER 6
Activity 6.21
Aim: To prepare a soluble salt based on the reaction between an acid and a reactive metal.
Materials: 2.0 mol dm–3 sulphuric acid, H2SO4, zinc powder, Zn, filter paper and distilled water
Apparatus: 250 cm3 beaker, spatula, glass rod, filter funnel, evaporating dish, Bunsen burner,

pipeclay triangle, conical flask, tripod stand, wash bottle and retort stand with clamp

Procedure:

1. In pair, study Activity 6.20 on pages 182 and 183. Then, plan the procedures for the lab activity
to prepare soluble salts of zinc sulphate, ZnSO4 based on the reaction between an acid and

a metal.
 2. Discuss with your teacher if you encounter any problem when planning the procedures.

Discussion:

1. Does zinc powder, Zn, have to be added in excess to the sulphuric acid, H2SO4? Why?
 2. Write a chemical equation for the reaction between sulphuric acid, H2SO4 and the metal

zinc, Zn.
 3. Copper powder is not suitable to prepare copper(II) sulphate salt, CuSO4 by using the method

in this activity. Give the reason why.

Activity 6.22
Aim: To prepare a soluble salt based on the reaction between an acid and a metal carbonate.

Procedure:

1. In groups, determine a soluble salt that needs to be prepared.
 2. Based on the chosen soluble salt, determine the materials and apparatus needed for this activity.
 3. Plan and carry out the activity to prepare the soluble salt based on the reaction between an acid

and an insoluble metal carbonate.

Discussion:

1. Name the gas that is produced.
 2. Describe the chemical test for the gas released.
 3. Write the chemical equation involved.

Purification of Soluble Salts by the Recrystallisation Method

The soluble salt produced might contain impurities during preparation. Therefore, the soluble salt
can be purified by the recrystallisation method. Carry out Activity 6.23 to find out how to purify
a soluble salt.

Prepare a complete report after carrying out this activity.

Prepare a complete report after carrying out this activity.

184

Interaction between MatterTHEME 3
Activity 6.23
Aim: To prepare a pure soluble salt through the recrystallisation method.
Materials: Copper(II) sulphate crystals, CuSO4, filter papers and distilled water
Apparatus: 250 cm3 beaker, spatula, glass rod, filter funnel, evaporating dish, Bunsen burner,

wire gauze, pipeclay triangle, conical flask, tripod stand, wash bottle and retort stand
with clamp

Procedure:

Saturated solution

Distilled water

Salt crystals
Salt crystals

Insoluble
impurities

Filtrate

Copper(II)
sulphate
crystals, CuSO4

Heat

Pipeclay
triangle

Evaporating
dish

Salt solution

Glass rod

Filter funnel

Filter
paper

Dry salt crystals

Glass rod

Distilled
water

Heat

Filter
papers

Figure 6.41 Apparatus set-up to purify copper(II) sulphate salt, CuSO4

1. Put the copper(II) sulphate crystals, CuSO4 into a beaker.
 2. Add distilled water gradually while stirring. Heat the

solution to speed up the process of dissolving the salt.
 3. Filter the hot salt solution to remove insoluble impurities.
 4. Then, pour the filtrate into an evaporating dish and heat the

filtrate until a saturated salt solution is obtained.
 5. Let the saturated solution cool until salt crystals are formed.
 6. Filter the contents of the evaporating dish to get the salt crystals. Rinse the crystals with a little

amount of distilled water.
 7. Dry the salt crystals by pressing them between two pieces of filter papers.

Make sure the distilled water
added is just enough to
dissolve all the crystals.

Safety Precaution

185

Acid, Base and Salt CHAPTER 6
Preparation of Insoluble Salts

Insoluble salts can be prepared through double decomposition reaction. In this process, two salt
solutions that contain insoluble salt ions are needed.

Preparing Insoluble Salts by Double Decomposition Reaction

Discussion:

1. What is the purpose of rinsing the crystals formed with distilled water?
 2. State the method used to increase the size of the crystals formed.
 3. Can recrystallisation be used to purify insoluble salts? Why?

Activity 6.24
Aim: To prepare an insoluble salt by double decomposition reaction.
Materials:  2.0 mol dm–3 sodium sulphate solution, Na2SO4, 2.0 mol dm–3 barium chloride

solution, BaCl2, filter papers and distilled water
Apparatus: 250 cm3 beaker, measuring cylinder, glass rod, filter funnel, evaporating dish, conical

flask and wash bottle
Procedure:

Dry insoluble salts

Precipitate of
barium sulphate,
BaSO4

Barium chloride
solution, BaCl2

Sodium sulphate
solution, Na2SO4

Sodium chloride
solution, NaCl

Sodium chloride
solution, NaCl

Precipitate of barium
sulphate, BaSO4

Glass rod

Filter funnel

Filter papers

Filter paper

Precipitate of
barium sulphate,
BaSO4

Figure 6.42 Apparatus set-up in the preparation of insoluble salt

1. Based on Figure 6.42, plan the activity with your group members to prepare the insoluble salt
of barium sulphate, BaSO4.

2. Discuss with your teacher if you encounter any problems while planning the procedure.
 3. Carry out the activity with your teacher̕s permission.

Prepare a complete report after carrying out the activity.

186

Interaction between MatterTHEME 3
In the double decomposition reaction, the ions in both aqueous solutions exchange with each
other to form a new aqueous solution and a precipitate. The ionic equation for the formation of
barium sulphate, BaSO4 can be derived from the balanced chemical equations as shown below:

Discussion:

1. Write a balanced chemical equation for the preparation of barium sulphate salt, BaSO4.
 2. Write an ionic equation for the preparation of barium sulphate salt, BaSO4.
 3. Why must the filtered barium sulphate salt, BaSO4 precipitate rinsed with distilled water?
 4. In your opinion, is it suitable to prepare barium sulphate salt, BaSO4 based on the reaction

between sulphuric acid, H2SO4 and barium carbonate, BaCO3? Explain your answer.
 5. Name two other salts that can be prepared by the double decomposition reaction. Then,

suggest suitable aqueous solutions for the preparation of the salts mentioned.

Chemical equation:

Ba2+(aq) + 2Cl–(aq) 2Na+(aq) + SO4
2–(aq) BaSO4(s) 2Na+(aq) + 2Cl–(aq)+

+

+

+

→

→BaCl2(aq) Na2SO4(aq) BaSO4(s) 2NaCl(aq)

Ions in barium chloride Ions in sodium sulphate Precipitate Ions in sodium chloride

Ionic equation: Ba2+(aq) + SO4

2–(aq) → BaSO4(s)

The Na+ ion and Cl– ion are spectator ions which
do not take part in the reaction. Thus, these ions
are cancelled out in the equation.

Activity 6.25
Writing the ionic equation for the formation of insoluble salts

1. Write the ionic equation for the following reactions:
(a) The reaction between silver nitrate, AgNO3 and magnesium chloride, MgCl2
(b) Mixing potassium chromate(VI), K2CrO4 with lead(II) nitrate, Pb(NO3)2
(c) Copper(II) chloride solution, CuCl2 is added to sodium carbonate solution, Na2CO3

Prepare a complete report after carrying out this activity.

187

Acid, Base and Salt CHAPTER 6
Construction of Ionic Equations through the Continuous Variation Method

The continuous variation method is used to construct the ionic equation for the formation of
insoluble salts. In this method, the volume of one solution, A is fixed, while solution B is added to
the solution A by increasing the volume as shown in Figure 6.43.

Solution B

Solution A with fixed volume

8 cm37 cm36 cm35 cm34 cm3



3 cm32 cm31 cm3

Figure 6.43 Continuous variation method
The height of the precipitate formed increases gradually for the first few test tubes and then

becomes constant as shown in Figure 6.44.

The first test tube that achieves
the maximum height of the
precipitate indicates that all
reactants has completely reacted
with one another.

Precipitate

Figure 6.44 Changes of the height of the precipitate

Experiment 6.6

Aim: To construct an ionic equation for the formation of lead(II) iodide.
Problem statement: How to construct an ionic equation for the formation of lead(II) iodide?
Hypothesis: As the volume of potassium iodide solution, KI added to lead(II) nitrate

solution, Pb(NO3)2 increases, the height of the precipitate will increase and
then remain constant.

Variables:

(a) Manipulated : Volume of potassium iodide solution, KI
(b) Responding : Height of the precipitate
(c) Fixed :  Volume and concentration of lead(II) nitrate solution, Pb(NO3)2, concentration

of potassium iodide solution, KI
Materials: 0.5 mol dm–3 lead(II) nitrate solution, Pb(NO3)2, 0.5 mol dm–3 potassium iodide

solution, KI and distilled water
Apparatus: Test tubes of the same size, glass rod, test tube rack, burette, retort stand with clamp

and ruler

186

Interaction between MatterTHEME 3
Procedure:

1. Label eight test tubes from 1 to 8 and place all the
test tubes in a test tube rack.

2. Using a burette, fill each test tube with 5 cm3 of
0.5 mol dm-3 lead(II) nitrate solution, Pb(NO3)2.

3. Using a second burette, add 0.5 mol dm-3 potassium iodide solution, KI into each test tube
according to the volume stated in Table 6.7.

4. Place a glass rod into the test tube. Swirl the glass rod with both palms to ensure even mixing
of the two solutions.

5. Slowly remove the glass rod. Rinse the precipitate that is stuck to the glass rod and the walls of
the test tubes with distilled water.

6. Repeat steps 4 and 5 for the rest of the test tubes.
 7. Leave the test tubes to stand for 30 minutes for the precipitate to settle to the bottom.
 8. Record the colour of the precipitate formed and the solution on top of the precipitate.
 9. Measure and record the height of the precipitate in each test tube.
Results:

Table 6.7

Test tube 1 2 3 4 5 6 7 8

Volume of lead(II) nitrate solution, Pb(NO
3

)
2

(cm
3

) 5 5 5 5 5 5 5 5

Volume of potassium iodide solution, KI (cm
3

) 1 2 3 4 5 6 7 8

Height of precipitate (cm)

Colour of the solution on top of the precipitate

Interpreting data:

1. Plot a graph of the height of the precipitate against the volume of potassium iodide, KI.
 2. From the graph, determine the volume of the potassium iodide solution, KI that completely

reacts with 5 cm3 of lead(II) nitrate solution, Pb(NO3)2.
 3. Calculate the number of moles for:

(a) Lead(II) ions, Pb2+ in 5 cm3 of 0.5 mol dm–3 lead(II) nitrate solution, Pb(NO3)2
(b) Iodide ions, I– that reacts with 5 cm3 of 0.5 mol dm–3 lead(II) nitrate solution, Pb(NO3)2

4. Determine the number of moles of iodide ion, I– that reacts completely with 1 mol of lead(II)
ion, Pb2+.

5. Based on your answer in questions 3 and 4, construct an ionic equation for the formation of
the lead(II) iodide precipitate, PbI2.

Conclusion:

Is the hypothesis acceptable? What is the conclusion of the experiment?
Discussion:

1. Why should the test tubes be of the same size?
 2. Explain why the height of the precipitate increases gradually and then remains constant.

Make sure all the test tubes
used are of the same size.

Safety Precaution

Prepare a complete report after carrying out this experiment.

189

Acid, Base and Salt CHAPTER 6
In the continuous variation method, fixing the volume of
lead(II) nitrate solution, Pb(NO3)2 while manipulating the volume
of potassium iodide, KI is to determine the mole ratio of lead(II)
ions, Pb2+ that will react completely with the iodide ions, I–. If
x mol of lead(II) ions, Pb2+ reacts with y mole of iodide ions, I–,
then the empirical formula of the insoluble salt is PbxIy.

x(ion Pb2+) + y(ion I–) → PbxIy

Yourself
TestTest

6.9

1. Classify the following into soluble and insoluble salts.

NaNO3 BaSO4 CaCO3 NaCl
Pb(NO3)2 MgSO4 K2CO3 AgCl
(NH4)2SO4 PbI2 BaCrO4 ZnCl2

2. Suggest suitable aqueous solutions for the preparation of calcium sulphate salt, CaSO4.
Then, write an ionic equation for the formation of the salt.

3. Using a diagram, show how zinc nitrate crystals, Zn(NO3)2 can be prepared. In your
diagram, include the reagents that are needed.

Effect of Heat on Salts6.10

What is the gas released? Limewater turns cloudy. The
salt is a carbonate salt because
carbon dioxide is released.

Figure 6.45 Carbon dioxide gas turns limewater cloudy

TeaserBrain

TeaserBrain

If 2 moles of silver ions,
Ag+ reacts with 1 mole of
carbonate ions, CO3

2–, can
you write the ionic equation
for the formation of silver
carbonate salt?

Based on the conversation in Figure 6.45, can you identify the
anion based on the gas released?

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.10.1	 Describe	briefly

chemical tests to
identify	gases

6.10.2	 Investigate	the	effects
of heat on salts
through	experiment

186

Interaction between MatterTHEME 3
Gas Tests

The process to identify a gas can be carried out by the gas test in Activity 6.26.

Activity 6.26
Aim:  Identifying the gases released.
Materials: Solid potassium chlorate(V), KClO3, dilute sulphuric acid, H2SO4, zinc powder, Zn,
 solid zinc carbonate, ZnCO3, dilute sodium hydroxide solution, NaOH, solid ammonium

chloride, NH4Cl, solid manganese(IV) oxide, MnO2, concentrated hydrochloric acid, HCl,
solid sodium chloride, NaCl, concentrated sulphuric acid, H2SO4, concentrated

ammonia solution, NH3, solid sodium sulphite, Na2SO3, dilute hydrochloric acid, HCl,
acidified potassium manganate(VII) solution, KMnO4, solid lead(II) nitrate, Pb(NO3)2,
red litmus paper, blue litmus paper and limewater

Apparatus: Test tubes, test tube holder, wooden splinter, rubber stopper with delivery tube, glass
rod, spatula, tongs, Bunsen burner and 10 cm3 measuring cylinder

Procedure:

Carry out the test for gases and record your observations.

Table 6.8

Gas test Observation Inference

A: Test for oxygen gas, O2

1. Put two spatulas of solid
potassium chlorate(V), KClO3 into
a test tube.

2. Heat the solid with high heat.
3. Insert a glowing wooden splinter

into the test tube.

B:  Test for hydrogen gas, H2

1. Put some a few pieces of zinc
powder, Zn into a test tube.

2. Add 4 cm3 of dilute sulphuric
acid, H2SO4 into the test tube.

3. Place a lighted wooden splinter
near the mouth of the test tube.

C: Test for carbon dioxide gas, CO2

1. Put a spatula of solid zinc
carbonate, ZnCO3 into a test tube.

2. Heat the solid with high heat.
3. Flow the gas produced into

limewater.

This activity has to be carried
out in the fume chamber.

Glowing
wooden
splinter

KClO3

Heat

Lighted
wooden
splinter

Zn

H2SO4

Heat

ZnCO3

Limewater

191

Acid, Base and Salt CHAPTER 6
Gas test Observation Inference

D: Test for ammonia gas, NH3

1. Put a spatula of solid ammonium
chloride, NH4Cl into a test tube.

2. Add 4 cm3 of dilute sodium hydroxide
solution, NaOH into the test tube.

3. Heat the mixture slowly.
4. Then, place a piece of moist red litmus

paper to the mouth of the test tube.

E: Test for chlorine gas, Cl2

1. Put a spatula of powdered
manganate(IV) oxide, MnO2 into a
test tube.

2. Carefully add 2 cm3 of concentrated
hydrochloric acid, HCl.

3. Heat the mixture slowly.
4. Then, place a piece of moist blue litmus

paper to the mouth of the test tube.

F:  Test for hydrogen chloride gas, HCl
1. Put a spatula of solid sodium chloride,

NaCl into a test tube.
2. Add 2 cm3 of concentrated sulphuric

acid, H2SO4 carefully.
3. Heat the mixture slowly.
4. Dip a glass rod into concentrated

ammonia solution, NH3.
5. Then, hold the dipped glass rod to

the mouth of the test tube.

G: Test for sulphur dioxide gas, SO2

1. Put a spatula of solid
sodium sulphite, Na2SO3
into a test tube.

2. Add 4 cm3 of dilute
hydrochloric acid, HCl.

3. Heat the mixture slowly.
4. Flow the gas released

into acidified potassium
manganate(VII) solution, KMnO4.

Heat

Moist blue
litmus paper

HCl

MnO2

Heat

Glass rod with
concentrated
ammonia
solution, NH3

H2SO4

NaCl

Heat

Na2SO3

Acidified
potassium
manganate(VII)
solution, KMnO4

HCl

Heat

Moist red
litmus paper

NaOH

NH4Cl

Note: Acidified potassium manganate(VII) solution, KMnO4
can be replaced with acidified potassium dichromate(VI)
solution, K2Cr2O7.

186

Interaction between MatterTHEME 3
Gas test Observation Inference

H:  Test for nitrogen dioxide gas, NO2

1. Put a spatula of solid lead(II)
nitrate, Pb(NO3)2  into a test tube.

2. Heat the mixture with high heat.
3. Then, place a piece of moist blue

litmus paper to the mouth of the
test tube. Heat

Moist blue
litmus paper

Pb(NO3)2

Interpreting data:

1. Based on the observations, write the corresponding inference.
 2. Why should the litmus paper be moistened before testing for the gases released?
 3. Copy and complete Table 6.9 to summarise the method used for gas test.

Table 6.9

Gas
Chemical tests

Method Observation

Oxygen gas, O2 Place a glowing wooden splinter
into a test tube filled with the gas.

The glowing wooden splinter
rekindles.

Hydrogen gas, H2

Carbon dioxide gas, CO2

Ammonia gas, NH3

Chlorine gas, Cl2

Hydrogen chloride gas, HCl

Sulphur dioxide gas, SO2

Nitrogen dioxide gas, NO2

Discussion:

1. What is the expected observation if a glass rod that is dipped into concentrated hydrochloric
acid, HCl, is brought closer to the gas released in test D?

2. Name the white fumes formed in test F.
 3. The gas released in test G is acidic. Predict the observation when a moist litmus paper is used.

Effect of Heat

Most salts decompose when heated. By comparing the colour of the salt and the residue left
behind and the gas released, we can identify the cation and anion that might be present in the salt.
Experiment 6.7 investigates the action of heat on carbonate salt and nitrate salt.

Prepare a complete report after carrying out this activity.

193

Acid, Base and Salt CHAPTER 6
Experiment 6.7

Aim: To investigate the action of heat on carbonate salts.
Problem statement: Do all carbonate salts decompose when heated to produce carbon
 dioxide gas?
Hypothesis: All carbonate salts decompose when heated to produce carbon dioxide gas.
Variables:

(a) Manipulated : Types of carbonate salts
(b) Responding : Products of decomposed carbonate salts
(c) Fixed : Two spatulas of carbonate salts
Materials: Solid sodium carbonate, Na2CO3, solid calcium carbonate, CaCO3, solid zinc

carbonate, ZnCO3, solid lead(II) carbonate, PbCO3, solid copper(II) carbonate, CuCO3
and limewater

Apparatus: Test tubes, boiling tubes, test tube holder, Bunsen burner and rubber stopper with
delivery tube

Procedure:

1. Place two spatulas of solid sodium carbonate, Na2CO3

into a dry boiling tube. Observe the colour of salt and
record the observation.

2. Connect the rubber stopper with the delivery tube to the
mouth of the boiling tube. Ensure that the other end of
the delivery tube is placed into the limewater as shown

in Figure 6.46.
 3. Heat the carbonate salt with high heat.
 4. Observe the changes that occur in the limewater and the colour of the residue in the boiling

tube when it is hot and when it is cool. Record the observation.
 5. Repeat steps 1 to 4 using other carbonate salts to replace sodium carbonate salt, Na2CO3.
Results:

Table 6.10

Carbonate salt Colour of the salt
before heating

Colour of the residue Effect on
limewaterWhen hot When cool

Sodium carbonate, Na2CO3

Calcium carbonate, CaCO3

Zinc carbonate, ZnCO3

Lead(II) carbonate, PbCO3

Copper(II) carbonate, CuCO3

Figure 6.46

Heat

Carbonate
salt

Delivery
tube

Limewater

186

Interaction between MatterTHEME 3
Interpreting data:

1. What is the function of the limewater in the experiment?
 2. What gas is released when carbonate salts are decomposed by heat?
 3. Identify the carbonate salts that cannot be decomposed by heat.
Conclusion:

Is the hypothesis acceptable? What is the conclusion of the experiment?
Discussion:

1. Write an equation for the action of heat on carbonate salts that can be decomposed by heat.
 2. Generally, the decomposition of carbonate salts by heat can be represented by the word

equation below. Complete the word equation.

Heat   +

3. Name another carbonate salt that cannot be decomposed by heat.

Experiment 6.8

Prepare a complete report after carrying out this experiment.

Aim: To investigate the action of heat on nitrate salts.
Problem statement: Do nitrate salts decompose when heated to release nitrogen dioxide gas and

oxygen gas?
Hypothesis: Propose a suitable hypothesis for the experiment.
Variables: List all the variables involved in the experiment.
Materials: Solid sodium nitrate, NaNO3, solid magnesium nitrate, Mg(NO3)2, solid zinc

nitrate, Zn(NO3)2, solid lead(II) nitrate, Pb(NO3)2, solid copper(II) nitrate, Cu(NO3)2,
wooden splinter and blue litmus paper

Apparatus: Boiling tube, test tube holder, Bunsen burner and spatula
Procedure:

1. Discuss the experimental procedure with your group members.
Your discussion should include chemical tests for the

gases released.
 2. Identify the safety precautions when carrying out
  the experiment.
 3. Carry out the experiment with your teacher̕s permission.
 4. Record the salt colour before heating, the colour of the residue

when it is hot and cool, the colour of the gas released and its
effect on the moist blue litmus paper and the glowing wooden
splinter in a table.

Interpreting data:

1. Identify the nitrate salts that are not decomposed by heat.
 2. Name the brown coloured gas released in the experiment.
 3. What are the changes observed on the glowing wooden splinter? State the corresponding inference.

Figure 6.47 Apparatus set-up for
heating a nitrate salt

Glowing
wooden
splinter

Nitrate salt

Heat

Moist blue
litmus paper

195

Acid, Base and Salt CHAPTER 6
Prepare a complete report after carrying out this experiment.

When heated, most carbonate salts decompose to produce metal oxides and carbon dioxide
gas. For example, decomposition of zinc carbonate salt, ZnCO3 produces zinc oxide, ZnO and
carbon dioxide gas, CO2.

ZnCO3(s) → ZnO(s) + CO2(g)

When heated, nitrate salts decompose to produce metal oxides, nitrogen dioxide gas and oxygen
gas. The following equation shows the thermal decomposition of lead(II) nitrate salt, Pb(NO3)2.

2Pb(NO3)2(s) → 2PbO(s) + 4NO2(g) + O2(g)

Only several sulphate salts and chloride salts can be decomposed when heated.

Ammonium chloride : NH4Cl(s) → NH3(g) + HCl(g)
 Zinc sulphate : ZnSO4(s) → ZnO(s) + SO3(g)
 Iron(II) sulphate : 2FeSO4(s) → Fe2O3(s) + SO2(g) + SO3(g)

The cation or anion of a salt can be identified based on the gases released when the salt
undergoes thermal decomposition.

Carbon dioxide gas → Carbonate salt
 Nitrogen dioxide gas + Oxygen gas → Nitrate salt
 Ammonia gas → Ammonium salt

Conclusion:

Is the hypothesis acceptable? What is the conclusion of the experiment?
Discussion:

1. Write equations for the actions of heat on the nitrate salts that decompose other than
sodium nitrate.

2. Generally, the thermal decomposition of nitrate is represented by the word equation below.
Complete the equation.

Heat   +  +

ChemistryChemistry

The cation presents in some salts can be identified from the colour of the residue after heating.

Colour of residue
Metal oxide Cation present

in the saltHot Cold
Yellow White Zinc oxide, ZnO Zinc ion, Zn2+

Brown Yellow Lead(II) oxide, PbO Lead(II) ion, Pb2+

Black Black Copper(II) oxide, CuO Copper(II) ion, Cu2+

196

Interaction between MatterTHEME 3
Salt X decomposes when heated. A brown coloured gas is released and turns moist blue litmus
paper to red. The colour of the residue is brown when it is hot and yellow when it is cool.
Name salt X.

Solution:

The brown coloured gas is nitrogen dioxide. Salt X contains nitrate ion, NO3
–.

The residue is lead(II) oxide, PbO. Salt X contains lead(II) ion, Pb2+.
Salt  X is lead(II) nitrate, Pb(NO3)2.

Example 16

Yourself
TestTest

6.10

1. Identify the colourless gas that turns the colour of acidified potassium dichromate(VI)
solution, K2Cr2O7 from orange to green.

2. Copper(II) nitrate salt, Cu(NO3)2 is heated with high heat in a boiling tube. State the
observations on the colour of the residue and the gas released.

3. The following results are obtained in a laboratory activity to investigate the effect of heat
on a sample of salt Y.

•	 Colourless	gas	turns	limewater	cloudy.
•	The	colour	of	the	residue	is	yellow	when	it	is	hot	and	white	when	it	is	cooled.

Identify salt Y.

Qualitative Analysis6.11

Qualitative Analysis to Identify Cations and

Anions in Salts

Qualitative analysis of a salt is a technique used to identify the
cation and anion present in a salt by analysing its physical and
chemical properties. Figure 6.48 shows the steps that are involved
in the qualitative analysis of a salt.

Observation
on the physical

properties of
the salt

Effect of heat
on the salt

Test for anions
and cations

Confirmatory
tests for cations

and anions

Figure 6.48 Steps in the qualitative analysis of a salt

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
6.11.1 Identify the cation and

anion present in a salt
through experiment

6.11.2 Describe the
confirmatory tests to
identify cations and
anions

197

Acid, Base and Salt CHAPTER 6
Observations of the Physical Properties of Salts

Observing the physical properties of salts such as colour and solubility in water is the first step to
make inferences on the possibility of the presence of cations and anions in the salt. Even though
the solubility test of the salts does not confirm the identities of the ions present, it helps us narrow
down the possible identities of the ions present.

The colour of the salt is one of the physical properties that enables us to make inference on
the cation present in the salt. How is this possible? Carry out Activity 6.27 below.

Activity 6.27
Aim: To investigate the colour of the salts and their solubility in water.
Materials: Solid ammonium nitrate, NH4NO3, solid potassium nitrate, KNO3, solid sodium

chloride, NaCl, solid calcium carbonate, CaCO3, solid calcium nitrate, Ca(NO3)2,
solid magnesium sulphate, MgSO4, solid magnesium carbonate, MgCO3, solid zinc
sulphate, ZnSO4, solid zinc chloride, ZnCl2, solid iron(II) sulphate, FeSO4, solid iron(III)
chloride, FeCl3, solid lead(II) nitrate, Pb(NO3)2, solid lead(II) chloride, PbCl2, solid lead(II)
sulphate, PbSO4, solid copper(II) sulphate, CuSO4, solid copper(II) chloride, CuCl2,
solid copper(II) nitrate, Cu(NO3)2, solid copper(II) carbonate, CuCO3 and distilled water

Apparatus: Test tubes, test tube rack, glass rod, spatula and wash bottle
Procedure:

1. Observe and record the colour of each solid salt.
 2. Put a little amount of the salt into a test tube. Fill the test tube with distilled water and stir
  the mixture.
 3. Observe the solubility of the salt and the colour of the solution formed.
 4. Record all observations in Table 6.11.
Results:

Table 6.11

Type of salt Colour of
the salt

Solubility in water Colour of the
salt solutionYes No

Ammonium nitrate, NH4NO3

Potassium nitrate, KNO3

Interpreting data:

1. Name solid salts that are coloured:
(a) Green (b) Brown (c) Blue (d) White

2. Name green salts that are:
(a) Insoluble in water
(b) Soluble in water to form a blue solution
(c) Soluble in water to form a light green solution

For example, salt X is soluble in water. Hence, salt X might contain
NO ASaP ions, but definitely not HPA chloride or PBC sulphate and
most probably does not contain the carbonate ion, CO3

2–.

196

Interaction between MatterTHEME 3
Discussion:

1. Is the colour of the salt suitable to identify the cation presents in the salt? Explain.
 2. What is the colour of the solution formed when the white salt dissolves in water?
 3. Classify each salt as soluble salts or insoluble salts.
 4. What is the operational definition of insoluble salts?

Prepare a complete report after carrying out this activity.

All white soluble salts dissolve in water to form colourless salt solutions. Salts form coloured
solutions due to the presence of ions in transition elements.
For example,

Blue solution : possibly contains copper(II) ion, Cu2+

Brown solution : possibly contains iron(III) ion, Fe3+

Green solution : possibly contains iron(II) ion, Fe2+

Table 6.12 shows the colour of some salts in the solid state
 and in aqueous solution.

Table 6.12 Colour of salts in solid state and in aqueous solution

Salt
Colour

Solid state Aqueous solution
Salts containing iron(II) ion, Fe2+ Green Green/light green

Salts containing iron(III), Fe3+ Brown Brown/yellowish brown

Copper(II) sulphate, CuSO4
Copper(II) nitrate, Cu(NO3)2

Blue Blue

Copper(II) chloride salt, CuCl2 Green Blue

Copper(II) carbonate salt, CuCO3 Green Insoluble in water

Figure 6.49 shows the example on the qualitative analysis of a solid X which is green in
colour and three possible results.

Add distilled water

Solid X might be CuCO3
salt or iron(II) salt which
is insoluble in water.

Solid X might be
iron(II) salt which
is soluble in water.

Solid X might be
CuCl2 salt which
is soluble in water.

Glass rod

Green
precipitate

Glass rod

Green colour
solution

Glass rod

Blue colour
solution

Solid X in green colour

Figure 6.49 Qualitative analysis based on the solubility of the salt and its colour

ChemistryChemistry

Other than iron(II) ion, Fe2+,
nickel(II) ion, Ni2+ and
chromium(III) ion, Cr3+

also give green colour in
aqueous solutions.

197

Acid, Base and Salt CHAPTER 6
Effect of Heat on Salts and Gas Tests

The gas released when a salt is heated can be identified through its colour, smell, action on moist
litmus paper or best, by conducting a gas test. After heating the salt, we can make an inference on
the ions that might be present based on the colour of the residue and the gas identified, as shown
in Table 6.13 and Table 6.14.
 Table 6.13 Table 6.14

Colour of residue Inference
Black Salt contains Cu2+ ion

Brown Salt contains Fe3+ ion

Yellow when hot,
white when cool Salt contains Zn2+ ion

Brown when hot,
yellow when cool Salt contains Pb2+ ion

Gas produced Inference

Gas turns limewater cloudy Carbonate salt

Gas is brown and acidic Nitrate salt

Gas is pungent and alkaline Ammonium salt

Gas ignites the glowing
wooden splinter

Might be nitrate
salt or Ag2CO3

Figure 6.50 and 6.51 show the examples of qualitative analysis based on the effect of heat on
salts X and Y and the corresponding gas tests. However, the qualitative analysis carried out could
not identify the presence of cation in the salts.

Salt X is a carbonate salt that possibly contains Ca2+ ion, Mg2+ ion
or Al3+ ion and not K+ ion or Na+ ion because potassium carbonate
and sodium carbonate are not decomposed by heat.

Figure 6.50 Qualitative analysis based on the effects of heat on salt X and gas test

Salt X is white
in colour

The colour of the residue is
white when it is hot and cool Colourless gas

Limewater turns
cloudy

White solid
insoluble in water

Heated with
high heat

Pass through
limewater

Add water

Carbon dioxide gas
released. Salt X contains
carbonate ion, CO3

2-

Salt X is definitely an
insoluble salt

Salt X is definitely not
Zn2+, Fe2+, Fe3+, Pb2+ or Cu2+

Salt X is not Fe2+,
Fe3+ or Cu2+

+

196

Interaction between MatterTHEME 3
Anion Tests

Only four anions are needed to be identified at this level, which are:

Carbonate ion, CO3
2–   Chloride ion, Cl–

Sulphate ion, SO4
2–   Nitrate ion, NO3

–

Certain anions can be identified from testing the gases released when the salt undergoes
decomposition by heat. However, the identity of the anion in a salt still needs to be confirmed
through anion tests. Figure 6.52 shows the flow chart of the anion tests.

Figure 6.52  Summary of the anion tests

Nitric acid, HNO3 and barium
nitrate solution, Ba(NO3)2  can
replace hydrochloric acid, HCl and
barium chloride solution, BaCl2 to
test for the presence of sulphate
ion, SO4

2–.
CO3

2– Cl– SO4
2– NO3

–

Anion tests

Gas turns
limewater

cloudy

White
precipitate

White
precipitate

Brown
ring

+ Dilute H2SO4
+ FeSO4(aq)
+ Concentrated H2SO4

+ Dilute HCl
+ BaCl2(aq)

+ Dilute HNO3
+ AgNO3(aq)+ Dilute acid

Figure 6.51 Qualitative analysis based on the effects of heat on salt Y and gas tests

Salt Y is white in
colour

The colour of the residue is
white when it is hot and cool

Colourless
gas

Brown
gas

The glowing wooden
splinter rekindles

Colourless
solution

Heated with
high heat

Test with glowing
wooden splinterAdd water

Brown nitrogen dioxide gas
and oxygen gas present. Salt Y
contains nitrate ion, NO3

–

Salt Y is a
soluble salt

Salt Y is definitely not
Zn2+, Fe2+, Fe3+, Pb2+ or Cu2+

Salt Y is not Fe2+,
Fe3+ or Cu2+

+ +

Salt Y is a nitrate salt that possibly contains Ca2+ ion, Mg2+ ion
or Al3+ ion and not K+ ion and Na+ ion because potassium nitrate
and sodium nitrate do not produce a brown gas.

197

Acid, Base and Salt CHAPTER 6
The test for anions in an aqueous solution of the salt can be performed as in Experiment 6.9.

Experiment 6.9

Aim:  To identify the anions present in aqueous salt solutions.
Problem statement: How to identify the anions that are present in aqueous solutions?
Hypothesis: The anions present can be identified through observations from the chemical tests

on anions.
Variables:

(a) Manipulated : Types of anions present in the solution
(b) Responding : Observations made
(c) Fixed : Volume of aqueous salt solution
Materials: 2.0 mol dm–3 nitric acid, HNO3, 0.1 mol dm–3 silver nitrate solution, AgNO3,

2.0 mol dm–3 hydrochloric acid, HCl, 1.0 mol dm–3 barium chloride solution, BaCl2,
1.0 mol dm–3 sulphuric acid, H2SO4, 1.0 mol dm–3 iron(II) sulphate solution, FeSO4,
concentrated sulphuric acid, H2SO4, sample of salt A (solid sodium carbonate, Na2CO3),
sample of salt B (solid sodium chloride, NaCl), sample of salt C (solid sodium
sulphate, Na2SO4), sample of salt D (solid sodium nitrate, NaNO3), distilled water
and limewater

Apparatus: Test tubes, test tube holder, test tube rack, glass rod, dropper, rubber stopper with
delivery tube, spatula, 100 cm3 beaker, 10 cm3 measuring cylinder

Procedure:

Preparing aqueous solutions of the salts

1. Put salt sample A provided by the teacher into a beaker.
 2. Dissolve salt sample A with distilled water to produce 20 cm3 of salt A solution.

3. Pour 2 cm3 of salt A solution into 4 test tubes. Label the test tubes as A1, A2, A3 and A4.
 4. Repeat steps 1 until 3 using salt samples B, C and D.

(I)  Test for carbonate ion, CO
3

2–

1. Add 2 cm3 of 2.0 mol dm-3 hydrochloric acid, HCl into
the test tube labelled A1. If effervescence occurs, flow
the gas into limewater as shown in Figure 6.53.

2. Record the observation.
 3. Repeat steps 1 and 2 using solutions B1, C1 and D1.

(II)  Test for chloride ion, Cl
–

1. Add excess of 2.0 mol dm–3 nitric acid, HNO3
 into the test

tube labelled A2, followed by 2 cm3 of 0.1 mol dm–3 silver
nitrate solution, AgNO3.

2. Record the observation.
 3. Repeat steps 1 and 2 using solutions B2, C2 and D2.

Figure 6.53

Limewater
A1 solution

Be careful when using silver
nitrate solution, AgNO3. Skin
that comes into contact with
silver nitrate solution, AgNO3
would turn brown. The brown
spots would disappear only
after a few days.

202

Interaction between MatterTHEME 3
(III)  Test for sulphate ion, SO
4

2–

1. Add 2.0 mol dm–3 hydrochloric acid, HCl into the test tube labelled A3, followed by
2.0 mol dm-3 barium chloride solution, BaCl2.

2. Record the observation.
 3. Repeat steps 1 and 2 with solutions B3, C3 and D3.

(IV)  Test for nitrate ion, NO
3

–

1. Add 2 cm3 of 1.0 mol dm–3 sulphuric acid, H2SO4 into the test tube labelled A4, followed by
2 cm3 of 1.0 mol dm–3 iron(II) sulphate solution, FeSO4.

2. Shake the mixture.

3. Carefully, drip a few drops of concentrated sulphuric acid, H2SO4 slowly
down the wall of the tilted test tube as shown in Figure 6.54.

4. Slowly set the test tube upright.
 5. Record the observation.
 6. Repeat steps 1 to 5 using solutions B4, C4 and D4.
Results:

Table 6.15

Test
Observation

Salt A solution Salt B solution Salt C solution Salt D solution
Carbonate ion, CO3

2–

Chloride ion, Cl–

Sulphate ion, SO4
2–

Nitrate ion, NO3
–

Interpreting data:

1. What was the gas released that causes the effervescence?
 2. (a) Name the white precipitate formed in the test for chloride ion, Cl–.

(b) Write the ionic equation for the formation of the precipitate in 2(a).
 3. (a) What is the name of the white precipitate formed in the test for sulphate ion, SO4

2–.
(b) Write the ionic equation for the formation of the white precipitate in 3(a).

4. Identify the anion in the following samples:
(a) Salt A (b) Salt B (c) Salt C (d) Salt D

Conclusion:

Is the hypothesis accepted? What is the conclusion of the experiment?
Discussion:

1. What is the purpose of adding excess acid in the test for chloride ion, Cl– and sulphate ion, SO4
2–

before adding the other reagents?
 2. A student performs a test for the chloride ion, Cl– in a sample of  salt solution. He added the

silver nitrate solution, AgNO3 without first adding an excess of nitric acid, HNO3. He then
made the inference of the presence of chloride ions, Cl– in the sample when he observed a
white precipitate being formed. Was the inference correct? Why?

Figure 6.54

A4 solution

Concentrated
sulphuric acid,
H2SO4

Prepare a complete report after carrying out this experiment.

203

Acid, Base and Salt CHAPTER 6
Based on the test for the carbonate ion, CO3
2– the reaction between acid and carbonate

ions, CO3
2– produces carbon dioxide gas that turns limewater cloudy.

2H+(aq) + CO3
2–(aq) → CO2(g) + H2O(l)

In the test for chloride ion, Cl–, silver ion, Ag+ is used to detect
the presence of chloride ions, Cl–. If chloride ions, Cl– is present,
hence the white precipitate of silver chloride, AgCl is produced.
However, the carbonate ion, CO3

2– also gives the same observation
when reacting with silver ion, Ag+ due to the formation of a white
precipitate of silver carbonate, Ag2CO3. Therefore, an excess of
nitric acid, HNO3 has to be added before adding silver nitrate
solution, AgNO3. If effervescence occurs when nitric acid, HNO3
was added, then, the presence of carbonate ion, CO3

2– is
confirmed. However, if no effervescence occurs, the formation of
white precipitate confirms the presence of the chloride ion, Cl–.

For the test of sulphate ion, SO4
2–, barium ion, Ba2+  used to detect the presence of sulphate

ion, SO4
2– because the reaction between the barium ion, Ba2+  and sulphate ion, SO4

2– produces a
white precipitate of barium sulphate, BaSO4. Hydrochloric acid, HCl was added in excess before
adding barium chloride solution, BaCl2 for the same reason as in the test for chloride ion, Cl-, that
is to detect and eliminate the carbonate ion, CO3

2– that might be present.
Table 6.16  Qualitative analysis based on anion tests

Anion test Observation Inference

Test for carbonate ion, CO3
2– Effervescence

occurs. The gas
released turns
limewater cloudy.

Carbonate ion, CO3
2–

is present.
Ionic equation:
2H+(aq) + CO3

2–(aq)
→ CO2(g) + H2O(l)

Test for chloride ion, Cl– White precipitate
is formed.

Chloride ion, Cl –

is present.
Ionic equation:
Ag+(aq) + Cl–(aq)
→ AgCl(s)

Test for sulphate ion, SO4
2– White precipitate

is formed.
Sulphate ion, SO4

2–

is present.
Ionic equation:
Ba2+(aq) + SO4

2–(aq)
→ BaSO4(s)

Test for nitrate ion, NO3
– Brown ring

is formed.
Nitrate ion, NO3

–

is present.

Reaction between
concentrated sulphuric
acid, H2SO4 and nitrate ion,
NO3

– produces nitrogen
monoxide, NO. When
nitrogen monoxide, NO
combines with iron(II)
sulphate, FeSO4, a complex
compound of nitrosyliron(II)
sulphate, FeSO4.NO, which
is a brown ring, is observed.

Salt
solution

Dilute acid

Salt
solution

AgNO3
(aq)

HNO3
(aq)

Salt
solution

HCl
(aq)

BaCl2
(aq)

Salt
solution

Dilute
H2SO4

FeSO4
(aq)

Concentrated
H2SO4

ChemistryChemistry

202

Interaction between MatterTHEME 3
Aim: To identify the cations present in aqueous solutions.
Problem statement:  How to identify the cations present in aqueous solutions?
Hypothesis: Types of cations present in a solution can be identified through observations of the

cation tests.
Variables:

(a) Manipulated : Types of cations present in aqueous solutions
(b) Responding : Observations made
(c) Fixed : Volume of aqueous salt solution
Materials: 2.0 mol dm–3 sodium hydroxide solution, NaOH, 2.0 mol dm–3 ammonia solution, NH3,

1.0 mol dm–3 calcium nitrate solution, Ca(NO3)2, 1.0 mol dm–3 magnesium nitrate
solution, Mg(NO3)2, 1.0 mol dm–3 aluminium nitrate solution, Al(NO3)3, 1.0 mol dm–3
zinc nitrate solution, Zn(NO3)2, 1.0 mol dm–3 iron(II) sulphate solution, FeSO4,
1.0 mol dm–3 iron(III) chloride solution, FeCl3, 1.0 mol dm–3 lead(II) nitrate
solution, Pb(NO3)2, 1.0 mol dm-3 copper(II) sulphate solution, CuSO4 and 1.0 mol dm–3
ammonium nitrate solution, NH4NO3

Apparatus: Test tubes, test tube holder, test tube rack, dropper, 100 cm3 beaker, red litmus paper,
Bunsen burner and 10 cm3 measuring cylinder

Procedure:

2 cm3 of
salt solution

Heat

Moist red
litmus paper

No precipitate

Precipitate dissolves
in excess aqueous
alkali

White/coloured
precipitate

Add a few
drops of
aqueous alkali

Add aqueous
alkali until
excess

Shake the mixture

Shake it
evenly Precipitate does not

dissolve in excess
 aqueous alkali

Figure 6.55 Steps in identifying the cations in aqueous solutions

Cation Tests

Alkalis such as sodium hydroxide solution, NaOH, and ammonia solution, NH3 are two main
reagents used to test the presence of cations. The hydroxide ion, OH– from both solutions combine
with most metal ions to form a precipitate of metal hydroxide. For example,

Zn2+(aq)  +  2OH–(aq)  →  Zn(OH)2(s)
 Metal ion Hydroxide ion  Metal hydroxide precipitate

Inference about the cations present can be made based on the observation on the colour of the
precipitate and its solubility in an excess of alkali solution.

Experiment 6.10

205

Acid, Base and Salt CHAPTER 6
Using sodium hydroxide solution, NaOH

1. Based on Figure 6.55, discuss the experimental procedures with your group members.
 2. Determine the safety precautions needed in carrying out the experiment.
 3. Carry out the experiment with your teacher̕s permission.
 4. Record all the observations in Table 6.17.

Using ammonia solution, NH
3

1. Repeat the procedure in A by using ammonia solution, NH3 to replace sodium hydroxide
solution, NaOH.

2. Record all the observations in Table 6.17.
Results:

Table 6.17

Salt solution Cation

Observation

Small amount of
sodium hydroxide

solution, NaOH

Excess amount
of sodium
hydroxide

solution, NaOH

Small amount
of ammonia

solution, NH3

Excess amount
of ammonia

solution, NH3

Calcium nitrate,
Ca(NO3)2
Magnesium nitrate,
Mg(NO3)2

Aluminium nitrate,
Al(NO3)3
Zinc nitrate,
Zn(NO3)2
Iron(II) sulphate,
FeSO4
Iron(III) chloride,
FeCl3
Lead(II) nitrate,
Pb(NO3)2
Copper(II)
sulphate, CuSO4
Ammonium
nitrate, NH4NO3

Interpreting data:

Based on the experiment in part A:
 1. List the cations that produce precipitates which are:

(a) Green (b) Brown (c) Blue (d) White
 2. Which salt solution does not show any changes on the addition of sodium hydroxide

solution, NaOH. What is the gas released upon heating?
 3. Name the cations that produce white precipitates which are:

(a) Soluble in an excess amount of sodium hydroxide solution, NaOH
(b) Insoluble in an excess amount of sodium hydroxide solution, NaOH

202

Interaction between MatterTHEME 3
Based on the experiment in part B:
 1. List the cations that produce precipitates which are:

(a) Green (c) Blue
(b) Brown (d) White

2. Which salt solution does not show any changes on the addition of ammonia solution, NH3?
 3. Name the cations that produce white precipitates which are:

(a) Soluble in excess amount of ammonia solution, NH3
(b) Insoluble in excess amount of ammonia solution, NH3

4. Which cations form a precipitate that is soluble in excess amount of ammonia, NH3 to produce
a dark blue solution?

Conclusion:

Is the hypothesis accepted? What is the conclusion of this experiment?

Discussion:

1. Identify the cations that react with both alkalis to produce white precipitates that are soluble in
an excess amount of the alkali.

2. Based on the cations identified in question 1, write ionic equations for the formation of
  the precipitates.

Figure 6.56 shows the flow chart that summarises the reactions between cations and sodium
hydroxide solution, NaOH.

Figure 6.56 Reactions between cations and sodium hydroxide solution, NaOH

Soluble in excess amount of
NaOH solution to produce
colourless solution

Dissolve in
excess of NaOH

solution

Insoluble in
excess amount of
NaOH solution

No

No

NoYes

Yes

Yes

Insoluble in excess amount
of NaOH solution

Heat

Moist red litmus
paper turns blue

Salt
solution

Add a few drops
 of NaOH

Does precipitate
form?

Does
coloured precipitate

form?
Presence of

NH4
+ ion

Zn2+ Al3+ Mg2+ Ca2+Pb2+ Fe2+ Fe3+ Cu2+

NH3 gas

Prepare a complete report after carrying out this experiment.

207

Acid, Base and Salt CHAPTER 6
Figure 6.57 shows the flow chart that summarises the reaction between cations and ammonia
solution, NH3.

Figure 6.57 Reaction between cations and ammonia solution, NH3

Salt solution X is blue.
Test for cations with sodium hydroxide solution, NaOH:

Salt
solution X

Blue
precipitate
forms

Blue precipitate does
not dissolve in excess
amount of NaOH
solution

A few
drops of
NaOH

Add NaOH solution
until excess

Test for cations with ammonia solution, NH3:

Salt
solution X

Blue
precipitate
forms

Blue precipitate
dissolves to form
dark blue solution

A few
drops
of NH3

Add NH3 solution
until excess

Example 17

No

No

NoYes

Yes

Yes

Ca2+ ion or
NH4

+ ion might
be present

Zn2+ Mg2+ Al3+Pb2+
Fe2+ Fe3+ Cu2+

Salt
solution

Add a few drops
 of NH3 solution

Does precipitate
form?

Does
coloured precipitate

form?

Soluble in
excess amount of

NH3 solution

Soluble in excess amount
of NH3 solution to form
colourless solution

Soluble in excess amount
of NH3 solution to produce
dark blue solution

Insoluble in excess
amount of NH3 solution

Insoluble in
excess amount
of NH3 solution

Cu2+ ion is present.

202

Interaction between MatterTHEME 3
Salt solution X is colourless.
Test for cations with sodium hydroxide solution, NaOH:

White
precipitate
forms

Zn2+, Al3+, Pb2+, Mg2+, Ca2+

might be present
Mg2+, Ca2+

might be present

White precipitate
does not dissolve in
excess amount of
NaOH solution

A few
drops of
NaOH

Add NaOH solution
until excess

Salt
solution X

Test for cations with ammonia solution, NH3:

Salt
solution X

No change

Ca2+, NH4
+

might be present

A few
drops
of NH3

Salt solution X is colourless.
Test for cations with sodium hydroxide solution, NaOH:

Salt
solution X

White
precipitate
forms

Zn2+, Al3+, Pb2+, Mg2+, Ca2+

might be present
Zn2+, Al3+, Pb2+

might be present

White precipitate
dissolves in excess
amount of NaOH solution

A few
drops of
NaOH

Add NaOH solution
until excess

Test for cations with ammonia solution, NH3:

Salt
solution X

White
precipitate
forms

Zn2+, Al3+, Pb2+, Mg2+

might be present
Al3+, Pb2+,Mg2+

might be present

White precipitate does
not dissolve in excess
amount of NH3 solution

A few
drops
of NH3

Add NH3 solution
until excess

Example 18

Example 19

Ca2+ ion is present.

Al3+ or Pb2+ ions
might be present.

209

Acid, Base and Salt CHAPTER 6
Confirmatory Tests for Cations

Both Al3+ ion and Pb2+ ion give the same observations when tested with sodium hydroxide
solution, NaOH and ammonia solution, NH3. Thus, a confirmatory test is required to differentiate
between Pb2+ ion and Al3+ ion. Other than that, ions such as Fe2+, Fe3+ and NH4

+ too can be
confirmed using specific reagents.

Experiment 6.11

Aim: To confirm the presence of cations (NH4
+, Fe2+, Fe3+, Pb2+) in aqueous solutions.

Problem statement: How to confirm the presence of cations (NH4
+, Fe2+, Fe3+, Pb2+) in

aqueous solutions?
Hypothesis: Construct a hypothesis which is suitable for this experiment.
Variables: Name all variables involved in this experiment.
Procedure:

Method I: Confirmation of
ammonium ion, NH4

+

Method II: Confirmation of
iron(II) ion, Fe2+

Method III: Confirmation of
iron(III) ion, Fe3+

2 cm3 of ammonium
chloride solution, NH4Cl

Add a few
drops of
Nessler reagent

2 cm3 of iron(II)
sulphate solution, FeSO4

Add a few drops
of potassium
hexacyanoferrate(III)
solution, K3Fe(CN)6

2 cm3 of iron(III)
chloride solution, FeCl3

Add a few drops
of potassium
hexacyanoferrate(III)
solution, K4Fe(CN)6

Method IV: Confirmation of lead(II) ion, Pb2+

2 cm3 of lead(II) nitrate
 solution, Pb(NO3)2

1 cm3 of potassium
iodide solution, KI

3 cm3
of distilled
water

Heat Cooled

Figure 6.58 Confirmatory tests for ammonium ion, iron(II) ion, iron(III) ion and lead(II) ion

1. Based on Figure 6.58, list the apparatus and reagents that are needed for this experiment.
 2. Discuss the experimental procedure for the experiment with your group members. Make sure

you repeat Method III by using potassium thiocyanate solution, KSCN instead of potassium
hexacyanoferate(II), K4Fe(CN)6.

3. Carry out the experiment with your teacher̕s permission.
 4. Record your observations in Table 6.18.

210

Interaction between MatterTHEME 3
Results:

Table 6.18

Confirmatory test Observation
Method I:
Confirmatory test for ammonium ion, NH4

+

Method II:
Confirmatory test for iron(II) ion, Fe2+

Method III:
Confirmatory test for iron(III) ion, Fe3+

(a) Using potassium hexacyanoferate(II) solution, K4Fe(CN)6
(b) Using potassium thiocyanate solution, KSCN

Method IV:
Confirmatory test for lead(II) ion, Pb2+

Conclusion:

Is the hypothesis accepted? What is the conclusion of this experiment?
Discussion:

1. Write an ionic equation for the reaction between potassium iodide solution, KI and lead(II)
nitrate solution, Pb(NO3)2.

2. Other than Nessler reagent, what are other reagents that can be used to confirm the presence
of ammonium ion, NH4

+? Briefly explain how the chemical test is carried out.
 3. Predict the observation obtained if potassium chloride solution, KCl is used instead of

potassium iodide solution, KI in Method IV.

Ammonium ion, NH4
+ Iron(II) ion, Fe2+ Iron(III) ion, Fe3+

Brown precipitate Dark blue precipitate  Blood red
solution

Dark blue
precipitate

ChemistryChemistry

•	 Potassium	hexacyanoferate(II)	solution,	K4Fe(CN)6	is	used	to	confirm	the	presence	of	iron(III)	ion,	Fe3+.
	 If	this	solution	is	added	to	an	aqueous	solution	that	contains	iron(II)	ion,	Fe2+,	a	light blue precipitate
 is	formed.
•	 Potassium	hexacyanoferate(III)	solution,	K3Fe(CN)6	is	used	to	confirm	the	presence	of	iron(II)	ion,	Fe2+.
	 If	this	solution	is	added	to	an	aqueous	solution	containing	iron(III),	Fe3+,	a	greenish brown colour
	 is	obtained.

+ Nessler
   reagent

+ K3Fe(CN)6
+ K4Fe(CN)6 + KSCN

Confirmatory tests for NH4
+, Fe2+ and Fe3+

Prepare a complete report after carrying out this experiment.

Figure 6.59 Confirmatory tests for NH4
+ ion, Fe2+ ion and Fe3+ ion

211

Acid, Base and Salt CHAPTER 6
Al3+ ion and Pb2+ ion form white precipitates that are insoluble in an excess of alkali solution.
Thus, potassium iodide solution, KI is used to differentiate between these two ions.

Figure 6.61 Qualitative analysis of salts

Figure 6.60 Confirmatory tests for Al3+ ion and Pb2+ ion

Qualitative Analysis on Unknown Salts

In order to identify the cations and anions in an unknown salt, you need to perform a systematic
analysis according to the order of the test.
 Figure 6.61 shows the steps that are involved in the qualitative analysis of salts. Carry out
Activity 6.28 to identify the anions and cations in the given salt.

Tests for anions

Test for gasSalt

Test for cations

Add distilled water

Observe the colour Heating

Ions in
aqueous solution

Add dilute
nitric acid, HNO3

Yes

No
Soluble?

Salt solution
which may
contain Al3+

or Pb2+ ion

A few drops
of potassium
iodide
solution, KI

Possibility I

Possibility  II

Heat
The yellow
precipitate forms
again after cooling

Yellow
precipitate

forms

No precipitate forms

The yellow precipitate
dissolved in water
to form colourless
solution

The presence
of Pb2+ is
confirmed.

The presence of Al3+

is confirmed.

212

Interaction between MatterTHEME 3
Activity 6.28
Aims: To identify the cation and anion in L2 solid.
Materials:  L2 solid, 2.0 mol dm–3 sodium hydroxide solution, NaOH, 2.0 mol dm–3 ammonia

solution, NH3, 2.0 mol dm–3 nitric acid, HNO3, 0.1 mol dm–3 silver nitrate solution, AgNO3,
2.0 mol dm–3 hydrochloric acid, HCl, 1.0 mol dm–3  barium chloride solution, BaCl2,
distilled water, blue litmus paper and wooden splinter

Apparatus: Test tubes, dropper, test tube rack, test tube holder, Bunsen burner, 10 cm3 measuring
cylinder, 100 cm3 beaker, spatula and glass rod

Procedure:

1. Carry out qualitative analysis to identify the cation and anion in L2 solid.
 2. Put half a spatula of L2 solid into a test tube. Add the remaining L2 solid into a beaker.

Add 25 cm3 of distilled water into the beaker to dissolve the L2 solid.
 3. Divide the L2 solution into four portions to be used for the chemical tests below:

• Tests to identify the cation

Table 6.19

Chemical test Observation Inference
(a) Pour 2 cm3 of L2 solution into a test tube.

Add 2.0 mol dm–3 sodium hydroxide solution, NaOH
until excess.

(b) Add 2 cm3 of L2 solution into a test tube.
Add 2.0 mol dm–3 ammonia solution, NH3 until excess.

• Tests to identify the anion

Table 6.20

Chemical test Observation Inference
(a) Heat L2 solid with high heat in a test tube. Test the gas

released with a glowing wooden splinter and moist blue
litmus paper.

(b) Pour 2 cm3 of L2 solution into a test tube.
Add 2.0 mol dm–3 hydrochloric acid, HCl followed by
1.0 mol dm–3 barium chloride solution, BaCl2.

(c) Pour 2 cm3 of L2 solution into a test tube.
Add 2.0 mol dm–3 nitric acid, HNO3 followed by
0.1 mol dm–3 silver nitrate solution, AgNO3.

4. Record the observations for the activity.
Interpreting data:

1. State the inference that corresponds to each observation.
 2. Based on the chemical tests, name L2.

Teacher's note

http://bit.ly/
2P6Cu5G

CT

Prepare a complete report after carrying out the activity.

213

Acid, Base and Salt CHAPTER 6
To identify the cations and anions in an unknown salt

You are provided with salt Q1 that contains one cation and anion. Plan a series of chemical tests to
identify the cation and anion in salt Q1.
 1. Build a flow chart to help you plan your qualitative technique of salt analysis.
 2. Identify and list the reagents and apparatus needed.
 3. Discuss with your teacher before carrying out the experiment.
 4. Carry out the qualitative analysis of salts in the correct order.
 5. Write a report on the qualitative analysis of the salt as described

in Activity 6.28. Identify salt Q1 in your report.

Yourself
TestTest

6.11

1. The aqueous solution of a salt is pale green. What cation might be present in the salt?

2. When a sulphate salt is decomposed by heat, the gas released decolourises the purple
colour of potassium manganate(VII) solution, KMnO4. What inference can be made on the
gas released?

3. When an aqueous solution of a salt Q was tested with alkali solutions, the following
observations was obtained.

•	 A	white	precipitate	that	is	insoluble	in	an	excess	of	sodium	hydroxide	solution,	NaOH
•	No	change	on	the	addition	of	ammonia	solution,	NH3 to the salt solution.

What cation may be present in the salt?

4. Three salt samples S1, S2 and S3 contain the zinc ion, Zn2+, aluminium ion, Al3+ and
lead(II) ion, Pb2+ respectively. Describe the qualitative analysis carried out to confirm the
presence of the ions in each solution.

Activity 6.29
CT

While conducting qualitative analysis of salts,
systematic and conscientious attitudes are very
important in order to identify the cation and
anion in a salt correctly.

Century
Skills21st

Teacher's note

http://bit.ly/
2J6jrVl

214

Interaction between MatterTHEME 3
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215

Acid, Base and Salt CHAPTER 6
Self Reflection

1. What new knowledge have you learned in Acid, Base and Salt?
 2. Which is the most interesting subtopic in Acid, Base and Salt? Why?
 3. Give a few examples on the application of Acid, Base and Salt in daily life.
 4. Rate your performance in Acid, Base and Salt on a scale of 1

to 10; 1 being the lowest and 10 the highest. Why would you
rate yourself at that level?

5. What can you do to improve your mastery in Acid, Base
and Salt?

http://bit.ly/
2OSLFXq

Achievement 6

1. Table 1 shows the properties of two acids, P and Q.
Table 1

Type of acid P Q

Formula of the acid H2SO4 CH3COOH

pH value of 0.1 mol dm–3 solution 0.7 2.9

Based on the information above, answer the following questions:
(a) What is the basicity of the acid:

(i) P? (ii) Q?
(b) Explain your answer in (a).
(c) Explain why acid P and acid Q have different pH values.

(d) When 10 cm3 of acid P is added into a test tube containing zinc, effervescence occurs.
(i) Write a chemical equation for the reaction that occurs.

(ii) Calculate the volume of gas released at room conditions.

[Molar volume: 24 dm3 mol–1 at room conditions]
(e) You are required to prepare 100 cm3 of 0.05 mol dm–3 acid P. Explain briefly how you

would prepare dilute acid P.

2. An experiment was carried out to determine the concentration of sodium hydroxide solution,
NaOH by titrating 0.5 mol dm–3 sulphuric acid, H2SO4 with 25 cm3 of sodium hydroxide
solution, NaOH.

Table 2
Titration I II III

Final burette reading (cm3) 25.55 48.20 28.50

Initial burette reading (cm3) 0.45 23.00 3.20
Volume of sulphuric acid, H2SO4 used (cm3)

216

Interaction between MatterTHEME 3
(a) Complete Table 2. Determine the average volume of sulphuric acid, H2SO4 used.

(b) Write a chemical equation for the neutralisation reaction between sulphuric acid, H2SO4
and sodium hydroxide solution, NaOH.

(c) Determine the concentration of the sodium hydroxide solution, NaOH used in
 this experiment.

3. Figure 1 shows the flow chart for a series of reactions that occurs on solid X salt.
Reaction W

Salt X Black solid P

Blue
solution Y

Brown gas Q
Heat

+ a little amount
sodium hydroxide

solution

+ a little amount
aqueous ammonia

solution

Dissolves
in water

Blue precipitate dissolves in
excess amount of aqueous

ammonia solution turns into
dark blue solution

Blue precipitate insoluble
in excess amount of sodium

hydroxide solution

Blue
precipitate

Blue
precipitate + excess amount of

aqueous ammonia
solution

+ excess amount of
sodium hydroxide

solution

Colourless gas R+ +

Figure 1

(a) Based on the flow chart above, identify:
(i) Black solid P (iii) Colourless gas R
(ii) Brown gas Q (iv) Blue solution Y

(b) Write a chemical equation to represent the decomposition of salt X by heat.
(c) Explain briefly how you would confirm the anion presence in salt X?
(d) The black solid P can be changed into salt X through reaction W. Suggest a chemical that

is suitable for changing the black solid P to salt X. Then, explain briefly how the black
solid P can be changed to salt X through reaction W.

CornerEnrichmen
 1. Hooi See’s mother is very fond of capstone because she loves

blue crystals. However, the price of the capstone is very
expensive. As a student studying chemistry, how can you
help Hooi See to prepare a large and beautiful blue crystal in
the laboratory as a present to Hooi See’s mother? Prepare the
crystal by including the labelled diagram.

Check   AnswersAnswers

http://bit.ly/
2pHAdTW

217

Acid, Base and Salt CHAPTER 6
What will you learn?

7.1	 Determining	Rate	of	Reaction
7.2	 Factors	Affecting	Rate	of	Reactions
7.3	 Application	of	Factors	that	Affect	the	Rate	of

Reaction	in	Daily	Life
7.4	 Collision	Theory

Rate of
Reaction7

CHAPTER

Reactant
 Product
 Rate of reaction
 Catalyst
 Collision theory
 Activation energy
 Effective collision
 Energy profile
diagram

KeywordsKeywords

218
What	is	the	difference	between	average
rate	of	reaction	and	instantaneous	rate
of	reaction?

How	does	temperature	affect	the	rate
of	reaction?

Why	does	food	cook	faster	when	they	are
in	smaller	pieces?

Nowadays, the use of blow torch in food preparation
is gaining popularity. The flame from the blow
torch is produced from the burning of butane gas
at high concentration, and the reaction is fast. The
high temperature of the flame increases the rate of
reaction in the food. As a result, food such as meat
can be cooked in a short time.  If the meat is grilled as
normal, the rate of reaction would be slower. Other
than temperature and concentration, what other
factors would affect the rate of reaction?

Bulletin

219
Determining Rate of Reaction7.1

Classification of Rate of Reactions

There are a variety of chemical reactions that occur in our
surroundings. Did you realise that chemical reactions also occur
in our bodies? Do such reactions occur at a fast or slow rate?
Figure 7.1 shows several chemical reactions taking place.

Figure 7.1 Examples of fast and slow reactions

Electric cells
reaction

Ignition of matches

Rock erosion

Combustion of gases

Fermentation

Fireworks

Food decay Corrosion of metals

Photosynthesis

Fast
reactions

Slow
reactions

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
7.1.1 Classify fast and slow

reactions that occur in
daily life

7.1.2 Explain the meaning of
the rate of reaction

7.1.3 Identify changes
which can be observed
and measured during
chemical reactions
through activity

7.1.4 Determine the
	 •	 average	rate	of	reaction
	 •	 instantaneous	rate

of reaction
7.1.5 Solve numerical

problems based on
the average and
instantaneous rate
of reaction

220

Interaction between MattertheMe 3
Meaning of the Rate of Reaction

What do you understand by the rate of a reaction? The rate of
reaction is the changes in the quantity of the reactant per unit
time or the changes in the quantity of product per unit time.

Rate of reaction =

Change in the quantity of
reactant or product
Time taken for the

change to occur

During the reaction, the quantity of reactant used decreases,
while the quantity of product formed increases.

The unit for mass of solids is measured in g, while the volume of gases in cm3 or dm3. For the
quantity of soluble substances, the concentration is measured in mol dm–3. The choice in unit of
time depends on the rate of reaction. For fast reactions, the time is measured in seconds, while for
slow reactions, minutes is used. Therefore, the units for rate of reaction that are commonly used are:

Unit for rate of reaction:
•	 g	s–1 or g  minute–1

•	 cm3 s–1 or cm3  minute–1

•	mol	dm–3 s–1 or mol dm–3  minute–1

Changes that Occur during Reactions

Determining rate of reaction must be made based on the changes that are observable and can be
measured in a certain period of time. What are these changes?

Formation of precipitate occurs in reactions that
produce insoluble salts. Photograph 7.1 shows before and
after reaction between silver nitrate solution, AgNO3 and
sodium chloride solution, NaCl. In this reaction, silver
chloride, AgCl and sodium nitrate, NaNO3 are formed.
The formation of silver chloride, AgCl can be seen and
the precipitate causes the ‘’ mark to disappear, and the
amount of precipitate can be measured.

Photograph 7.1
The reaction between silver nitrate

solution, AgNO3 and sodium chloride
solution, NaCl

In the chemical manufacturing
factory, a chemical engineer
needs to know accurately
about the rate of reaction that
happens or the duration of time
that is needed for the reaction
to complete. In other words, a
chemical engineer needs to be
proficient in rate of reaction.

Chemistry& Us

221

Rate of Reaction CHAPTER 7
Decrease in the mass of the reactants also occurs in reactions
that produce gases. Photograph 7.2 shows the reaction between
nitric acid, HNO3 and limestone, CaCO3 that produces calcium
nitrate, Ca(NO3)2, carbon dioxide, CO2 and water, H2O.
The loss in the mass of limestone can be measured by using an
electronic balance.

Photograph 7.2
The reaction between nitric

acid, HNO3 and limestone, CaCO3

ChemistryChemistry

Other observable and measurable changes:
• Changes in pressure in reactions involving gases. The change in pressure is measured using a
 pressure meter
• Changes in the electrical conductivity of electrolytes in reactions involving mobile ions. An ammeter is
 used to measure the change in the electrical conductivities in the electrolyte
• Changes in pH values for reactions involving acids or bases in aqueous solutions. A pH meter is used
 to measure the changes in the pH values with time

Activity 7.1
Aim: Determining the time for reaction with reference to some observable and measurable changes.
Materials:  Zinc powder, Zn, 0.1 mol dm–3 sulphuric acid, H2SO4, marble chips, CaCO3,

2.0 mol dm–3 nitric acid, HNO3, potassium iodide powder, KI, lead(II) nitrate
powder, Pb(NO3)2 and distilled water

Apparatus: Retort stand with clamp, burette, basin, 250 cm3 conical flask, 10 cm3 and 100 cm3
measuring cylinders, rubber stopper, delivery tube, electronic balance, stopwatch,
cotton wool, petri dish, weighing bottle, filter funnel, ruler and filter paper

Increase in volume of gases occurs for reactions that
produce gases. Photograph 7.3 shows the reaction between
hydrochloric acid, HCl, and magnesium, Mg. In this
reaction, magnesium chloride, MgCl2 and hydrogen gas, H2
are produced. The hydrogen gas, H2 is collected and the
volume of the gas measured using a gas syringe.

Photograph 7.3
The reaction between hydrochloric

acid, HCl and magnesium, Mg

220

Interaction between MattertheMe 3
Reaction between zinc, Zn and sulphuric acid, H
2

SO
4

Procedure:

1. Add 20 cm3 of 0.1 mol dm-3 sulphuric acid, H2SO4 into a conical flask.
 2. Fill a burette with water and invert it into a basin of water. Clamp the burette vertically.
 3. Adjust the water level in the burette so that the level of water is at the 50 cm3 mark.
 4. Arrange the apparatus as in Figure 7.2.

Figure 7.2

5. Add 5 g of zinc powder, Zn into the conical flask that contains
sulphuric acid, H2SO4.

6. Immediately close the conical flask with the rubber stopper
that is connected to the delivery tube. Start the stopwatch.

7. Record the burette reading at 0.5 minute intervals for
  5 minutes.
 8. Record your results in Table 7.1 given below.

Results:

Table 7.1

Time (minute) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Burette reading (cm3) 50.00

Volume of gas (cm3) 0.00

Discussion:

1. State the observable changes and the measurement made in the activity.
 2. Name the gas released.
 3. Write a chemical equation for the reaction that occurred.
 4. How would you know that the reaction is completed?

Conical flask

Delivery  tube

Hydrogen
gas, H2

Burette

Basin

Water

Sulphuric acid, H2SO4

Zinc, Zn

Make sure the extension on
the apparatus is tight so that
the released gas flows to
the burette.

Safety Precaution

221

Rate of Reaction CHAPTER 7
Reaction between nitric acid, HNO
3

and marble chips, CaCO
3

Procedure:

1. Put 100 cm3 of 2.0 mol dm–3 nitric acid, HNO3 into
a conical flask.

2. Close the mouth of the conical flask loosely with
cotton wool.

3. Set up the apparatus as shown in Figure 7.3.
 4. Add 10 g of marble chips, CaCO3 into the conical flask.
 5. Immediately close the conical flask and start the stopwatch.
 6. Record the reading of the electronic balance at intervals of 30 seconds.
 7. Observe the changes that occur in the conical flask and record all observations.
 8. Record your data in a table.

Discussion:

1. State the observable changes that was recorded in the activity.
 2. Why does such a change occur? Explain your answer with the aid of a suitable chemical equation.
 3. How would you know that the reaction is completed?

Reaction between potassium iodide solution, KI and lead(II) nitrate solution, Pb(NO
3

)
2

Procedure:

1. Using separate weighing bottles, weigh 2 g of
potassium iodide powder, KI and 2 g of lead(II)
nitrate powder, Pb(NO3)2 by using two
different bottles.

2. Pour distilled water into the petri dish to a depth
of 0.5 cm.

3. Add the potassium iodide powder, KI into the water at the edge of the petri dish.
 4. Add lead(II) nitrate powder, Pb(NO3)2 diagonally across from the potassium iodide powder, KI

as shown in Figure 7.4.
 5. Start the stopwatch immediately.
 6. Record the time when the reaction is completed, that is, when no more precipitate is formed.
 7. Filter the contents in the petri dish and wash the precipitate with distilled water.
 8. Dry and weigh the precipitate.
 9. Record your data in a table.
Discussion:

1. What is the colour of the precipitate formed?
 2. Write an equation for the reaction that occurred.

Figure 7.3

Nitric
acid, HNO3

Cotton wool

Marble
chips, CaCO3

ON
OFF g Electronic

balance

Figure 7.4

Potassium
iodide, KI

Distilled water

Petri dish

Lead(II)
nitrate, Pb(NO3)2

Prepare a complete report after carrying out this activity.

Determine the time of reaction based on the observable and measurable changes shown
through Activity 7.1. How would you determine the rate of reaction?

220

Interaction between MattertheMe 3
Average Rate of Reaction and Instantaneous Rate of Reaction

There are two types of rate of reaction, the average rate of reaction and instantaneous rate of
reaction. The analogy for the average of reaction and instantaneous rate of reaction is shown
in Figure 7.5.

Figure 7.5 Analogy of average rate of reaction and instantaneous rate of reaction

The average rate of reaction is the average value for the rate of reaction that occurs in a
particular time interval. The following explains the way to calculate the average rate of reaction for
reactions that release gases.

The overall average rate of reaction

=
Total volume of gas collected

Time taken

= V
t  cm3 s-1

The average rate of reaction for the first t1 seconds

=

Total volume of gas collected in the
first t1 seconds

Time taken

= V1 − 0
t1 − 0  cm3 s-1

= V1

t1
 cm3 s-1

Figure 7.7 The average rate of reaction
for the first t1 seconds

Figure 7.6 The overall average rate
of reaction

A car intends to travel for 400 km. Due to the
ever changing traffic conditions, the driver is
not able to maintain a constant speed and took
4 hours to reach the destination. The average
speed of the car is 100 km hour–1. This is
equated as the average rate of reaction.

A police officer aims the speed camera in the
direction of the car because it is travelling at
a speed above the speed limit. At that instant,
the camera recorded a speed of 140 km hour–1.
The speed at that moment is equated to the
instantaneous rate.

Reaction
stops here

Vo
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m
e

of
 g

as
  (

cm
3 )

Time (s)
0

V

t

Vo
lu

m
e

of
 g

as
  (

cm
3 )

Time (s)

0

V1

t1

221

Rate of Reaction CHAPTER 7
Figure 7.9 Methods to calculate the instantaneous rate of reaction

Draw a tangent to the curve at
time t.

Calculate the gradient of the tangent to the curve.

Use the tangent to complete a vertically-angled
triangle.

Rate of reaction at time t
= Gradient of the tangent at time t

= ΔV
Δt

= V2 − V1

t2 − t1
 cm3 s-1

The instantaneous rate of reaction is the rate of reaction at a particular point of time.
It is determined from the experimental data by plotting a graph of changes in the quantity of the
reactants or products against time, and measuring the tangent gradient to the curve at that point
of time. Figure 7.9 shows the way to calculate the instantaneous rate of reaction.

The average rate from t1 to t2

=
Total volume of gas collected from t1 to t2

Time taken

= V2 − V1

t2 − t1
 cm3 s-1

Figure 7.8 The average rate of
reaction from t1 to t2

Vo
lu

m
e

of
 g

as
 (c

m
3 )

Time (s)

0

V2

V1

t2t1

Vo
lu

m
e

of
 g

as
  (

cm
3 )

Time (s)

Tangent

0 t

Vo
lu

m
e

of
 g

as
 (c

m
3 )

Time (s)
0 t

Vo
lu

m
e

of
 g

as
 (c

m
3 )

Time (s)
0 t1 t2t

V2

V1

The triangle can be
drawn in various sizes.
The bigger the triangle,
the more accurate it
can be to determine the
tangent gradient.

Method 1

Method 3

Method 2

220

Interaction between MattertheMe 3
Activity 7.2
Determining the average rate of reaction and instantaneous rate of reaction

Answer the following questions based on the data obtained from Activity 7.1.
 1. For the reaction between zinc, Zn and sulphuric acid, H2SO4:

(a) Plot a graph of gas volume against time.
(b) Calculate the following average rates of reaction:

(i) For the first minute
(ii) For the fifth minute
(iii) For the overall reaction

(c) Based on the graph plotted, calculate the rate of reaction at the following time:
(i) At the first minute
(ii) At the third minute
(iii) At the end of the reaction

2. For the reaction between potassium iodide solution, KI and lead(II) nitrate solution, Pb(NO3)2:
(a) Calculate the average rate of reaction.
(b) Can you determine the rate of reaction at 30 seconds? Explain.

A student adds magnesium carbonate crystals, MgCO3 until excess into sulphuric acid, H2SO4.
The volume of carbon dioxide, CO2 released is collected in a gas syringe and the volume of gas
recorded in Table 7.2 for 1 minute intervals for 10 minutes.

Table 7.2

Time (minute) 0 1 2 3 4 5 6 7 8 9 10

Volume of gas (cm3) 0 25 40 51 58 63 68 70 70 70 70

(a) Based on Table 7.2, plot a graph of the volume of gas against time.
(b) Calculate the following average rate of reactions:

(i) For the fifth minute
(ii) For the overall reaction

(c) Based on the plotted graph, calculate the rate of reaction for the second minute.

Example 1

To
ta

l m
as

s o
f

re
ac

ta
nt

s (
g)

Time (s)

Method to draw the
tangent gradient

0 t

For reactions that involve a decrease in the total mass of
the reactants, a graph as shown in Figure 7.10 is obtained.

Figure 7.10 The instantaneous rate of
reaction that involves the
decreasing of reactants

Solving Numerical Problems Based on Rate of Reactions

221

Rate of Reaction CHAPTER 7
Solution

(a)

(b) (i) Average rate of reaction for the 5th minute

= Total volume of gas collected from the 4th minute to the 5th minute
Time taken

= (63 – 58) cm3

(5 – 4) minute

= 5 cm3

1 minute

= 5 cm3 minute–1

(ii) The overall average rate of reaction

= Total volume of gas collected
 Time of reaction

= 70 cm3

7 minute

= 10 cm3 minute–1

(c) The rate of reaction at the second minute
 = Gradient of the tangent to the curve at the second minute

= ΔV
Δt

= (64 – 20) cm3

(4 – 0.2) minute
 = 11.58 cm3 minute–1

The average rate of reaction
from the 4th to the 5th minute.

The reaction ends at the 7th
minute and not 10th minute.

0
2 4 6 8

20

40

60

∆ t

∆ V

Vo
lu

m
e

of
 g

as
 (c

m
3 )

10
Time (minute)

220

Interaction between MattertheMe 3
Yourself
TestTest

7.1

1. Explain the meaning of rate of reaction.
 2. Classify the following reactions as fast or slow:

(a) Photosynthesis  (c) Rusting of iron gate
(b) Combustion of petrol in car engines (d) Explosion at oil factory

3. State the observable and measurable change(s) to determine the rate of reaction in the
following examples of reactions:
(a) 2HCl(aq) + CaCO3(s) ˜ CaCl2(aq) + H2O(l) + CO2(g)
(b) H2SO4(aq) + Na2S2O3(aq) ˜ Na2SO4(aq) + H2O(l) + SO2(g) + S(s)
(c) 2SO2(g) + O2(g) ˜ 2SO3(g)
(d) H+(aq) + OH–(aq) ˜ H2O(l)

4. Metals react with acids at different rates.

Metal + Acid → Salt + Hydrogen gas

Three different metals, P, Q and R react separately with 100 cm3
of acid. The time taken to collect 50 cm3 of hydrogen gas for
each of the metal is recorded in Table 7.4
(a) Calculate the average rates of reaction for each of the metal with acid.

(b) Based on your answer in 4(a), arrange the three metals in order of descending reactivity.
Explain your answer.

Table 7.4

Metal Time (s)
P 60
Q 95
R 20

Activity 7.3
Solving numerical problems related to rate of reactions

In the presence of manganese(IV) oxide, MnO2, hydrogen peroxide, H2O2 decomposes to water and
oxygen. The oxygen gas released is collected in a gas syringe and the volume recorded at intervals
of 0.5 minute. The data collected is shown in Table 7.3.

Table 7.3

Time
(minute) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Volume of
gas (cm3) 0.0 13.5 22.0 28.0 33.0 37.0 40.5 43.0 45.0 47.0 48.0 49.0 50.0 50.0 50.0

1. Based on Table 7.3, plot a graph of volume of gas against time.
 2. Calculate the following average rate of reaction:

(a) For the first minute
(b) For the fifth minute
(c) For the whole reaction

3. Calculate the rate of reaction at the following time:
(a) 1.5 minute (b) 4.0 minute

CT

221

Rate of Reaction CHAPTER 7
Figure 7.11 Total surface area of different sizes of reactant

For a fixed mass, the powdered form has a larger total surface area than the original pieces of
the solid. Experiment 7.1 shows the effect of size of reactants on the rate of reaction.

Experiment 7.1

Aim:  To study the effect of size of reactants on the rate of reaction.
Problem statement:  How can size of reactant affect the rate of reaction?
Hypothesis: The smaller the size of the marble chips, CaCO3, the higher the rate of reaction.
Variables:

(a) Manipulated : Size of marble chips, CaCO3
(b) Responding : Rate of reaction
(c) Fixed : Mass of marble chips, CaCO3, temperature, volume and concentration of

hydrochloric acid, HCl
Materials: 0.1 mol dm–3 hydrochloric acid, HCl, large pieces of marble chips, CaCO3 and small

pieces of marble chips, CaCO3
Apparatus: Conical flask 250 cm3, retort stand with clamp, burette, basin, 100 cm3

measuring
cylinder, rubber stopper, delivery tube, electronic balance and stopwatch

Total surface area
= 24 cm2

Total surface area
= 4 × 10 cm2

= 40 cm2

Total surface area
= 2 × 16 cm2

= 32 cm2

1 cm2 cm
2 cm 2 cm

2 cm
2 cm

cut

1 cm
2 cm

1 cm
cut

Different chemical substances have different chemical properties.
As a result, different chemicals have different reactions and occur at
different rates. What are the factors that affect the rate of reactions?

Size of Reactants

Solid reactants can undergo change in sizes. A piece of marble
chip can be cut into smaller pieces. The total surface area of all the
smaller pieces is larger than the total surface area of the original
piece of marble as shown in Figure 7.11

Factors Affecting Rate of Reactions7.2

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
7.2.1 Investigate factors

affecting the rate of
reactions through
experiment, based on:

•	 Size	of	reactants
	 •	 Concentration
	 •	 Temperature
	 •	 Presence	of	catalyst

220

Interaction between MattertheMe 3
Procedure:

1. Put 80 cm3 of 0.1 mol dm-3 hydrochloric acid,
  HCl into a conical flask.
 2. Fill the burette with water and invert it

into a basin filled with water. Clamp the
burette vertically.

3. Adjust the water level in the burette so that
the water level reading is 50 cm3.

4. Set up the apparatus as shown in Figure 7.12.
 5. Weigh 5 g of large pieces of marble chips, CaCO3 and

add them into the conical flask.
 6. Immediately close the conical flask with the rubber stopper

which is connected to a delivery tube. At the same time,
start the stopwatch.

7. Slowly swirl the conical flask throughout the experiment.
 8. Record the burette reading at intervals of 30 seconds until

the burette is completely filled with gas.
 9. Repeat steps 1 to 8 by using smaller pieces of 5 g of marble chips, CaCO3.
 10. Record all the data in table form.

Interpreting data:

1. Based on the data obtained, plot two graphs of volume of gas against time on a same set of axis.
 2. Based on the graph, determine:

(a) The tangent gradient at t = 0 (initial rate of reaction).
(b) The time taken for the complete reaction.

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

231

Prepare a complete report after carrying this experiment.

Concentration

The concentration of a solute in a solution can be changed. The concentration of the solution can
be changed by adding solvent or solute.

Low concentration High concentration

Adding
solvent

Adding
solute

Figure 7.13 Concentration of solution

What is the effect of concentration of reactant on the rate of reaction?

Acids are corrosive. Wear
gloves and safety glasses
when handling acids.

Figure 7.12

Conical
flask

Delivery tube

Carbon
dioxide
gas, CO2

Burette

Basin
Water

Hydrochloric
acid, HCl

Marble chips, CaCO3

221

Rate of Reaction CHAPTER 7
Aim: To investigate the effect of concentration of reactants on the rate of reaction.
Problem statement: How does the concentration of the reactants affect the rate of reaction?
Hypothesis: The higher the concentration of sodium thiosulphate solution, Na2S2O3, the shorter

the time taken for the ‘’ mark to disappear from view.
Variables:

(a) Manipulated : Concentration of sodium thiosulphate solution, Na2S2O3
(b) Responding : Time taken for the ‘’ mark to disappear from view
(c) Fixed : Temperature, total volume of mixture, concentration and volume of sulphuric

acid, H2SO4 and the size of the conical flask
Materials: 1.0 mol dm–3 sulphuric acid, H2SO4, 0.2 mol dm–3 sodium thiosulphate solution, Na2S2O3,

distilled water and white piece of paper with a ‘’ mark at the centre
Apparatus: 150 cm3 conical flask, stopwatch, 10 cm3 and 50 cm3 measuring cylinders
Procedure:

1. Put 45 cm3 of 0.2 mol dm–3 sodium thiosulphate
solution, Na2S2O3 into a conical flask.

2. Place the conical flask on the ‘’ mark on the white
paper as shown in Figure 7.14.

3. Swiftly, pour 5 cm3 of 1.0 mol dm–3 sulphuric
acid, H2SO4 into the conical flask carefully and at
the same time start the stopwatch.

4. Swirl the conical flask gently and place it again on
the ‘’ mark.

5. Observe the ‘’ mark vertically from the mouth of the conical flask.
 6. Stop the stopwatch once the ‘’ mark disappears from view. Record the time taken.
 7. Repeat the experiment by using 0.2 mol dm–3 sodium thiosulphate solution, Na2S2O3 that

has been diluted with distilled water as given in Table 7.5. The volume of 1.0 mol dm–3 sulphuric
acid, H2SO4 is fixed at 5 cm3.

8. Record all data in Table 7.5.

Results:

Table 7.5

Experiment I II III IV V

Volume of sodium thiosulphate solution, Na2S2O3 (cm3) 45 40 30 20 10

Volume of distilled water (cm3) 0 5 15 25 35

Volume of sulphuric acid, H2SO4 (cm3) 5 5 5 5 5

Total volume of mixture (cm3) 50 50 50 50 50

Time taken for the ‘’ mark to disappear from view (s)

Experiment 7.2

Figure 7.14
White paper

‘  ’ mark

Sodium thiosulphate,
Na2S2O3
+ Sulphuric acid,
H2SO4

220

Interaction between MattertheMe 3
Prepare a complete report after carrying out this experiment.

Temperature

Most reactions occur faster at high temperatures, that is, the rate of reaction increases with
increasing temperature. For reactions that occur at room temperature, each increase of 10 °C will
increase the reaction rate by two times.

Interpreting data:

1. The concentration of dilute sodium thiosulphate solution, Na2S2O3 is calculated using the
formula  M1V1 = M2V2.

M1 = The original concentration of sodium thiosulphate solution, Na2S2O3
V1 = The volume of sodium thiosulphate solution, Na2S2O3 used
M2 = Concentration of the dilute sodium thiosulphate solution, Na2S2O3
V2 = Volume of the dilute sodium thiosulphate solution, Na2S2O3

Use the given formula and the data collected to calculate the concentration of the dilute
sodium thiosulphate solution, Na2S2O3.

2. In the experiment, the rate of reaction is inversely proportional to the time taken for the ‘’

mark to disappear from view. Thus, rate of reaction = 1
time . Use this formula and the data

collected to calculate the rate of reaction for all the five experiments.
 3. Record all answers from (1) and (2) in Table 7.6.

Table 7.6

Experiment I II III IV V

Concentration of dilute sodium thiosulphate,
Na2S2O3 solution (mol dm–3)

Rate of reaction, 1
time  (s–1)

4. Use the data in Table 7.6 to plot a graph of rate of reaction, 1
time  against concentration of

sodium thiosulphate solution, Na2S2O3, M2.
 5. Based on the graph, state the relationship between rate of reaction and concentration of

sodium thiosulphate solution, Na2S2O3.

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Discussion:

1. Why does the solution in the conical flask turn cloudy?
 2. Name the substance that causes the solution to turn cloudy.
 3. The ‘’ mark disappears from view when the solution in the conical flask reaches a certain

level of cloudiness. What are the steps required in this experiment so that the same level of
cloudiness is achieved in all the five experiments?

4. What are the changes being measured in the experiment to determine the rate of reaction?

221

Rate of Reaction CHAPTER 7
Experiment 7.3

Aim: To investigate the effect of temperature on the rate of reaction.
Problem statement:  How does temperature affect the rate of reaction?
Hypothesis:  The higher the temperature of the sodium thiosulphate solution, Na2S2O3, the shorter

the time taken for the ‘’ mark to disappear from view.
Variables:

(a) Manipulated : Temperature of sodium thiosulphate solution, Na2S2O3
(b) Responding : Time taken for the ‘’ mark to disappear from view
(c) Fixed : Volume and concentration of sulphuric acid, H2SO4

Materials: 1.0 mol dm–3 sulphuric acid, H2SO4, 0.2 mol dm-3 sodium thiosulphate solution, Na2S2O3
and a piece of white paper with an ‘’ mark in the middle

Apparatus: 150 cm3 conical flask, 10 cm3 and 50 cm3 measuring cylinders, stopwatch,
thermometer, Bunsen burner, wire gauze and tripod stand

Procedure:

1. Put 50 cm3 of 0.2 mol dm–3 sodium thiosulphate solution, Na2S2O3 into a conical flask.
  Leave it for 5 minutes.
 2. Record the temperature of the 0.2 mol dm–3 sodium thiosulphate solution, Na2S2O3.
 3. Place the conical flask on the ‘’ mark of the white paper.
 4. Quickly, add in 5 cm3 of 1.0 mol dm–3 sulphuric acid, H2SO4 into the conical flask carefully.
  At the same time, start the stopwatch.
 5. Swirl the conical flask gently and place it again on the ‘’ mark.
 6. Observe the ‘’ mark vertically from the mouth of the conical flask.
 7. Stop the stopwatch once the ‘’ mark disappears from view.
 8. Record the time taken when the ‘’ mark disappears from view.
 9. Repeat steps 1 until 8 by using 50 cm3 of 0.2 mol dm–3 sodium thiosulphate solution, Na2S2O3

that has been heated to 40 oC, 45 oC, 50 oC, and 55 oC.
Interpreting data:

1. Use the data obtained to plot a graph of rate of reaction, 1
time  against temperature of

sodium thiosulphate solution, Na2S2O3.
 2. Based on the graph, state the relationship between rate of reaction and the temperature of

sodium thiosulphate solution, Na2S2O3.
Conclusion:

Is the hypothesis acceptable? What is the conclusion of the experiment?
Discussion:

1. Write the ionic equation for the reaction between sodium thiosulphate solution, Na2S2O3 and
sulphuric acid, H2SO4.

2. Can sulphuric acid, H2SO4 be replaced with hydrochloric acid, HCl? Explain.

Prepare a complete report after carrying out this experiment.

220

Interaction between MattertheMe 3
Presence of Catalyst

Catalysts are chemical substances that alter the rate of chemical reactions without undergoing any
chemical changes at the end of the reaction. Although the chemical properties of the catalyst does not
change, but its physical properties can change. For example, a lump of catalyst can turn into powder.

Catalysts do not change the quantity of products. Does the addition of a catalyst increase the
rate of reaction?

Experiment 7.4

Aim:  To investigate the effect of catalyst on the rate of reaction.
Problem statement:  How does the presence of catalyst affect the rate of reaction?
Hypothesis:  Presence of catalyst increases the rate of reaction.
Variables:

(a) Manipulated : Presence of catalyst
(b) Responding : Rate of reaction
(c) Fixed : Mass of manganese(IV) oxide, MnO2, temperature and volume of hydrogen

peroxide solution, H2O2

Materials: 20-volume hydrogen peroxide solution, H2O2, manganese(IV) oxide powder, MnO2
and distilled water

Apparatus:  10 cm3 measuring cylinder, test tubes, test tube rack, glowing wooden splinter, filter
funnel, filter paper, 150 cm3 beaker, spatula and electronic balance

Procedure:

1. Label two test tubes as I and II.
 2. Put 5 cm3 hydrogen peroxide solution, H2O2 into test tube I
  and test tube II separately.
 3. Place the two test tubes in the test tube rack.
 4. Add 0.5 g manganese(IV) oxide powder, MnO2 into test tube II.
  Place a glowing wooden splinter into the mouth of both test tubes quickly.
 5. Observe the changes that occur to the wooden splinter and record your observations.
Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?
Discussion:

1. What are the changes observed and measured in this experiment?
 2. Explain how the observation in (1) can assure your hypothesis.

Concentration of
hydrogen
peroxide
solution

http://bit.ly/
2W0iIKD

Prepare a complete report after carrying out this experiment.

ChemistryChemistry

The mass of catalyst does not change before and after the reaction. You can compare the mass of
manganese(IV) oxide, MnO2 before and after Experiment 7.4 for confirmation.

221

Rate of Reaction CHAPTER 7
Diagram 7.15 summarises the effect of concentration, size
of reactants, temperature and catalyst on the rate of reaction.

ChemistryChemistry

Pressure is another factor that affects the rates of reactions. Increasing the
pressure on reactions involving gases will affect the rate of reaction. When a
gas is compressed at constant temperature, the gas particles are pushed into
a smaller volume of space. Increasing pressure, increases the concentration
of the gas and the rate of reaction. Changes in pressure does not affect the
rate of reaction involving solids and liquids reactants as the volume does not
change with pressure.

Increasing
pressure

Acronym CSTP can help
you to remember the
factors that affect the rate
of reaction.

Figure 7.15 Factors affecting rates of reactions

Reactive metals such as potassium reacts with water to release hydrogen gas.

Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

Two experiments are carried out to determine the rate of reaction between 0.7 g of calcium and
200 cm3 of water at different temperatures. Experiment I is carried out at room temperature.
In experiment II, the temperature of water is increased by 10 °C. The diagram below shows the
graph of volume of hydrogen gas against time for experiment I.

V
ol

um
e

of
hy

dr
og

en
 g

as
  (

cm
3 )

Time (s)0

420

I

(a) What is the total volume of hydrogen gas produced in experiment II?
 Explain your answer.
(b) Copy the graph above and sketch the curve for experiment II.
(c) What is the effect of temperature on the rate of reaction?

Example 2

Rate of
reaction

increasesTemperature increases

Size of solid reactants decreases

Presence of catalyst

Concentration of reactants increases

Ti spLiteracy

Effect of pressure on
the rate of reaction

http://bit.ly/33zfz6O

220

Interaction between MattertheMe 3
Solution

(a) Total volume of hydrogen gas produced in experiment II = 420 cm3.
 The quantity of reactants (calcium and water) is the same in both experiments.
 So, the results of (hydrogen gas) reaction must be the same.
(b)

V
ol

um
e

of
hy

dr
og

en
 g

as
 (c

m
3 )

Time (s)0

420

I

II

(c) Increase in water temperature increases the rate of reaction.

Gastric is caused by the production of too much acid in the stomach. Doctors use antacid
tablets to neutralise the acid in the stomach. Table 7.7 shows the time taken by each antacid
tablet to react completely in excess hydrochloric acid, HCl under different conditions.

Table 7.7

Experiment
Volume of

hydrochloric acid,
HCl (cm3)

Concentration of
hydrochloric acid,

HCl (mol dm‒3)

Temperature of
hydrochloric acid,

HCl (oC)

Time of
reaction (s)

I 50 1.0 30 120

II 50 2.0 30 60

III 100 2.0 30 60

IV 50 2.0 40 30

(a) Why the time of reaction is different for experiment I and II?
(b) Which of the following experiment shows that the change in volume of hydrochloric

acid, HCl does not affect the rate of reaction?
(c) Why is the rate of reaction for experiment IV higher than experiment II?
(d) Other than temperature and concentration of the hydrochloric acid, HCl, what changes can

be made to increase the rate of reaction in experiment I?

Solution

(a) Experiment I uses 1.0 mol dm–3 hydrochloric acid, HCl while experiment II uses
 2.0 mol dm–3 hydrochloric acid, HCl. The concentration of hydrochloric acid is different.
(b) Experiment II and III.
(c) The temperature of the hydrochloric acid, HCl in experiment IV is higher than in

experiment II.
(d) The size of the antacid tablet. Crush the tablet into smaller pieces so as to increase the total

surface area.

Example 3

221

Rate of Reaction CHAPTER 7
Activity 7.4
Discussing the solution involving the rate of reactions and determine

the variables involved in the reactions

As a group, solve the following problems:
 1. Figure 7.16 shows the graph of volume of carbon dioxide

against time for the two experiments, I and II.
  Table 7.7 shows the conditions of the two experiments.
 Table 7.7

Experiment Reactants

I 1.0 g of marble chips, CaCO3 + 50 cm3 of 0.5 mol dm–3
hydrochloric acid, HCl at room temperature

II Marble, CaCO3 + 50 cm3 of 0.5 mol dm–3 hydrochloric
acid, HCl

Suggest two ways to carry out experiment II so that a similar graph as in Figure 7.16 can be
obtained. State all the variables involved.

2. Hydrogen peroxide, H2O2 decomposes slowly at room temperature to produce water and
oxygen. The decomposition of hydrogen peroxide, H2O2 can be accelerated by the presence of
a catalyst. Three experiments are carried out to determine the effect of three different catalysts
on the complete decomposition of 50 cm3 of 10-volume hydrogen peroxide solution, H2O2.
Table 7.8 shows the results of the experiments.

Table 7.8

10 20 30 40 50 60
Volume of oxygen gas collected (cm3)

Manganese(IV) oxide, MnO2 57 82 93 100 100 100

Copper(II) oxide, CuO 12 19 25 28 30 31

Iron, Fe 33 47 55 58 59 60

Type of catalyst
Time(s)

CT

Volume of carbon dioxide gas (cm3)

Time (s)
0

I

II

Figure 7.16

Adnan carries out an experiment to investigate the
decomposition of hydrogen peroxide, H2O2. He records
the volume of oxygen gas released. At the 5th minute, he
adds one spatula full of black powder into the hydrogen
peroxide solution, H2O2. The diagram shows the graph of
volume of oxygen gas released against time.
(a) What is the effect of the black powder on the rate
 of reaction?
(b) What is the function of the black powder?

Solution

(a) The addition of the black powder increases the rate of reaction.
(b) The black powder acts as a catalyst.

Example 4

Volume of oxygen gas (cm3)

Time (minute)
50 10 15 20

220

Interaction between MattertheMe 3
(a) Write the chemical equation for the decomposition of hydrogen peroxide, H2O2.
(b) Explain briefly how the experiment was conducted. Include the following in
 your explanation:

(i) Problem statement
(ii) Hypothesis
(iii) All the variables
(iv) Diagram for the set-up of the apparatus

(c) Which catalyst is more effective in speeding up the rate of decomposition of hydrogen
peroxide, H2O2? Explain your answer.

Yourself
TestTest

7.2

1. The rate of reaction is affected by various factors.
(a) State four factors that would affect the rate of reaction.
(b) Zinc, Zn reacts with excess sulphuric acid, H2SO4 according to the following equation:

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)

State four ways to speed up the reaction. In your answer, state the manipulated and the
fixed variables.

2. Four experiments to study the reaction between 2 g of marble, CaCO3 with 15 cm3 of
hydrochloric acid, HCl is shown in Figure 7.17.

1.0 mol dm–3

hydrochloric acid, HCl
+ water at 30 °C

5.0 mol dm–3

hydrochloric acid, HCl
+ water at 30 °C

1.0 mol dm–3

hydrochloric acid, HCl
+ water at 60 °C

5.0 mol dm–3

hydrochloric acid, HCl
+ water at 60 °C

Experiment I Experiment II

Lumps of
marble, CaCO3

Experiment III

Powdered
marble, CaCO3

Experiment IV

Figure 7.17

(a) State the variable that can be observed and measured to determine the rate
of reaction.

(b) What is the manipulated variable in the experiment?

(c) Which experiment has the highest initial rate of reaction? Explain your answer.

221

Rate of Reaction CHAPTER 7
The	Size	Factor

Rate of reactions are important in daily life whether
at home or in industry. Have you ever wondered how to cook
food fast?

Application of Factors that
Affect the Rate of Reaction
in Daily Life

7.3

Action of medicines

Antacid tablets are used to treat gastric. Doctors advise patients to chew the tablet instead of
swallowing. Breaking up the tablet into smaller pieces increases the total surface area exposed
and increases the rate of reaction between the medicine and the acid in the stomach.

Photograph 7.4 Potato strips

Activity 7.5
Solving problems in various daily life activities

1. Carry out the Role-Play activity.
 2. Collect information from various sources to solve the following problems:

(a) How to cook food fast?
(b) How to maintain the freshness of milk?
(c) How to remove a blood stain on a shirt?

3. Discuss and prepare the script with suitable equipment.
 4. Present your group performance in front of the class within the time allocated.

CT

Corrosion due to acid rain

Buildings made of iron that are located near the industrial areas will corrode fast due to acid
rain. The atmosphere around industrial areas contains a high concentration of sulphur dioxide.
When the concentration of the acidic pollutants increases, the level of acid rain increases and
the rate of corrosion increases.

Concentration	Factor

Cooking food

Potatoes are cut into thin slices or long strips so that it can be cooked
faster. Thin slices or long strips increases the total surface area exposed
to the cooking oil compared to uncut potatoes.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
7.3.1 Explain with examples

the application of
factors that affect the
rate of reaction in
daily life

Century
Skills21st

220

Interaction between MattertheMe 3
Cleaning

Washing clothes using detergent powder and hot water combines
two factors that increase the rate of reaction. The process of
washing clothes will be even quicker in this situation.

Cooking food

Other than decreasing the size, food also cooks faster at high
temperatures. Water boils at 100 °C while cooking oil would not boil
even the temperature reaches 180 °C. Therefore, frying food in oil will cook the food even faster.

Temperature	Factor

Combustion of petrol in car engines

Petrol vapour and air are compressed in the car engine combustion
chamber before being burned. The compression increases the
concentration of the petrol vapour allowing the petrol to burn very
quickly until it explodes. The energy released from the combustion
of petrol will make the car move. Photograph 7.5

Combustion of petrol in
a car engine

Photograph 7.6  Washing clothes

Catalytic converter

Modern cars are fitted with catalytic converters as shown in
Photograph 7.7 to cut down atmospheric pollution. Exhaust gas
from car engines contains pollutants. Figure 7.18 shows how
catalytic converters change pollutants into non-harmful products
that are safe to be released into the atmosphere in the presence of
platinum catalyst, Pt.

Unburned hydrocarbon, CxHy
Carbon monoxide, CO
Nitrogen oxide, NOx

Platinum catalyst, Pt

Catalytic converter

Water, H2O
Carbon dioxide, CO2
Nitrogen, N2

Figure 7.18

Making alcohol
Ethanol, C2H5OH, is the main ingredient in alcoholic drinks. Ethanol is produced through the
fermentation of glucose with the help of enzyme in yeast as a catalyst at 37 °C.

Photograph 7.7  Catalytic
converter

Catalyst	Factor

221

Rate of Reaction CHAPTER 7
Discussing the application of the knowledge on the factors that affect

the rate of reactions in daily activities

1. Carry out the activity in groups.
 2. Find information from various reading sources and the internet related to the application of

the knowledge on the factors that affect the rate of reactions in the following daily activities.
(a) Burning of coal
(b) Food storage in the refrigerator
(c) Cooking using pressure cooker
(d) Fermentation process in the making of ‘tapai’

3. Based on the information collected, start a forum titled ‘Rate of Reaction in Daily Life’.

Activity 7.6
CT

Yourself
TestTest

7.3

1. Fill in the blanks.
(a) Meat cooks faster if it is cut into  sizes.
(b) In the refrigerator, the  temperature decreases the growth of bacteria that

causes food decay.
(c) Food cooks faster in a pressure cooker because of high .
(d) Coal burns faster in small chips because of the large surface area that is .

2. In industry, ammonia, NH3 is produced by the direct
combination between nitrogen, N2 and hydrogen, H2.
Ammonia, NH3 is used to make nitrogeneous fertilisers.

Figure 7.19 shows the percentage yield of ammonia, NH3
  under different conditions.

(a) State the effect on the percentage yield of
 ammonia, NH3 with increasing:

(i) Temperature (ii) Pressure
(b) Explain the advantages and disadvantages of using 350 °C and 550 °C in the process of

producing ammonia, NH3. How can the disadvantages be overcome?

3. Car exhaust gas contains polluting gases formed from the burning of fossil fuels in the
  car engine.

(a) Name three polluting gases in the car exhaust.
(b) In the car engine, nitrogen, N2 combines with oxygen, O2 to produce nitrogen

monoxide, NO. At room temperature and pressure, this reaction occurs very slow.
 Why can this reaction occur in the car engine?

Figure 7.19

50

10
0

20 550 °C
500 °C
450 °C

400 °C
350 °C

30
40
50
60
70

Pressure (atm)

%
 y

ie
ld

o
f a

m
m

on
ia

, N
H

3

100 150 200 250 300 350 400 450

220

Interaction between MattertheMe 3
According to the kinetic theory of matter, matter is made up of
tiny and discrete particles that are constantly moving; vibrating at
fixed positions for solid, and moving freely for liquids and gasses.
As a result, particles collide with one another.

During collision, transfer of energy occurs. Fast moving
particles transfer some of their energy to slow moving particles
and increases their kinetic energy. This process is repeated with
other particles. As a result, particles do not have the same kinetic
energy and are constantly changing.

The collision theory explains how reactant particles interact
with one another to cause reactions to occur and form products.

According to the collision theory,
•	 reactant	particles	must	collide	with	one	another

for reaction to occur
•	 the	rate	of	reaction	depends	on	the	frequency	of

effective collisions

Not all collisions between reactant particles result in reactions
and the formation of products. Only effective collisions would cause
reactions to occur. To produce effective collisions, the reactant
particles must have energy equal to or more than the activation
energy and collide in the correct orientation.

Activation Energy

Reactant particles need to have enough energy to initiate a
reaction. In other words, activation energy is required to start a
reaction. Activation energy is like an energy barrier that needs to
be overcomed before a reaction can take place. Photograph 7.8
shows the analogy of such a barrier. The energy required for
a horse to overcome the barrier is identical to the activation
energy that the particles require to initiate a reaction.

Reactant particles need to acquire the minimum energy
known as activation energy so as to break the bonds in the
reactant particles and form new bonds in the products.
Different reactions have different activation energy.

Collision Theory7.4

ChemistryChemistry

Collision between particles
with energy less than the
activation energy or in the
wrong orientation is called
an ineffective collision.

LearningLearning
StandardStandard

At the end of the lesson,
pupils are able to:
7.4.1 Describe the
 collision theory
7.4.2 Explain activation

energy using examples
7.4.3 Interpret an energy

profile	diagram	for
exothermic reaction and
endothermic reaction

Collision theory

http://bit.ly/35RRzhl

Photograph 7.8
Analogy of activation energy

221

Rate of Reaction CHAPTER 7
The activation energy is represented by the symbol Ea. In the energy profile diagram, the
activation energy is the difference in energy between the energy level of the reactants and the
energy at the peak of the curve in the graph.

Figure 7.20  Energy profile diagram

In an exothermic reaction, the total energy of the reactants is higher than the total energy of
the products. In an endothermic reaction, the total energy of the products is higher than the total
energy of the reactants.

Collision Orientation

Reactant particles must be in a specific orientation to result in effective collisions. Figure 7.21
shows the collision between reactant particles in the correct orientation to allow old bonds to be
broken and new bonds to form.

Figure 7.21

+ +
←→

If the reactant particles collide in incorrect orientations, the
particles will bounce back and no reaction occurs. Figure 7.22 shows
the collision between reactant particles in the wrong orientation.

Figure 7.22

+ +
←→

Effective Collision and Rate of Reaction

The rate of reaction depends on the rate of successful collisions between the reactant particles.
The higher the frequency of collision between reactant particles with enough energy and in the
correct orientation, the faster the reaction occurs. In other words, the rate of reaction depends on
the frequency of effective collisions.

Energy

Reaction pathway

Reactants

Products

Ea

Energy

Reaction pathway

Reactants
ProductsEa

Collision theory
(Part 2)

http://bit.ly/
35Q8DnZ

Collision theory
(Part 3)

http://bit.ly/
35RRRor

Exothermic reaction Endothermic reaction

220

Interaction between MattertheMe 3
The higher the frequency of effective collisions, the higher the rate of reaction.
The lower the frequency of effective collisions, the lower the rate of reaction.

Effect of Concentration on the Rate of Reaction

Based on Figure 7.23, which has a higher frequency of collision?

Reactant
particles

(a) Low concentration (b) High concentration

Figure 7.23  The effect of concentration of reactants on the rate of reaction

When the concentration of the reactant particles increases,
•	 the	number	of	particles	per	unit	volume	increases
•	 the	frequency	of	collisions	between	particles	increases
•	 the	frequency	of	effective	collisions	between	particles	increases
•	 the	rate	of	reaction	increases

For reactions involving gases, changes in pressure is the same as changing the concentration
of the gas. What is the effect of gas pressure on the rate of reaction?

When the pressure of a gas increases,
•	 the	number	of	particles	per	unit	volume	increases
•	 the	frequency	of	collisions	between	particles	increases
•	 the	frequency	of	effective	collisions	between	particles	increases
•	 the	rate	of	reaction	increases

Effect of Size of Reactant on the Rate of Reaction

When a large piece of a solid reactant is broken up into smaller pieces, the total volume of the
substance remains the same. However, the total surface area of the reactant increases. Figure 7.24
explains the effect of particle size on the rate of reaction.

221

Rate of Reaction CHAPTER 7
The increasing surface
area enables more pink
particles to collide with
the green particles.

Block of solid reactant Small fragments of
solid reactant

Only the outer layer
of the pink particles
of the solid reactants
can collide with the
green particles.

Broken down

Figure 7.24  The effect of size of reactant on the rate of reaction

When the total surface area of the reactant increases,
•	 the	total	surface	area	exposed	to	collision	increases
•	 the	frequency	of	collisions	between	particles	increases
•	 the	frequency	of	effective	collision	increases
•	 the	rate	of	reaction	increases

Effect of Temperature on the Rate of Reaction

When the temperature increases, the rate of reaction increases. This phenomenon is explained
in Figure 7.25.

Figure 7.25  The effect of temperature on the rate of reaction

When temperature increases,
•	 the	kinetic	energy	of	the	reactant	particles	increases
•	more	particles	have	energy	to	overcome	the	activation	energy
•	 the	frequency	of	effective	collisions	between	particles	increases
•	 the	rate	of	reaction	increases

Effect of Catalyst on the Rate of Reaction

A catalyst is involved in a reaction but remains chemically unchanged at the end of the reaction.
The catalyst allows the reaction to occur by providing an alternative pathway with lower activation
energy, Ea as compared to the original activation energy, Ea.

(a)  Low temperature (b) High temperature

Reactant
particles

Temperature
is a measure
of the average
kinetic energy
of the particles.

220

Interaction between MattertheMe 3
Conceptualising the collision theory in reactions that are affected

by temperature, reactant size, pressure, concentration and catalyst

1. Carry out the Gallery Walk activity.
 2. Get the following information from various reading and search the Internet.

(a) Collision theory
(b) Use of the collision theory to explain the effect of the following factors on the rate
 of reaction

3. Discuss with your group members and prepare an interesting presentation.
 4. Present your group’s work in the class. Move in groups to see the works of other groups.
 5. Write two stars and a wish about the works of the other groups on sticky notes and paste on

the work.

Activity 7.7

Exothermic Reaction and Endothermic Reaction

Changes in energy can occur during chemical reactions. Reactions that release heat energy to the
surroundings are called exothermic reactions. Otherwise, reactions that absorb heat energy from
the surroundings are called endothermic reactions. All exothermic reactions or endothermic
reactions have activation energy, Ea that must be overcomed by the reactant particles.

CT

Energy

Reaction pathway

Reactants

Without catalyst

Products

Ea

Ea'
With catalyst

Energy

Reaction pathway

Reactants

Without catalyst

Products
Ea

Ea'

With catalyst

Figure 7.26  The effect of catalyst on the magnitude of the activation energy

In the presence of a catalyst,
•	 the	catalyst	provides	an	alternative	pathway	by	lowering	the	activation	energy
•	more	reactant	particles	can	achieve	the	activation	energy
•	 the	frequency	of	effective	collisions	between	the	particles	increases
•	 the	rate	of	reaction	increases

Exothermic reaction

Key: Ea = Activation energy without catalyst      Ea´ = Activation energy with catalyst

Endothermic reaction

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221

Rate of Reaction CHAPTER 7
Figure 7.27  Energy profile diagram for exothermic reaction and endothermic reaction

The change in energy content that occurs when reactants are changed into products is known
as the heat of reaction and is represented by the symbol ΔH.

Yourself
TestTest

7.4

1. The Kinetic Theory of Matter states that the particles in matter are constantly moving.
Mark (3) for true statements and (7) for false statements.
(a) At constant temperature, all particles move with the same velocity.

(b) Particles in solids are moving freely.

(c) Collisions between particles are random.

(d) The kinetic energy of particles increases with increasing temperature.

2. Scientists use the collision theory to explain how chemical reactions occur. State two
important conditions for effective collisions.

3. Catalysts can help to speed up chemical reactions. How does a catalyst speed up a
chemical reaction?

4. All reactions including exothermic reactions and
endothermic reactions have activation energy that
must be overcome by reactant particles.
(a) What do you understand by the term

activation energy?
(b) Mark and label the activation energy in

Figure 7.28.
(c) Complete the following statements:

(i) Exothermic reactions  heat
to .

(ii) Endothermic reactions  heat
from .

Reaction pathway

Energy

Reactants

Products
∆H
(Negative)

Ea

Reaction pathway

Energy

Reactants Products

∆H (Positive)

Ea

Figure 7.28

Reaction pathway

Energy

Reactants Products

You will learn more
about exothermic
and endothermic
reactions in the topic of
thermochemistry in Form 5.

Exothermic reaction Endothermic reaction
 Ti spLiteracy

220

Interaction between MattertheMe 3
definition

explained by

affected by

Collision Theory

Temperature Presence of catalyst

Frequency of effective collisions between particles
increases, the rate of reaction increases

Reactant particles must collide
with one another

Rate of Reaction

Time (s)0

Tangent gradient
= Instantaneous rate
   of reaction, t1

t2t1

m

Mass of reactants (g)

Average rate =
Δm––Δt

Time (s)0 t2t1

V

Volume of gas released (cm3)

Average rate =
ΔV––Δt

Tangent gradient
= Instantaneous rate
   of reaction, t1

Concept

•	 Concentration of
reactant , rate of
reaction

•	 Number of particles
per unit volume

•	 Size of reactant ,
rate of reaction

•	 Total surface
area exposed to
collision

•	 Temperature , rate
of reaction

•	 Temperature ,
kinetic energy of
particles

•	 Presence of catalyst,
rate of reaction

•	 Alternative pathway
with lower activation
energy, Ea.

Self Reflection

1. What new knowledge have you learned from Rate of Reaction?
 2. Which is the most interesting subtopic in Rate of Reaction? Why?
 3. Give a few examples of the application of Rate of Reaction in daily life.
 4. Rate your performance in Rate of Reaction on a scale of 1 to 10;

1 being the lowest while 10 the highest.
Why would you rate yourself at that level?

5. What can you do to improve your mastery in Rate of Reaction?

https://bit.ly/
32lEzyv

Change in the quantity of reactants or products
Time taken

QuickQuick

http://bit.ly/
33X1ksG

Concentration Size of reactant

221

Rate of Reaction CHAPTER 7
Achievement 7

1. Rate of reaction measures the change in the quantity of reactants or products per unit time.
(a) State three units for measuring the quantity of substances.
(b) For each unit of measurement for the quantity of substances in 1(a), state the

corresponding unit for the rate of reaction.

2. There are chemical reactions that are fast or slow in daily life. Some examples are given
below. Arrange the reactions in the descending order of the speed of reaction.
(a) Banana decaying (d) Combustion of domestic gas
(b) Baking a cake (e) Rusting of iron nails
(c) Boiling eggs

3. A protein-digesting enzyme is used to study the effect of temperature on the rate of protein
digestion in milk. The set-up of the apparatus is shown in Figure 1. The time measured is the
time taken for the enzyme to digest all the protein and the milk becomes clear, that is until
the ‘’ mark is visible. Table 1 shows the results of the experiment.

‘ ’  mark is drawn on a
white paper and put
behind the boiling tube

Milk + enzyme

X

Figure 1

Table 1

Temperature (oC) 15.0 25.0 35.0 45.0 55.0 65.0
Time taken for the ‘’ mark to be visible  (minute) 12.0 7.0 2.5 4.0 7.0 19.0

1
time

(minute–1)

(a) State the changes that are observed and measured.
(b) State the manipulated variable and the fixed variables.
(c) The time of reaction is determined by measuring the time taken for the milk solution to

turn clear.
(i) What is the relationship between the rate of reaction and time?

(ii) Complete Table 1 by calculating the value of 1
time .

(iii) Plot a graph of 1
time  against temperature.

(iv) What conclusion can be formulated based on the graph in (c)(iii)?
 Explain your answer.

220

Interaction between MattertheMe 3
4. The collision theory explains how reactant particles interact for reaction to occur and
products formed.
(a) What are the two main principles of the collision theory?
(b) Dinitrogen monoxide, N2O, known as laughing gas, is produced from the following reaction:

NH4NO3(aq) → N2O(g) + H2O(l) + Heat

(i) Balance the above equation.
(ii) Draw the fully labelled energy profile diagram, including the activation energy, for

the reaction.
(c) Dinitrogen monoxide, N2O reacts with nitrogen monoxide, NO to produce nitrogen, N2

and nitrogen dioxide, NO2.

N2O(g) + NO(g) → N2(g) + NO2(g)

The reactants, dinitrogen monoxide, N2O and nitrogen monoxide, NO have to collide
in the correct orientation to produce effective collisions and for the reaction to occur.
Figure 2 shows the atomic arrangement of the reactants and products.

Dinitrogen
monoxide

Nitrogen
monoxide

Nitrogen

Atom N

Key:

Atom O
Nitrogen
dioxide

Figure 2
 Draw the orientation of the reactant particles, dinitrogen monoxide, N2O and nitrogen

monoxide, NO that results in effective collisions.

CornerEnrichmen

1. 1.0 g marble powder, CaCO3 is added simultaneously to 50 cm3 of hydrochloric acid, HCl of
concentrations 0.5 mol dm_3  and 1.0 mol dm_3. Excess acid is used in each beaker. Which
reaction proceeds fastest? Explain your answer using the collision theory.

2. Acids reacts with metals to produce salt and hydrogen gas. One example of the reaction is
shown below:

Tin + Hydrochloric acid → Tin(II) chloride + Hydrogen

The time of reaction can be obtained by recording the volume of gas released at fixed time
intervals. Plan an experiment to determine the effect of particle size on the rate of reaction.
In your answer, include the followings:

(a) Sketch the set-up of the apparatus
 (b) Volume and concentration of the acid used
 (c) Mass and the physical state of tin used
 (d) Temperature of the reaction
 (e) Procedure of the experiment
 (f) Appropriate graphs
 (g) Explanation on the conclusion obtained

Check   AnswersAnswers

https://bit.ly/
35RsfIt

221

Rate of Reaction CHAPTER 7
8
 Alloy
 Pure metal
 Superconductor
 Glass
 Ceramic
 Composite material

What will you learn?
8.1 Alloy and Its Importance
8.2	 Composition	of	Glass	and	Its	Uses
8.3	 Composition	of	Ceramics	and	Its	Uses
8.4 Composite Materials and Its Importance

CHAPTER

KeywordsKeywords

Manufactured
Substances in
Industry

252
Why is pure aluminium not used to make the body
of	aeroplanes?

What	are	the	two	main	elements	found	in
all	types	of	glass?

What	is	the	property	of	ceramic	that	makes	it
suitable	to	be	used	in	the	construction	of	houses?

Developments in the automobile industry from time to
time has brought about many astounding changes.
 Try to visualise yourself in the cockpit of the most
advanced car in the future. With the help of Artificial
Intelligence (AI), the car can automatically move according
to the driver’s instructions. Besides traditional synthetic
materials, the usage of advanced materials such as nano
materials can lead to the invention of high capability
systems to execute AI programs in the vehicle.
 The University of Kuala Lumpur Malaysian Spanish
Institute, UniKL MSI has successfully found a way to
produce nanoparticles at a low cost. This ideal innovation
indirectly leads to the invention of the most advanced car.

Bulletin

253
Alloy and Its Importance8.1

Photograph 8.1
The National Monument

The National Monument was built in
1966 using alloys. What is an alloy?

An alloy is a mixture of two
or more elements where the main
element is a metal. Did you know that
many objects around you are made
from alloys? Look at several examples
of alloys as shown in Figure 8.1.

Figure 8.1 Examples of alloys and their importance

At the end of the lesson,
pupils are able to:
8.1.1	 Describe	briefly	alloy

with examples
8.1.2 Compare the properties

of	an	alloy	with	its	pure
metal through experiment

8.1.3	 Justify	the	usage	of	alloys
based on their composition
and properties

Pewter is used to
make souvenirs.

Duralumin is used
to make the body
of an aeroplane.

Bronze is used to
make medals.

Brass is used to
make keys.

Steel is used to make
the body of a car.

Stainless steel is used
to make cutlery.

Alloy

The National Monument of Malaysia
was built using bronze.

254

THEME 4 Industrial Chemistry

LearningLearning
StandardStandard
Comparison of Properties of Alloys and Pure Metals

The strength and hardness of alloys are based on the arrangement of particles. Are alloys stronger
and harder compared to pure metals or vice versa?

Experiment 8.1

Aim: To investigate the comparison between the properties of alloys and pure metals.
Problem statement: Is an alloy more resistant to corrosion and harder than a pure metal?
Materials: Stainless steel plate, iron plate, distilled water, bronze block and copper block
Apparatus: 100 cm3 beaker, 100 cm3 measuring cylinder, sandpaper, steel ball bearing,
 1 kg weight, retort stand with clamp, meter ruler and cellophane tape

Resistance to corrosion

Hypothesis: Stainless steel is more resistant to corrosion than iron.
Variables:

(a) Manipulated : Type of plate
(b) Responding : Corrosion of plate
(c) Fixed : Size of plate and volume of distilled water

Procedure:

1. Clean the surfaces of stainless steel and iron plates by using a sandpaper. Observe the surfaces
of both plates. Record your observations.

2. Immerse both plates in a beaker containing 80 cm3 of distilled water as shown in Figure 8.2.

80 cm3 of
distilled water

Stainless steel
plate

Iron plate

Beakers

Figure 8.2

3. Leave both beakers aside for one week.
 4. After one week, remove both plates and observe the conditions of their surfaces. Record your

observations in Table 8.1.

Results:

Table 8.1

Type of plate
Condition of plate’s surface

After cleaning with sandpaper After immersing in distilled
water for one week

Stainless steel
Iron

255

CHAPTER 8Manufactured Substances in Industry
Hardness of substances

Hypothesis: Construct a suitable hypothesis for this experiment.
Variables: State the variables involved in this experiment.
Procedure:

Bronze block

Steel ball bearing

Cellophane tape

1 kg weight

Retort stand

0
1

2
3

4
5

6
7

8
9

10
11

12
13

14
15

16
17

18
19

20
21

22
23

24
25

26
27

28
29

30
cm

Figure 8.3

1. Fix a steel ball bearing on the surface of the bronze block using a cellophane tape.
 2. Hang a 1 kg weight on the retort stand at 50 cm above the surface of the bronze block, as

shown in Figure 8.3.
 3. Release the weight onto the steel ball bearing.
 4. Measure the diameter of the dent formed on the surface of the bronze block.
 5. Repeat steps 1 to 4 three times but on different surfaces of the bronze block to obtain an average

diameter of the dent formed. Record the reading in Table 8.2.
 6. Repeat steps 1 to 5 by replacing the bronze block with a copper block.

Results:

Table 8.2

Type of block
Diameter of dent (cm)

1 2 3 4 Average
Bronze

Copper

Conclusion:

Is the hypothesis acceptable? What is the conclusion of this experiment?

Discussion:

1. Why must the stainless steel plate and iron plate be cleaned with a sandpaper?
 2. Compare the rate of corrosion of the stainless steel and iron plates.
 3. Which block formed a dent with a larger diameter?
 4. State the relationship between the diameter of the dent and the hardness of the substance.

Prepare a complete report after carrying out this experiment.

256

THEME 4 Industrial Chemistry
Figure 8.4 shows the comparison between the properties of an alloy and a pure metal. The
alloying process helps to prevent the corrosion of metal and alter the properties of a pure metal to
make it harder and stronger. How did these changes happen?

Alloy Pure metal

Figure 8.4 Comparison between the properties of an alloy and a pure metal

A pure metal is made up of
one type of atom that is of the same
size and arranged in an orderly
arrangement. When force is applied,
the layers of atoms in the metal
easily slide over each other. This
causes pure metals to be ductile and
easily pulled into fine wires.

Pure metals are also malleable
and its shape can be easily changed.
There are empty spaces between the
atoms in a pure metal. When force is
applied, the layer of atoms in a metal
will slide to fill the empty spaces
and form a new structure.

An alloy is formed when
foreign atoms are mixed with the
pure metal. These foreign atoms
are different in size compared to
the atoms in the pure metal. Hence,
the orderly arrangement of atoms
in a pure metal is disrupted. This
makes it difficult for the layers of
atoms in an alloy to slide over each
other when force is applied.

Figure 8.7 Arrangement of atoms in an alloy

Figure 8.5 Pure metals are ductile

Figure 8.6 Pure metals are malleable

Force

Atom of pure metal

Force

Force

Foreign atomAtom of pure metal

257

CHAPTER 8Manufactured Substances in Industry
Competition to build a model of particle arrangement in an alloy

1. Carry out this activity in pairs.

2. Discuss with your partner and build a model to illustrate the arrangement of particles in an
alloy using balls or spheres.

3. Present your group work by explaining how the model can form an alloy with sturdy
arrangement of particles.

Justify the Uses of Alloys based on Their Composition and Properties

The uses of alloys is based on the composition and properties of the alloy produced. Alloys are
made for specific purposes. Scientists change the elemental composition to produce alloys with
different properties. For example, steel and stainless steel originate from the same pure metal,
which is iron. However, both alloys have different properties and are used for different purposes.

Table 8.3 Composition, properties and the uses of alloys

Alloy Composition Properties Uses

Duralumin •	 93% Aluminium
•	 3% Copper
•	 3% Magnesium
•	 1% Manganese

•	 Stronger than pure aluminium
•	 Low density
•	 Does not rust

•	 Body of aeroplanes
•	 Electric cables
•	 Racing bicycles

Bronze •	 90% Copper
•	 10% Tin

•	 Stronger than pure copper
•	 Does not rust
•	 Shiny

•	 Medals
•	 Monuments
•	 Trophies

Brass •	 70% Copper
•	 30% Zinc

•	 Stronger than pure copper
•	 Does not rust
•	 Shiny

•	 Musical instruments
•	 Doorknobs
•	 Keys

Steel •	 98% Iron
•	 0.2 – 2% Carbon

•	 Also known as carbon steel
•	 Stronger and harder
•	 Malleable
•	 There are three types of steel, which

are low-carbon steel, average-carbon
steel and high-carbon steel

•	 Structure of buildings
•	 Railway tracks
•	 Body of cars

Stainless
steel

•	 73% Iron
•	 18% Chromium
•	 8% Nickel
•	 1% Carbon

•	 Stronger than pure iron
•	 Resistant to corrosion

•	 Cutlery
•	 Sinks
•	 Surgical instruments

Pewter •	 95% Tin
•	 3.5% Antimony
•	 1.5% Copper

•	 Stronger than pure tin
•	 Does not rust
•	 Shiny

•	 Decorative ornaments
•	 Trophies
•	 Souvenirs

CT

* The composition percentage of metals in each alloy may vary

Activity 8.1
Century
Skills21st

258

THEME 4 Industrial Chemistry
Yourself
TestTest

8.1

1. Atoms in pure iron are arranged in an orderly manner and in layers.
(a) What is the effect of atom arrangement in pure iron on the ductility and malleability of

the metal?
(b) Iron alloy can be made by mixing some carbon into molten iron. How does the

arrangement of atoms in the iron alloy affect the hardness of the alloy?
 2. The purity of gold is measured in carats (K). 24 carat gold is pure gold without the addition

of any other metal whereas 18 K gold is a mixture comprising of 18 units by mass of gold
with 6 units by mass of other metal such as copper.
(a) What is the role of copper in 18 K gold?

(b) Calculate the composition percentage by mass in 24 g of 18 K gold.

3. Justify the following statements:

(a) Stainless steel is used to make washing machines
(b) High voltage electric cables are made from aluminium alloy
(c) 18 K gold is used to make rings

Making a poster to relate the properties and suitability of alloys in

daily life

1. Carry out the Gallery Walk activity.

2. Obtain information from various reading sources and the Internet regarding the characteristics
and properties of the following alloys and their uses in daily life.

3. Discuss with your group members and design an interesting poster.
 4. Display your group work in the class. Move with your group to see the work of other groups.
 5. Write comments on other groups̕ work on sticky notes and paste them.

Superconductors were
discovered in 1911 when
mercury that was cooled
at 4 K by Heike Kamerlingh
Onnes did not have any
electrical resistance.

Photograph 8.2 Maglev train

A superconductor is an example of an alloy used in electrical
transportation such as the Maglev train. Superconductors do not have
electrical resistance at very low temperatures. This alloy is used to make
a magnet that can levitate the train and move it at a very high speed.

Activity 8.2
CTCentury

Skills21st

259

CHAPTER 8Manufactured Substances in Industry
Basic
properties

of glass

Composition of Glass and Its Uses8.2

Rainbow Skywalk in Georgetown, Penang is a bridge made of
glass. Do you know of any other structures that are made from
glass? What about the method to make glass?

Photograph 8.3 Rainbow Skywalk

Figure 8.8 Basic properties of glass

Types of Glass

In this chapter, you will learn about four types of glass, which are fused
silica glass, soda-lime glass, borosilicate glass and lead crystal glass.

Photograph 8.4 Telescope

At the end of the lesson,
pupils are able to:
8.2.1	 Describe	briefly	with

examples	the	type	of
glass, their composition,
properties and uses

When silica is heated together with other chemicals, various types of glass with different
properties are obtained. However, all types of glass have the same basic properties.

Silica, SiO2 requires high temperature around 1800 °C to melt.
Hence, fused silica glass has a high melting point. This glass
does not expand nor contract much when there is a large
change in temperature. Fused silica glass is suitable to be used
in making telescope lens.

Fused silica glass is made from silica (silicon dioxide, SiO2)
without adding any other chemical.

Electrical
insulator Transparent

Hard but
brittle

Chemically
inert

Heat
insulator Waterproof

LearningLearning
StandardStandard

260

THEME 4 Industrial Chemistry
Activity 8.3
Making a multimedia presentation about types of glass, composition,

properties and uses

1. Carry out this activity in groups.
 2. Gather information from various reading sources or the Internet about types of glass.
 3. Interpret the data regarding the composition, properties and uses of glass.
 4. Present the information obtained to the class in the multimedia presentation.

Photograph 8.5 Glass containers

Photograph 8.6
Laboratory glassware

Photograph 8.7 Prism

Soda-lime glass is made from silica, SiO2, soda (sodium
carbonate, Na2CO3) and limestone (calcium carbonate, CaCO3).

Lead crystal glass is made from silica, SiO2, soda, Na2CO3 and
lead(II) oxide, PbO.

Borosilicate glass is made from silica, SiO2, soda, Na2CO3,
limestone, CaCO3, boron oxide, B2O3 and aluminium oxide, Al2O3.

Soda, Na2CO3 lowers the melting point of silica, SiO2. Hence,
soda glass has a low melting point, around 1000 °C. This glass
is easily moulded and used to make glass containers such as
bottles and jugs. However, this glass cannot withstand high
temperatures and can easily crack when subjected to sudden
temperature change.

Lead, Pb replaces calcium, Ca to produce glass that is softer and
denser. Lead glass is heavier and has a high refractive index. This
glass is suitable to be used in making prisms.

Many laboratory glassware such as beakers and flasks are made
from borosilicate glass because of its resistance to heat. These
glassware do not crack easily when subjected to thermal stress
because of its low expansion coefficient. Borosilicate glass can
be removed from the refrigerator and heated immediately
without cracking.

CT

261

CHAPTER 8Manufactured Substances in Industry
Yourself
TestTest

8.2

1. Silica is used to make all types of glass.
(a) State the type of glass that is made up of only silica.
(b) Soda-lime glass contains alkali metal ions. Name the ion.

2. A sample of borosilicate glass has composition of 80% silica, SiO2,15% boron oxide, B2O3
and 5% alumina, Al2O3. Calculate the mass of each component in the borosilicate glass
sample with mass of 1 kg.

3.
Aini’s mother : Aini, do not store food in lead crystal glass containers.
Aini : Why not, mother?

Based on the conversation above, explain the advantages and disadvantages of using
containers made from lead crystal glass.

Photograph 8.9 Examples of ceramic products

Aluminium oxide, Al2O3 Titanium carbide, TiC Silicon carbide, SiC

Photograph 8.8 The Great Pyramid of Giza

Composition of Ceramics and Its Uses8.3

A ceramic is a solid made up of inorganic and non-metallic substances. Ceramic is produced
through the process of shaping and hardening by using heating technique at a high temperature.
Most ceramics are made up of metal compounds, non-metal compounds or metalloid compounds.
Photograph 8.9 shows examples of ceramic products.

The Great Pyramid of Giza in Egypt is
          believed to be made from ceramic.
             What is ceramic? Is ceramic a type
                 of element or compound?

At the end of the lesson,
pupils are able to:
8.3.1	 Describe	briefly	with

examples of ceramics,
their composition,
properties and uses

8.3.2 Expain the uses of
ceramics	in	daily	life

LearningLearning
StandardStandard

262

THEME 4 Industrial Chemistry
All ceramics have the same basic properties. Do ceramics have the same properties as alloys
and glass or vice versa?

Figure 8.9 Basic properties of ceramics

Traditional ceramics are made from clay such as
kaolin, Al2O3.2SiO2.2H2O. Clay is mixed with water to
produce a soft, mouldable mixture. The mixture is then
heated at a very high temperature. Generally, traditional
ceramics are used to make bricks, pottery and crockery.

Types of Ceramics

Did you know that ceramics can be classified into two groups, that is traditional ceramics and
advanced ceramics?

Activity 8.4
Classifying ceramics into traditional ceramics and advanced ceramics

1. Carry out this activity in groups.
 2. Obtain information from various reading sources or the Internet about several examples of

ceramics and the classification of ceramics into traditional ceramics or advanced ceramics.
 3. Based on the information obtained, discuss with your group members and produce a mind map.
 4. Present your group work to the class.

Photograph 8.10  Examples of traditional
ceramic use

Pottery

Bowl

CT

Electrical
insulator

Hard and
strong

Heat
insulator

High
thermal
resistant

Break
easily

Chemically
inert

Basic
properties

of ceramics

The atoms in ceramics are bonded by
strong covalent bonds and ionic bonds. Hence,
ceramics only melt at very high temperatures,
are hard and resistant to compression. When
force is applied, the atoms in ceramics cannot
slide over each other because these atoms are
strongly bonded in indefinite arrangement. The
energy from the force will be used to break
the bonds between the atoms. Hence, ceramics
are brittle and weak towards stretching. The
electrons in ceramics cannot move freely to
conduct electricity or heat.

Brick

Century
Skills21st

263

CHAPTER 8Manufactured Substances in Industry
Advanced ceramics are made from inorganic
compounds such as oxides, carbides and nitrides.
Advanced ceramics have higher resistance to heat
and abrasion, more chemically inert and have
superconductivity properties.

Advanced ceramics such as silicon carbide are
used to make cutting discs due to its hard and strong
properties. Silicon carbide is also used to make brake
discs because it can withstand thermal shocks and has
high resistance to heat. Advanced ceramics are also used
to make tungsten carbide rings because it is hard and
resistant to abrasion. What other properties and use
of traditional ceramics and advanced ceramics that
you know?

Tungsten
carbide ring

Brake disc

Cutting disc

Activity

Photograph 8.11 Examples of advanced
ceramic use

8.5
Making a multimedia presentation about the classification, properties and

uses of ceramics

1. Carry out this activity in groups.
 2. Gather information from various reading sources or the Internet about the classification,

properties and uses of ceramics.
 3. Use Table 8.4 to organise the information that you have obtained.

Table 8.4

Ceramic
Classification of ceramic

Properties Uses
Traditional Advanced

… 3 … …

4. Present the information obtained in an interesting multimedia presentation to the class.

Ceramic Uses Application

Table 8.5 Ceramic uses

Examples
of ceramic

uses

Medicine

•	 Zirconia	ceramic	is	used	in	dental	implants.
•	 Alumina	ceramic	is	used	to	make	knee	bone.
•	 Ceramic	is	used	in	Magnetic	Resonance	Imaging	(MRI)	machines

because it has superconductivity properties.

Transportation •	 Engine	components	in	jet	planes	are	made	from	ceramics.

Energy
production

•	 Ceramic	is	used	to	make	electrical	insulators	in	high	voltage	areas
such as power stations.

CT

264

THEME 4 Industrial Chemistry
Activity 8.6
Explaining the use of ceramics in house construction based on the

properties of ceramics

1. Carry out the Three Stray One Stay activity.
 2. Watch a video clip about house construction from the Internet.
 3. Based on what you have watched:

(a) List ceramic materials used in the construction of houses
(b) Discuss the properties of ceramics involved

4. Present your discussion using a suitable mind map.
 5. Select a representative to explain the use of ceramic in the construction of houses based on

their properties. The other members move to observe and obtain information from the work
of other groups.

Most traditional houses in Malaysia
are built using wood. Wood is a natural
composite material that is strong
and sturdy. What is the meaning of
composite material? Why is wood
classified as a composite material?

Composite Materials and Its Importance8.4

Photograph 8.12
Traditional house

CT

At the end of the lesson,
pupils are able to:
8.4.1 State the meaning and

properties of composite
materials

8.4.2 Describe with examples the
uses of composite materials

8.4.3 Compare and contrast the
properties of a composite
material with its

constituent materials

Yourself
TestTest

8.3

1. Fill in the blanks:
(a) Ceramic is a non  solid element and non  compound.
(b) Give three examples of substances that make up ceramics.

2. Silicon carbide is an example of advanced ceramic that has a hard structure and
diamond-like properties. Can silicon carbide be used to make drinking glass?
Explain.

3. Kaolin is a white clay used to make white pottery. What substance must be added to produce
green coloured pottery? Explain.

LearningLearning
StandardStandard

Century
Skills21st

265

CHAPTER 8Manufactured Substances in Industry
A composite material is a material made from combining two
or more non-homogeneous substances, that is matrix substance
and strengthening substance. The matrix substance surrounds and
binds the strengthening substance together.

Figure 8.10 Example of matrix substance, strengthening substance and composite material

Reinforced concrete is produced when steel bars or
wire mesh (strengthening substance) is immersed in concrete
(matrix substance). Reinforced concrete is widely used in the
construction of bridges, dams and buildings.

Matrix substance  Strengthening substance  Composite material

Cellulose fibres

Lignin
 Lignin Cellulose fibres Wood

Building Dam

Bridge

Chemistry& Us

Teeth is a composite
material made up of
hydroxyapatite and collagen.

A materials scientist
studies the structure
and chemical properties
of natural and synthetic
substances to develop
new, enhanced materials.

Career Kiosk

Both components of a composite material have different
physical and chemical properties. When combined, the composite
material formed has better properties than the original components.

Composite Materials and Their Uses

Composite materials are widely used in the development and
advancement of technology nowadays.

266

THEME 4 Industrial Chemistry
Fibre glass is produced when plastic (matrix substance)
is strengthened with glass fibres (strengthening substance).
This composite material is used to make helmets, car bumpers
and printed circuit boards.

Optical fibre consists of three layers. The innermost layer
is the core that is made up of silica glass fibres (strengthening
substance). The core is encased in a second layer or cladding that
is made up of glass or plastic (matrix substance). The outermost
layer is made of plastic that acts as a protective jacket (matrix
substance). Optical fibres are used to transmit information and
data in the form of light. Light moves through the optical fibre
(core section) in a series of total internal reflection. The core and
cladding have different refractive indexes to enable them to carry
data in large capacity and to not be influenced by electromagnetic
disturbances. This composite material has replaced copper
wires in video cameras and connects computers in Local Area
Network (LAN).

Helmet

Printed circuit boardCar bumper

Video camera

Optical fibre Cables in computer network

Protective
jacket

Cladding
layer

Core

267

CHAPTER 8Manufactured Substances in Industry
Photochromic glass is formed when glass (matrix
substance) is combined with silver chloride, AgCl and copper(I)
chloride, CuCl (strengthening substance). When exposed to sunlight,
photochromic glass darkens. This is due to the formation of silver
atoms, Ag that prevents the passage of light. In dim light, copper(I)
chloride, CuCl in photochromic glass catalyses the reverse process so
that glass becomes transparent again.
Photochromic glass protects the user
from UV rays and is suitable for use
in car windows, building windows
and camera lenses.

Superconductors such as yttrium barium copper oxide, YBCO
ceramic is a composite material that has superconductivity properties

other than alloys. This superconductor is used to make electromagnets, that
are superconductor magnets or supermagnets. Superconductor magnets are
light and have strong magnetic force. Superconductor magnets are used in
particle accelerators and involved in Nuclear Magnetic Resonance (NMR)

machines and Magnetic Resonance Imaging (MRI) machines.

Building window

Particle accelerator
Nuclear Magnetic
Resonance (NMR)

Magnetic Resonance
Imaging (MRI)

Camera lens

Car window

Photochromic
glass

http://bit.ly/
33wWTEO

268

THEME 4 Industrial Chemistry
Figure 8.13 Comparison in properties of optical fibre with its original components

Comparison and Difference in Properties of Composite Materials and Their

Original Components

Composite materials have different properties compared to their original components. What is the
difference in the properties of a composite material and its original components?

Concrete can withstand high compression forces but will break if subjected to high stretching
forces. Combination of concrete and steel bars or wire mesh can increase the ability of the concrete
to withstand compression forces.

Figure 8.12 Comparison in properties of fibre glass with its original components

Optical fibre has high compression strength although the original component that is glass
fibre, is brittle.

Figure 8.11 Comparison in properties of reinforced concrete with its original components

Plastic matrix consists of plastic that is weak, soft and easily burned. The properties of plastic
are reinforced by adding glass fibres.

Properties
 Low compression strength
 Hard

Properties
 High stretching strength
 Low heat and electrical
conductivity

Properties
 Low stretching strength
 Low heat and electrical
conductivity

Resistant to corrosion
 Durable

Properties
 High compression
strength

Flexible

Properties
 High stretching
strength

Heat and electrical
insulator

Resistant to
corrosion

Durable

Optical fibre

Fibre glass

Plastic

Glass fibre

Properties
 High compression strength
 Flexible

Plastic

Glass fibre

+

+

Properties
 High stretching strength
 Corrodes easily

Properties
 High compression strength
 Low stretching strength
 Resistant to corrosion

Properties
 High compression
strength

High stretching
strength

Resistant to
corrosion

Reinforced
concrete

Concrete

Steel bars or
wire mesh

+

269

CHAPTER 8Manufactured Substances in Industry
Property
High electrical
resistance at room
temperature

Properties
 Transparent to
visible light

Absorbs UV rays
 Sensitive to light
intensity

Properties
 Transparent
 Does not absorb
UV rays

Not sensitive to light

Property
No electrical
resistance at very
low temperature

Properties
 Transparent
 Absorbs UV rays
 The absorption
of UV rays
depends on light
intensity

Glass is transparent and does not absorb UV rays. Silver halide salt crystals such as silver
chloride, AgCl is transparent to visible light and absorbs UV rays at the same time.

Figure 8.15 Comparison in properties of superconductor with its original components

Activity 8.7
Making a multimedia presentation about the properties, examples and

comparison between composite materials and their original components

1. Carry out this activity in groups.
 2. Gather information from various reading sources or the Internet about composite materials in

terms of:
(a) Properties
(b) Examples
(c) Comparison of properties with the original components

3. Present your group work to the class in the form of multimedia presentation.

Figure 8.14 Comparison in properties of photochromic glass with its original components

Superconductors can conduct electrical current without any resistance at very low temperature
whereas its original components cannot.

CT

Superconductor
(YBCO)

Photochromic
glass

Yttrium(III) carbonate

Barium carbonate

Copper(II) carbonate

Oxygen

+

+

+

Glass

Silver
chloride

+

270

THEME 4 Industrial Chemistry
Activity 8.8
Building a composite material

1. Carry out this activity in groups.
 2. Read and understand the following passage:

The recycling of old newspapers has saved the environment. When 1 tonne of paper is
recycled each year, 7000 gallons of water, 4200 kilowatt-hour of energy and 17 trees are
saved. Old newspapers can also be reused in the production of products such as baskets,
bag handles and paper maché. Starting from this simple effort, you have played a role in
building a safe, healthy and beautiful world.

3. Discuss with your group members and draw a composite material. This drawing must combine
at least two of the following substances:

4. Write the procedure and build the creation.
 5. Present the group work in class. The other group members can obtain information about other

groups’ work to improve on the creation.

STEM CT

Yourself
TestTest

8.4

1. Concrete is an example of composite material that has been used since ancient times.
(a) What is the meaning of composite material?
(b) Is concrete suitable to be used to build the pillars of buildings? Explain.
(c) Explain how concrete may be reinforced.

(d) State two uses of reinforced concrete.

2. Fibre glass is made by immersing glass fibre in molten plastic.
(a) Name the matrix substance and strengthening substance used to make fibre glass.
(b) Explain why fibre glass is suitable to be used to make water storage tanks.

3. Optical fibre has replaced copper wire in the transmission of information and data.
(a) Name three structures that make up an optical fibre.
(b) How does optical fibres transmit information and data?
(c) Compare the usage of optical fibres and copper wires in high definition cable

TV network.

4. Photochromic glass is a composite material which is always used to make car windows.

(a) State the main component in photochromic glass.
(b) Which component in 4(a) is sensitive to UV light?
(c) State two other uses of photochromic glass.

271

CHAPTER 8Manufactured Substances in Industry
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272

THEME 4 Industrial Chemistry
1. What new knowledge have you learned in Manufactured Substances in Industry?
 2. Which is the most interesting subtopic in Manufactured Substances in Industry? Why?
 3. Give several examples of application of Manufactured Substances in Industry in daily life.
 4. Rate your performance in Manufactured Substances in Industry on a scale of 1 to 10;
  1 being the lowest and 10 the highest. Why would you rate

yourself at that level?
 5. What can you do to improve your mastery in Manufactured

Substances in Industry?

https://bit.ly/
2BiDzPy

Achievement 8

1. The addition of coke (carbon) in the extraction process of iron is to remove oxygen from
iron ore. The iron and carbon mixture will form steel. Table 1 shows two types of steel with
different percentage of carbon.

Table 1

Steel Carbon %
Cast iron 4.0
High-carbon steel 0.8

(a) Cast iron is brittle whereas high-carbon steel is hard and strong. Based on Table 1,
calculate the percentage of carbon that must be removed from cast iron to produce
high-carbon steel.

(b) Stainless steel is produced from a mixture of chromium, nickel and carbon.
(i) State the percentage of chromium, nickel and carbon in stainless steel.
(ii) Stainless steel is suitable to be used to make high quality knife blades. Explain.

2. Lead crystal glass can be used to make spectacle lenses.
(a) What is the composition of lead crystal glass?
(b) Explain the advantages and disadvantages of using lead crystal glass to make
 spectacle lenses.

(c) Nowadays, spectacle lenses are made from polycarbonate polymer. The properties of
polycarbonate are as follows:

•	 Low	density	and	easily	moulded
•	 Absorbs	UV	rays	and	is	very	transparent
•	 High	impact	resistance

You need a pair of new spectacles. Will you choose lenses made from lead crystal glass
or polycarbonate? Explain your answer.

Self Reflection

273

CHAPTER 8Manufactured Substances in Industry
3. Traditional ceramics are made from clay such as kaolin.
(a) Name two oxide compounds found in kaolin.
(b) Give the formula of the ion that produces brown colour in clay.
(c) State two uses of traditional ceramics.

4. The various unique properties of ceramics are modified in its use in various fields. State the
property of ceramic involved in the manufacture of the following objects:

(a) Car engine

(b) Spark plug

5. Metals can conduct electricity. Ceramic materials can also be processed to conduct electricity
and be made superconductors. Figure 1 shows the change in the electrical resistance value of
two conductors against the temperature.

0 K 4 K

Non-superconductor
metal

Superconductor X

Temperature

R
es

is
ta

nc
e

Figure 1
(a) Give an example of a ceramic that shows superconductivity properties.
(b) Explain the difference in the electrical conductivity properties of the two conductors
 in Figure 1.

(c) How do scientists create a very cold condition to investigate the superconductivity
phenomena?

CornerEnrichmen

1. Silicon carbide, SiC is a hard and strong substance that melts
at 2700 °C. Silicon carbide, SiC is suitable to be used as an
abrasive. Explain why this substance is hard and has high
melting point.

Check   AnswersAnswers

https://bit.ly/
367eOnU

Figure 1

Carbon, C

Silicon, Si

274

THEME 4 Industrial Chemistry
275

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276

Element Symbol Proton
number

Relative
atomic mass

Melting
point (°C)

Boiling point
(°C)

Density
(g cm-3)

Aluminium Al 13 27 660 2350 2.70200
Silver Ag 47 108 962 2160 10.50000
Argon Ar 18 40 -189 -186 0.00170
Barium Ba 56 137 710 1640 3.59000
Beryllium Be 4 9 1285 2470 1.84800
Boron B 5 11 2030 3700 2.47000
Bromine Br 35 80 -7 59 3.11900
Iron Fe 26 56 1540 2760 7.89400
Fluorine F 9 19 -220 -188 0.00160
Phosphorus P 15 31 44 280 1.82000
Helium He 2 4 -270 -269 0.00017
Hydrogen H 1 1 -259 -252 0.00008
Iodine I 53 127 114 184 4.95000
Potassium K 19 39 63 777 0.86200
Calcium Ca 20 40 839 1490 1.55000
Carbon C 6 12 3500 4827 2.26000
Chlorine Cl 17 35.5 -101 -34 0.00300
Cobalt Co 27 59 1495 2870 8.90000
Crypton Kr 36 84 -156 -152 0.00350
Chromium Cr 24 52 1860 2600 7.19000
Copper Cu 29 64 1084 2580 8.93000
Lithium Li 3 7 180 1360 0.53400
Magnesium Mg 12 24 650 1100 1.73800
Manganese Mn 25 55 1250 2120 7.47000
Sodium Na 11 23 98 900 0.97100
Neon Ne 10 20 -248 -246 0.00080
Nickel Ni 28 59 1455 2150 8.90000
Nitrogen N 7 14 -210 -196 0.00120
Oxygen O 8 16 -219 -183 0.00130
Lead Pb 82 207 327 1760 11.35000
Rubidium Rb 37 85.5 39 705 1.53000
Caesium Cs 55 133 29 670 1.87300
Silicon Si 14 28 1410 2620 2.33000
Scandium Sc 21 45 1540 2800 2.99000
Tin Sn 50 119 232 2270 7.28000
Sulphur S 16 32 115 445 1.96000
Titanium Ti 22 48 1670 3300 4.51000
Vanadium V 23 51 1920 3400 6.09000
Xenon Xe 54 131 -122 -108 0.00550
Zinc Zn 30 65 420 913 7.14000

The data table of elements
277

Abrasion Resistance towards surface friction that occurs in a structure.

Acidic oxide Oxide compound formed from the reaction between non-metals
and oxygen.

Antiseptic Chemical substance used to kill or prevent the growth of bacteria.

Aqueous solution A solution which solvent is water.

Atom The smallest particle in an element that takes part in a reaction.

Basic oxide Oxide compound that is formed from the reaction between metals
and oxygen.

Boiling point Constant temperature at which a substance changes from liquid to
gas at a particular pressure.

Chemical equation A way of writing that describes a chemical reaction in the form of
words or chemical formula.

Chemotherapy Treatment that involves the use of certain chemicals to treat and
control certain diseases, especially cancer.

Coefficient The number in front of a chemical formula in a chemical equation.

Colouring agent Natural of synthetic colouring substance that is added to enhance
the final colour of processed food.

Crystallisation The process or forming crystals from a saturated solution.

Degree of dissociation Mole ratio of reactants that has dissociated to products in 1 litre
of solution.

Delocalised electron Electron that moves freely and is not owned by any atoms or ions.

Disinfectant Germ-killing agent used to sterilise objects such as laboratory
equipment.

Duplet electron Stable arrangement of two electrons in the valence shell.
arrangement

Electron Negatively charged subatomic particle that orbits the nucleus of
an atom.

Electronegativity The tendency of an atom to pull shared electrons towards itself in a
covalent bond.

Expansion coefficient The change in particle size to temperature changes ratio.
278

Fungicide Chemical substance to retard or destroy fungi.

Herbicide Chemical substance to retard or destroy weeds.

Lewis structure Diagram that shows the bonds between atoms in a molecule and the
electron lone pairs in a molecule.

Maglev Train transportation system that uses magnets to levitate and
propel trains.

Metalloid Element with metal and non-metal properties.

Neutron Neutral subatomic particle in the nucleus of an atom.

Octet electron Stable arrangement of eight electrons in the valence shell.
arrangement

Pesticide Poison that is used to kill pests.

Pharmaceutical Field related to medicine.

Precipitate Solid that does not dissolve in a solvent and deposited at
the bottom.

Preservative Food additive that delays or prevents the growth and reproduction
processes of microorganisms that spoil food.

Proton Positively charged subatomic particle in the nucleus of an atom.

Reactant Starting material in a chemical reaction.

Reaction pathway Refers to a reaction coordinate diagram that shows the change of
energy when a reaction occurs.

Refractive index The ratio of the speed of light in vacuum to the speed of light in a
particular medium.

Saturated solution Solution that contains maximum amount of solute and cannot
dissolve any more solute at a particular temperature.

Semiconductor Substance that has electrical insulator and conductor properties.

Solute Substance that dissolves in a solvent.

Stoichiometry Study that is related to the quantity of substance involved in a
chemical reaction.

STP Abbreviation for standard temperature and pressure, which is 0 °C
and 1 atm respectively.

Volatility The property of a liquid that rapidly changes to vapour.
279

Ameyibor, K. & Wiredu, M.B. (2006). Chemistry for Senior Secondary Schools. Oxford: Macmillan Education.

Cheng, E., Chow, J., Chow, Y.F., Kai, A., Lai, K.K. & Wong, W.H. (2010). HKDSE Chemistry – A Modern
View 1. Hong Kong: Aristo Educational Press Ltd.

Cheng, E., Chow, J., Chow, Y.F., Kai, A., Lai, K.K. & Wong, W.H. (2010). HKDSE Chemistry – A Modern
View 2. Hong Kong: Aristo Educational Press Ltd.

Department of Information. (2018). Rukun Negara. Accessed on 24th July 2019, from http://www.
penerangan.gov.my/dmdocuments/rukun_negara_2018/mobile/index.html#p=4

Department of Occupational Safety and Health. (2013). Occupational Safety and Health (Classification,
Labelling and Safety Data Sheet of Hazardous Chemicals) Regulations 2013. Accessed on 24th
July 2019, from http://www.dosh.gov.my/index.php/legislation/eregulations/regulations-under-
occupational-safety-and-health-act-1994-act-514/1125-01-occupational-safety-and-health-
classification-labelling-and-safety-data-sheet-of-hazardous-chemicals-regulations-2013/file

Gallagher, R., & Ingram, P. (2015). Complete Chemistry for Cambridge IGCSE. Oxford: Oxford University
Press.

Harwood, R., & Lodge, I. (2014). Cambridge IGCSE Chemistry Coursebook with CD-ROM. Cambridge:
Cambridge University Press.

Hayworth, R.M. & Briggs, J.G.R. (2006). All About Chemistry ‘O’ Level. Singapore: Pearson Education.

Hayworth, R.M. & Briggs, J.G.R. (2010). Chemistry Insights ‘O’ Level (2nd e.d.). Singapore: Pearson Education.

Honeysett, I., Lees, D., Macdonald, A. & Bibby, S. (2006). OCR Additional Science for GCSE. Oxford:
Heinemann Educational Publishers.

Jones, M., Harwood, R., Lodge, I., & Sang, D. (2017). Cambridge IGCSE Combined and Co-ordinated
Sciences Coursebook with CD-ROM. Cambridge: Cambridge University Press.

Lim, K.C., Yeo, P.C., Tan, S.H., Cheong, S.L., Chin, S.M., Yabi, S., Guoh, S.L. & Mohamad, K. (2012). Buku
Teks KBSM Kimia Tingkatan 5. Selangor: Pan Asia Publications Sdn. Bhd.

Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. (2011). Chemistry Practical Book KBSM Form
4. Kuala Lumpur: Abadi Ilmu Sdn. Bhd.

Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. (2011). Chemistry Textbook KBSM Form 4.
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dalam-makmal

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280

Acid basicity 137
Activation energy 243, 244,
246, 247
Alkali metal 81, 87, 88, 90, 91
Alloy 254-259, 263, 268
Anion 67, 68, 112
Atomic structure 35
Avogadro constant 50, 73

Catalyst 235, 236, 241, 246,
247
Cation 67, 68, 112
Ceramic 262-264, 268
Chemical bond 110, 126, 128
Chemical equation 69, 70, 72
Chemical formula 59, 60, 65,
67, 70
Chemical technology 6
Composite material 265-269
Covalent bond 110, 114-117,
119, 120, 126, 128, 263
Covalent compound 119, 122,
125-129

Dative bond 120
Double bond 114, 115
Double decomposition
reaction 180, 186, 187

Effective collision 243-247
Electronic arrangement 35,
82, 83, 86, 110, 112-116, 120
Electrostatic attraction force
113, 121, 125-127
Empirical formula 60, 61, 64,
65,190
Energy profile diagram 244,
248

Freezing point 26

Giant molecule 128
Glass 260, 261, 267-270
Group 80, 82, 83

Halogen 92-95
Hydrogen bond 117-119

Indicator 170, 172
Insoluble salt 179, 180, 186,
188, 190, 200, 221
Ionic bond 110, 111, 113, 116,
126, 127, 263
Ionic compound 67, 113, 122,
125-127, 129, 174, 175, 178
Isotope 37, 38, 45, 91, 243

Lewis structure 115

Matter 4, 24-26, 30, 70
Melting point 26, 85, 88, 91,
93, 101, 126-128
Metallic bond 88, 121
Metalloid 97, 99
Molar mass 52, 73
Molar volume 54, 56
Molarity 158, 159, 160, 164,
172
Mole 49, 50, 52-54
Molecular formula 60, 65

Natural abundance 37
Neutralisation 167-170, 172,
174
Noble gas 84, 85, 110
Nucleon number 32, 34, 37

Period 81-83, 96-99
Periodic Table of Elements
80-83, 101
pH 15, 16, 143-148, 152

pOH 144
Product of reaction 70, 72,
221, 226, 235, 243, 244,247,
248
Protective equipment 12
Proton number 32, 34, 35, 37,
81-83
Pure metal 255, 257, 258

Qualitative analysis 197, 199,
200, 212

Rate of reaction 221, 224-226
Reactant 221, 222, 226, 227,
230, 231, 236, 243-248
Recrystallisation 184
Relative atomic mass 37, 44-
48, 52
Relative formula mass 48
Relative molecular mass 45,
47

Scientific method 8-10
Simple molecule 127, 128
Single bond 114
Standard solution 162-166
Strength of acid and alkali
149
Superconductor 259, 268, 270

Theory of collision 243
Titration 170
Transition elements 101-104
Triple bond 114, 115

Valence electron 35, 82, 83,
91, 110, 112, 115, 116, 121
Van der Waals attraction force
119, 127, 128
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