Datasets:

vasugoel

/

K-12Corpus

like 2

Using the periodic table we can easily give the electronic configurations of any element

For example, phosphorus () is in the third period and group 15

Looking at the figure above, we see that the p-orbital is being filled

Similar trends are observed in the other periods of the periodic table

The chlorides are compounds with chlorine and the oxides are compounds with oxygen

no oxides, but fluorine does combine with oxygen in compounds called oxygen fluorides

Draw a line graph to show the relationship between atomic number (on the x-axis) and ionisation energy (y-axis)

A chemical bond is formed when atoms are held together by attractive forces

This attraction occurs when electrons are shared between atoms, or when electrons are exchanged between the atoms that are involved in the bond

The sharing or exchange of electrons takes place so that the outer energy levels of the atoms involved are filled, making the atoms are more stable

If an electron is shared, it means that it will spend its time moving in the electron orbitals around both atoms

If an electron is exchanged it means that it is transferred from one atom to another

In other words one atom gains an electron while the other loses an electron.Chemical bond A chemical bond is the physical process that causes atoms and molecules to be attracted to each other and held together in more stable chemical compounds

The type of bond that is formed depends on the elements that are involved

In this chapter, we will be looking at three types of chemical bonding: covalent, ionic and metallic bonding.You need to remember that it is the valence electrons (those in the outermost level) that are involved in bonding and that atoms will try to fill their outer energy levels so that they are more stable

The noble gases have completely full outer energy levels, so are very stable and do not react easily with other atoms.

A medium is the substance or material through which a pulse moves

The medium does not create the pulse and the medium is not the pulse

Therefore the medium does not travel with the pulse as the pulse moves through it.In each medium, the particles that make up the medium are moved temporarily from their rest position

In order for a pulse to travel, the different parts of the medium must be able to interact with each other.Medium A medium is the substance or material in which a pulse will move

The most obvious examples are waves in water, on a dam, in the ocean, or in a bucket

All waves have the same properties.Waves do not only occur in water, they occur in any kind of medium

Earthquakes release enough energy to create waves that are powerful enough to travel through the rock of the Earth

When your friend speaks to you sound waves are produced that travel through the air to your ears

A wave is simply the disturbance of a medium by moving energy but how is it different from a pulse?

Longitudinal waves A longitudinal wave is a wave where the particles in the medium move parallel to the direction of propagation of the wave

When we studied transverse waves we looked at two different motions: the motion of the particles of the medium and the motion of the wave itself

We will do the same for longitudinal waves.The question is how do we construct such a wave?A longitudinal wave is seen best in a slinky spring

Do the following investigation to find out more about longitudinal waves.From the investigation you will have noticed that the disturbance moves parallel to the direction in which the spring was pulled

The ribbon in the investigation represents one particle in the medium

The particles in the medium move in the same direction as the wave.Video: VPdkfAs in the case of transverse waves the following properties can be defined for longitudinal waves:wavelength, amplitude, period, frequency and wave speed.

A tuning fork is an instrument used by musicians to create sound waves of a specific frequency

They are often used to tune musical instruments.Sound waves coming from a tuning fork are caused by the vibrations of the tuning fork which push against the air particles in front of it

As the air particles are pushed together a compression is formed

The particles behind the compression move further apart causing a rarefaction

As the particles continue to push against each other, the sound wave travels through the air

Due to this motion of the particles, there is a constant variation in the pressure in the air

This means that in media where the particles are closer together, sound waves will travel faster.Tuning forkSound waves travel faster through liquids, like water, than through the air because water is denser than air (the particles are closer together)

Sound waves travel faster in solids than in liquids.A sound wave is a pressure wave

This means that regions of high pressure (compressions) and low pressure (rarefactions) are created as the sound source vibrates

These compressions and rarefactions arise because the source vibrates longitudinally and the longitudinal motion of air produces pressure fluctuations.

The most common example of electromagnetic (EM) radiation is visible light

Everyone is very familiar with light in everyday life, you can only see things because light bounces off them and enters your eyes

This alone makes it worthwhile to learn about it but there are also very many other applications of EM radiation

It is called electromagnetic because there are electric and magnetic fields making up the radiation

We will look at this in more detail a little later.In everyday experience, light doesn't seem to have many special properties but it does: A huge spectrum: The light we can see (visible EM radiation) is only a small part of all of the EM radiation (electromagnetic spectrum) that exists

Nature's speed limit: Nothing moves faster than the speed of light

Wave nature: All EM radiation has the ability to behave like a wave which we call wave-like behaviour

Particle nature: All EM radiation has the ability to behave like a particle which we call particle-like behaviour

No medium required: EM radiation can propagate without a medium through which to move even though they are waves

We will discuss this in the following sections and in even more detail in Grades 11 and 12.

Diagrams of compounds are very useful because they help us to picture how the atoms are arranged in the compound and they help us to see the shape of the compound

There are three types of diagrams that are commonly used: Wireframe or stick models In this model, the bonds between atoms are shown as “sticks”

Ball and stick models This is a 3-dimensional molecular model that uses “balls” to represent atoms and “sticks” to represent the bonds between them

The centres of the atoms (the balls) are connected by straight lines which represent the bonds between them

Table 12.1 shows examples of the different types of models for all the types of compounds.Covalent molecularCovalent networkIonic networkMetallic networkName of compoundglucosegraphitesilver chloridezincFormula or Stick modelBall-and-stick modelSpace-filling model Table 12.1: Different representations for compounds CanvasMol (www.alteredqualia.com/canvasmol) is a website that allows you to view several compounds

You do not need to know these compounds, this is simply to allow you to see one way of representing compounds.

The synthesis (forming) of water () from hydrogen gas () and oxygen gas () is another example of chemical change

A simplified diagram of this reaction is shown in Figure 13.3

The chemical bonds between in and between in are broken and new bonds between and (to form ) are formed

A chemical change has taken place.Video: VPbhyA mixture of hydrogen and oxygen gas is used as a fuel to get rockets into space.There are some important things to remember about chemical changes: Arrangement of particles During a chemical change, the particles themselves are changed in some way

In the example of hydrogen peroxide that was used earlier, the molecules were split up into their component atoms

The number of particles will change because each molecule breaks down into two water molecules () and one oxygen molecule ()

Energy changes The energy changes that take place during a chemical reaction are much greater than those that take place during a physical change in matter

During a chemical reaction, energy is used up in order to break bonds and then energy is released when the new product is formed

Reversibility Chemical changes are far more difficult to reverse than physical changes

When hydrogen peroxide decomposes into water and oxygen, it is almost impossible to get back to hydrogen peroxide

Mass conservation Mass is conserved during a chemical change, but the number of molecules may change

In the example of the decomposition of hydrogen peroxide, for every two molecules of hydrogen peroxide that decomposes, three molecules are formed (two water and one oxygen)

Table 13.1 highlights these concepts for the decomposition of hydrogen peroxide.Moleculestwo moleculesthree moleculesEnergy changesenergy taken in when bonds are brokenenergy given off when bonds are formedMass is conservedAtoms are conserved oxygen atoms, hydrogen atoms oxygen atoms, hydrogen atoms Table 13.1: Important concepts in chemical change Exercise 13.1See solutions For each of the following say whether a chemical or a physical change occurs

Melting candle wax.Mixing sodium chloride () and silver nitrate () to form silver chloride ().Mixing hydrochloric acid () and magnesium ribbon () to form magnesium chloride ().Dissolving salt in water.Tearing a piece of magnesium ribbon

As we have already mentioned, a number of changes can occur when elements are combined with one another

One way of representing chemical changes is through balanced chemical equations

A chemical equation describes a chemical reaction by using symbols for the elements involved

For example, if we look at the reaction between iron and sulfur to form iron sulfide , we could represent these changes in a sentence, in a word equation or using chemical symbols: Sentence: Iron reacts with sulfur to form iron sulfide

A chemical formula shows each element by its symbol and also shows how many atoms of each element are found in that compound

The number of atoms (if greater than one) is shown as a subscript.The following exercise serves as revision

Magnetism is an interaction that allows certain kinds of objects, which are called 'magnetic' objects, to exert forces on each other without physically touching

A magnetic object is surrounded by a magnetic 'field' that gets weaker as one moves further away from the object

A second object can feel a magnetic force from the first object because it feels the magnetic field of the first object

The further away the objects are the weaker the magnetic force will be.Video: VPfkkHumans have known about magnetism for many thousands of years

For example, lodestone is a magnetised form of the iron oxide mineral magnetite

It is referred to in old European and Asian historical records; from around BCE in Europe and around BCE in Asia.Magnetic objects stuck to a magnetThe root of the English word magnet is from the Greek word magnes, probably from Magnesia in Asia Minor, once an important source of lodestone.

Electrostatics is the study of electric charge which is at rest or static (not moving)

In this chapter we will look at some of the basic principles of electrostatics as well as the principle of conservation of charge.Video: VPfmg

When you measure the potential difference across (or between) the terminals of a battery that is not in a complete circuit you are measuring the emf of the battery

This is the maximum amount of work per coulomb of charge the battery can do to drive charge from one terminal, through the circuit, to the other terminal.The volt is named after the Italian physicist Alessandro Volta (1745–1827).Electrical potential difference is also called voltage.When you measure the potential difference across (or between) the terminals of a battery that is in a complete circuit you are measuring the terminal potential difference of the battery

Although this is measured in volts it is not identical to the emf

The difference will be the work done to drive charge through the battery.BatteriesOne lead of the voltmeter is connected to one end of the battery and the other lead is connected to the opposite end

The voltmeter may also be used to measure the voltage across a resistor or any other component of a circuit but must be connected in parallel.

Many reactions in chemistry and all biological reactions (reactions in living systems) take place in water

In this chapter we will look at some of these reactions in detail

Almost all the reactions that occur in aqueous solutions involve ions

We will look at three main types of reactions that occur in aqueous solutions, namely precipitation reactions, acid-base reactions and redox reactions

Before we can learn about the types of reactions, we need to first look at ions in aqueous solutions and electrical conductivity.Video: VPbls

Sometimes it is important to know exactly how many particles (eg atoms or molecules) are in a sample of a substance, or what quantity of a substance is needed for a chemical reaction to take place.The amount of substance is so important in chemistry that it is given its own name, which is the mole.Mole The mole (abbreviation “mol”) is the SI (Standard International) unit for “amount of substance”

The mole is a counting unit just like hours or days

We can easily count one second or one minute or one hour

If we want bigger units of time, we refer to days, months and years

We call this number Avogadro's number.Avogadro's number The number of particles in a mole, equal to