A Teacher’s Guide 

For Grades 6 

Through 8

Learning About 

Acid Rain
United States Environmental Protection Agency

Office of Air and Radiation

Office of Atmospheric Programs

Clean Air Markets Division (6204J)

1200 Pennsylvania Ave., NW

Washington, D.C. 20460

EPA 430-F-08-002

April 2008

1970 1970 1977

1978 1980

1980 1986 1987

1990 1993 1994

Twenty million people 

celebrate the first 

Earth Day.

The Clean Air 

Act (CAA) 

is passed.

Congress strengthens 

the CAA and includes 

requirements for SO2

pollution control at 

power plants.

The National Atmospheric Deposition Program/National 

Trends Network (NADP/NTN) begins monitoring sulfur 

and nitrogen deposition to ecosystems.

The National Acid Precipitation 

Assessment Program (NAPAP), 

mandated by Congress, begins 

study on acid rain.

Lake acidification and fish 

loss in the Adirondacks, 

Green Mountains, and Sierra 

Nevada make national news.

The United States and Canada begin 

study of cross-border acid rain 

transport. The United States is called 

upon to reduce emissions of SO2 and 

NOX, especially from coal-burning 

power plants.

The Clean Air Status 

and Trends Network 

(CASTNET) is 

established to 

monitor dry 

deposition.

Congress strengthens the CAA and 

establishes the Acid Rain Program 

using a market-based approach to 

reduce SO2 from power plants by 

more than 50 percent.

EPA publishes acid rain 

regulations, and the 

Chicago Board of Trade 

holds first auction of 

SO2 allowances.

Projected costs of compliance 

re-estimated by the 

Government Accountability 

Office and the Electric Power 

Research Institute at less than 

half of original estimates.

1970 – 1994
1995 2000

1996 2001 2002

1997 2003 2004

1998 1999 2005

Phase I of Acid Rain Program implementation 

begins. SO2 emissions fall to 5 million tons 

below 1980 levels. Acidity of rainfall in the 

eastern United States drops 10 to 25 percent.

Phase II of Acid Rain Program 

begins, regulating additional 

smaller/cleaner plants and 

requiring further reductions 

in NOx and SO2.

About 150 of the largest 

coal-fired power plants 

begin to implement Acid 

Rain Program NOx

requirements.

More than 80 

percent of affected 

companies have 

engaged in private 

allowance 

transactions.

Regulatory revisions 

enhance efficiencies of 

compliance and 

administration. Nearly 

10 million economically 

significant allowance 

transfers take place.

Allowance 

banking peaks. 

SO2 early reductions total over 

11 million tons.

Introduction of the 

On-line Allowance 

Tracking System 

begins an era of 

paperless allowance 

transfer recording.

EPA begins electronic 

audit process to 

supplement existing 

rigorous monitoring 

program.

Lakes and streams in 

the Adirondacks, Upper 

Midwest, and Northern 

Appalachian Plateau 

show signs of recovery.

Acid Rain Program sources 

emit 34 percent less SO2

and 43 percent less NOx

than in 1990, despite a 

34 percent increase in 

fuel usage.

New study estimates 2010 annual Acid Rain 

Program benefits at $122 billion and annual 

costs at $3 billion. According to the 2005 NAPAP 

report, further emission reductions are necessary to achieve broader environmental recovery. 

EPA promulgates Clean Air Rules to further 

reduce SO2, NOx, and for the first time, mercury.

1995 – 1999 2000 – 2005
4
1

Contents

PURPOSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

OBSERVATIONS ABOUT ACIDITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

DEFINING ACID RAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Air Pollution Causes Acid Rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Acid Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Dry Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Acid Rain Is A Problem That Can Travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Natural Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

EFFECTS OF ACID RAIN ON ECOSYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Forests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Acid Rain On The Forest Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Ponds, Lakes, And Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

EFFECTS OF ACID RAIN-CAUSING POLLUTANTS ON HUMANS . . . . . . . . . . . . . . . . . . . . . 12

EFFECTS OF ACID RAIN ON MAN-MADE MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . 13

WHAT IS BEING DONE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

The Acid Rain Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Alternative Ways Of Producing Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

What You Can Do To Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

To Prevent Acid Rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

To Address Other Environmental Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

EXPERIMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Measuring With pH Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Measuring With pH Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Safety In The Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Recording Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Experiment 1: Measuring pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Experiment 2: Determining The pH Of Common Substances . . . . . . . . . . . . . . . 24

Experiment 3: Making A Natural pH Indicator . . . . . . . . . . . . . . . . . . . . . . . . . 25

Experiment 4: Measuring The pH Of Natural Water . . . . . . . . . . . . . . . . . . . . . . 26

Experiment 5: Measuring Soil pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Experiment 6: Soil Buffering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Experiment 7: Observing The Influence Of Acid Rain On Plant Growth . . . . . . . . 29

Experiment 8: Looking At Acid’s Effects On Metals . . . . . . . . . . . . . . . . . . . . . . 30

Experiment 9: Observing The Influence Of Acid Rain On Marble And Limestone . 31

Experiment ANSWERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

ACTIVITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Games . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Crossword Puzzle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Word Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Game Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Participation and Completion Certificate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2

Acid rain is a complex environmental 

problem which affects the United States 

and many other countries around the 

world. The United States Environmental 

Protection Agency (EPA) was established 

in 1970 to address environmental issues, 

such as acid rain. Through its programs, 

EPA works to protect human health and 

the environment in the United States by 

developing and enforcing regulations 

and studying environmental conditions.

In addition, EPA is committed to informing the public about environmental 

topics and its efforts to solve them 

through written materials and its Web 

site (www.epa.gov). EPA frequently 

receives requests for information about 

environmental problems from school 

systems, teachers, and individuals. Acid 

rain is one of the most frequently 

requested topics. As part of EPA’s public 

outreach on acid rain, EPA first developed this guide in 1990. This revised 

guide is designed to help students 

better understand the science, cause 

and effect, and regulatory and citizen 

action that are part of understanding 

and addressing acid rain.

This book is intended for teachers of 

students in 6th-8th grade. It is written at 

a 6th grade level and the language, 

concepts, and experiments may need to 

be adapted for other grades accordingly. 

After reading the guide and doing some 

of the experiments and activities, we 

hope that you and your students will 

have a better understanding of acid rain 

and the problems it causes, as well as a 

greater interest in its resolution and in 

applied environmental science.

In addition to this teacher’s guide, EPA 

has many other publications with 

information on research, monitoring, 

regulation, and other aspects of the acid 

rain problem. If you are interested in 

learning more, resources are available at 

www.epa.gov/airmarkets. This guide, 

“Learning About Acid Rain: A Teacher’s 

Guide for Grades 6 Through 8,” is available online at www.epa.gov/acidrain

/education/teachersguide.pdf. Printed 

copies are available for free through the 

Acid Rain Hotline (202-343-9620).

Purpose
T erminology

Natural Resources All the parts of 

the Earth that are not human-made 

and which people use, like fish, 

trees, minerals, lakes, or rivers. 

Energy Resources Natural 

resources that can be used to 

make heat, electricity, or any 

other form of energy. The most 

commonly used energy resources 

are fossil fuels (coal, oil, and 

gas), but the sun, wind, and 

anything else that makes energy 

are also energy resources. 

Fossil Fuels Oil, natural gas, and 

coal. Fossil fuels were made 

in nature from ancient plants 

and animals, and today we 

burn them to make energy. 

Pollution The release of harmful 

substances into the environment.

Pollutants Chemicals or 

other substances that are 

harmful to or unwanted in the 

environment. Some examples 

of pollutants are sulfur dioxide 

(SO2), nitrogen oxides (NOx), 

ozone, and particulate matter. 

Environment The air, water, 

soil, minerals, organisms, and 

all other factors surrounding 

and affecting an organism. 

Deposition When chemicals 

like acids or bases fall to the 

Earth’s surface. Deposition can 

be wet (rain, sleet, snow, fog) 

or dry (gases, particles). 

Acid Rain Rain that has become 

acidic by contact with air pollution. 

Other forms of precipitation, 

such as snow and fog, are also 

often included in the term acid 

rain or acid wet deposition. 

Sulfur Dioxide (SO2) A naturally 

occurring gas made of sulfur 

and oxygen that is also released 

when fossil fuels are burned. 

Introduction

Humans make use of many things found 

in nature. For example, we use trees to 

build our homes and cotton to make our 

clothes. Things that are not made by 

people, but instead occur naturally, are 

called NATURAL RESOURCES. Some 

examples of natural resources are 

plants, minerals, and water. All of these 

things are important to humans because 

they provide us with the materials we 

need to make the things we use everyday. Some of the products made from 

natural resources are obvious to us, like 

the timber and stone that make buildings. Other natural resources are not as 

noticeable, like the underground water 

table where our drinking water comes 

from. Natural resources that humans use 

to generate electricity are called ENERGY 

RESOURCES. Most energy in the United 

States comes from burning FOSSIL FUELS

such as coal, oil, and natural gas. Coal, 

oil, and natural gas are called fossil fuels 

because they were formed millions of 

years ago from dead plants and animals. 

People burn fossil fuels for many 

reasons. We burn oil and coal to make 

the electricity that we need to light 

buildings and run appliances like televisions and computers. We burn gas to 

heat our homes and to power cars, 

buses, and airplanes. Many human 

activities, including the burning of fossil 

fuels, cause POLLUTION. Pollution is the 

release of harmful substances called 

pollutants into the ENVIRONMENT. 

The air pollution created when fossil 

fuels burn does not stay in the air 

forever. Instead it can travel great 

distances, and fall to the ground again 

as dust or rain. When airborne chemicals and pollutants fall to the Earth, 

or deposit, it is called DEPOSITION. 

ACID RAIN forms when clean rain comes 

into contact with pollutants in the air, 

like SULFUR DIOXIDE (SO2), CARBON 

DIOXIDE (CO2), and NITROGEN OXIDES

(NOX). Although sulfur dioxide and 

carbon dioxide occur in the air naturally, burning fossil fuels adds more of 

these chemicals to the air. When these 

pollutants are released into the air, 

they mix and react with water, oxygen, 

and other chemicals to form acid 

rain. Acid rain then falls to the Earth 

where it can damage plants, animals, 

soil, water, and building materials. 

3

When harmful substances are released into 

the air, it causes pollution.
4

Despite its name, acid rain does not 

burn and cannot directly harm people. 

However, the pollutants that cause acid 

rain, especially SO2 and NOX, can react 

with other pollutants in the air, forming 

substances like Particulate Matter and 

ground level Ozone, which can sometimes make people sick.

While the “Acid Rain Teacher’s Guide” 

focuses mainly on the issue of acid rain, 

the EMISSIONS that result from the 

burning of fossil fuels have many other 

environmental consequences in addition 

to causing acid rain. Chemicals like NOX, 

produced by the burning of fossil fuels, 

combine with other chemicals in the 

atmosphere to form ground level ozone. 

Although the planet needs an ozone

layer for protection from the sun’s 

harmful ultraviolet rays, ozone can be 

dangerous when it forms low to the 

ground because it hurts our lungs and 

sometimes makes it difficult to breathe. 

Other chemicals that are released by the 

burning of fossil fuels are GREENHOUSE 

GASES. Greenhouse gases occur naturally 

in the Earth’s atmosphere, keeping the 

planet warm enough for humans to live. 

Without greenhouse gases, the planet 

would be an average 60° F colder than it 

is today (brrr!). However, since the 

Industrial Revolution, human activity, 

such as the burning of fossil fuels, has 

increased the amount of greenhouse 

gases in the atmosphere. By increasing 

the levels of greenhouse gases, human 

activities are affecting the mix of gases 

in the atmosphere. This is causing the 

Earth’s temperature to rise. For more 

information on climate change and its 

causes and effects, check out 

www.epa.gov/climatechange.

The consequences of air pollution are 

important to understand because air 

pollution can be carried long distances 

and affect large areas. This means that 

pollution from a town hundreds of miles 

away may be affecting your community. 

Scientists, engineers, and researchers 

monitor the effects of pollution on the air, 

forests, water, and soil. They are inventing ways to reduce the amount of 

pollution that enters the environment 

and to prevent new damage in the future. 

T erminology

Carbon Dioxide (CO2) A naturally 

occurring gas made of carbon 

and oxygen. Sources of carbon 

dioxide in the atmosphere 

include animals, which exhale 

carbon dioxide, and the burning 

of fossil fuels and biomass. 

Nitrogen Oxides (NOx) A family 

of gases made up of nitrogen 

and oxygen commonly released 

by burning fossil fuels. 

Particulate Matter Tiny solid 

particles or liquid droplets 

suspended in the air.

Ozone A chemical that is made 

of three oxygen atoms joined 

together, and found in the Earth’s 

atmosphere. There are two kinds 

of ozone: good ozone, and bad 

ozone. Good ozone is found 

high in the Earth’s atmosphere, 

and prevents the sun’s harmful 

rays from reaching the Earth. 

Bad ozone is found low to the 

ground, and can be harmful to 

animals and humans because it 

damages our lungs, sometimes 

making it difficult to breathe.

Emissions The gases that 

are released when fossil 

fuels are burned. 

Ozone Layer The layer of ozone 

that shields the Earth from 

the sun’s harmful rays.

Greenhouse Gases Gases that occur 

naturally in the Earth’s atmosphere 

and trap heat to keep the planet 

warm. Some examples are carbon 

dioxide, water vapor, halogenated 

fluorocarbons, methane, 

hydrofluorocarbons, nitrous 

oxide, perfluoronated carbons, 

and ozone. Some human actions, 

like the burning of fossil fuels, 

also produce greenhouse gases. 



#OAL



0ETROLEUM



/THER%NERGY 3OURCES



.UCLEAR



.ATURAL'AS



(YDROELECTRIC

Where Our Electricity 

Comes From

Half of our electricity in the United States is 

made by coal power plants.
Observations About Acidity

5

ACIDIC and BASIC are two extremes that 

describe chemicals, just as hot and cold 

are two extremes that describe temperature. Mixing ACIDS and BASES can cancel 

out their extreme effects; much like 

mixing hot and cold water can even out 

the water temperature. A substance that 

is neither acidic nor basic is NEUTRAL. 

The pH SCALE measures the acidic or 

basic level of a substance. The pH scale 

ranges from 0 to 14. A pH of 7 is neutral, 

while a pH less than 7 is acidic and a pH 

greater than 7 is basic. 

Pure water is neutral. However, when 

chemicals are mixed with water, the 

mixture can become either acidic or 

basic. Examples of acidic substances are 

vinegar and lemon juice. Laundry 

detergents and ammonia are examples 

of basic substances. Chemicals that are 

very basic or very acidic usually change 

or alter whatever they meet. Substances 

that have this property are called 

REACTIVE. You should be careful with 

these kinds of chemicals because they 

can cause severe burns and are often 

toxic if swallowed. For example, household drain cleaners often contain lye, a 

very basic chemical that is reactive and 

could burn you.

T er m in o l ogy

Acidic Describes a substance 

with a pH less than 7.

Basic Describes a substance with 

a pH greater than 7. Another 

word for basic is alkaline.

Acid Any of a large group of 

chemicals with a pH less than 

7. Examples are battery acid, 

lemon juice, and vinegar. 

Base Any of a large group 

of chemicals with a pH 

greater than 7. Examples are 

ammonia and baking soda. 

Neutral A substance that is 

neither an acid nor a base 

and has a pH of 7. Neutral 

substances can be created by 

combining acids and bases. 

pH Scale The range of units that 

indicate whether a substance 

is acidic, basic, or neutral. The 

pH scale ranges from 0 to 14.

Reactive Having the tendency 

to chemically combine with 

something else and change its 

form. For example, a strong acid is 

highly reactive with a strong base. 

Try These 

Experiments!

Experiment 1

Measuring pH

Experiment 2

p.23

Determining the pH of 

Common Substances

Experiment 3

p.24

Making a Natural 

pH Indicator

p.25

!CID2AIN

!DULT&ISH$IE

&ISH2EPRODUCTION!FFECTED

.ORMAL2ANGEOF0RECIPITATION

.ORMAL2ANGEOF3TREAM7ATER































,YE

)NCREASINGLY

!CIDIC

.EUTRAL

)NCREASINGLY

"ASIC

.EUTRAL

#OLA

#OFFEE

7ATER

3OAP

"ATTERY!CID

,EMON*UICE

6INEGAR

-ILK

"AKING3ODA

3EA7ATER

!MMONIA

The pH Scale
6

Defining Acid Rain

Acid rain is rain that is more acidic than 

it should be. Acid rain is a complicated 

problem affecting soil and water chemistry, as well as the life cycles of plants 

and animals on land and in the water. In 

addition, weather conditions contribute 

to air pollution and cause acid rain to 

spread vast distances. 

Air Pollution Causes 

Acid Rain 

Scientists have discovered that air 

pollution from the burning of fossil fuels 

is the major cause of acid rain. Power 

plants and factories burn coal, oil, and 

natural gas to produce the electricity we 

need to do all kinds of things, like light 

our homes. Cars, trucks, and airplanes 

also run on gasoline, a fossil fuel. 

When we burn things, they do not 

disappear. For example, when you burn 

a log in a campfire, ash is left. But what 

happened to the rest of the log? Water 

from the log becomes vapor and enters 

the air. Burning wood also releases 

chemicals and particles into the air. The 

same thing happens when we burn 

fossil fuels. Burning fossil fuels sends 

smoke and fumes into the ATMOSPHERE, 

or the air above the Earth. In the air, 

these pollutants combine with moisture 

to form acid rain. The main chemicals in 

air pollution that create acid rain are 

sulfur dioxide (SO2) and nitrogen oxides 

(NOX). Acid rain usually forms high in the 

clouds where SO2 and NOX react with 

water and oxygen. This forms SULFURIC 

ACID and NITRIC ACID in the atmosphere. 

Sunlight increases the speed of these 

reactions, and therefore the amount of 

acid in the atmosphere. Rainwater, 

snow, fog, and other forms of 

PRECIPITATION then mix with the sulfuric 

and nitric acids in the air and fall to 

Earth as acid rain. 

Acid Precipitation 

Water moves through the air, streams, 

lakes, oceans, and every living plant and 

animal in the HYDROLOGIC CYCLE, shown 

in the image to the left. In that cycle, 

water evaporates from the land and sea 

and becomes a gas in the atmosphere. 

Water in the atmosphere then 

CONDENSES, or becomes liquid again, 

Precipitation as

Rain, Snow, Hail, Fog

Runoff

Condensation

Evaporation from

Lakes, Rivers, Oceans

Hydrologic Cycle

T erminology

Atmosphere The air or gases 

that surround a planetary 

body such as the Earth. 

Sulfuric Acid An acid that can be 

produced in the atmosphere from 

sulfur dioxide, a pollutant that 

results from burning fossil fuels. 

Nitric Acid An acid that can be 

produced from nitrogen oxide, 

a pollutant that results from 

the burning of fossil fuels. 

Precipitation Water falling to 

the Earth. Mist, sleet, rain, hail, 

fog, and snow are the most 

common kinds of precipitation. 

Hydrologic Cycle The movement of 

water from the atmosphere to the 

surface of the land, soil, and plants 

and back again to the atmosphere. 
7

T erminology

Evaporate To change 

from liquid into gas.

Condense To change from gas 

or vapor to liquid form. 

Dry Deposition The falling of 

small particles and gases to the 

Earth without rain or snow. 

Runoff Water that flows off 

land into lakes and streams.

Acid Deposition Acidic material 

that falls from the atmosphere 

to the Earth in either wet 

(rain, sleet, snow, fog) or dry 

(gases, particles) forms. and forms clouds. Clouds release the 

water back to the Earth as rain, sleet, 

hail, snow, or fog. When water droplets 

form and fall to the Earth they pick up 

particles like the dust and chemicals 

that float in the air. Even clean, unpolluted air contains particles such as dust 

or pollen. Clean air also contains naturally occurring gases such as carbon 

dioxide (CO2). The interaction between 

the water droplets and the CO2 in the 

atmosphere gives rain a pH of 5.6, 

making even clean rain slightly acidic. 

However, when rain contains pollutants, 

especially SO2 and NOX, the rainwater can 

become very acidic. 

Dry Deposition 

Acid rain does not account for all of 

the acidity that falls back to Earth from 

pollutants. About half of the acidity in 

the atmosphere is deposited onto 

buildings, cars, homes, and trees—

anything!—as particles and gases. This 

process is called DRY DEPOSITION. In 

some instances, these gases and 

particles can damage or alter the things 

on which they settle. Dry deposition 

(gases and particles) is sometimes 

washed from trees and other surfaces 

by rainstorms. When that happens, the 

RUNOFF water contains acid from acid 

rain and dry deposition, making the 

combination more acidic than the falling 

rain alone. The combination of acid rain 

(wet deposition) plus dry deposition is 

called acid deposition. 

Acid Rain Is A 

Problem That 

Can Travel 

The chemical reactions that cause acid 

rain can take several hours to several 

days to occur. Years ago, when smokestacks were only a few stories high, 

pollution from smokestacks usually 

stayed near the ground and settled on 

the land nearby. This caused unhealthy 

conditions for people, plants, and 

animals near those smokestacks. To 

reduce this pollution, the government 

Try This 

Experiment!

Experiment 4

Measuring the pH 

Of Natural Water p.26

Dry deposition can be washed 

away from surfaces such as 

buildings and cars during 

rainstorms.

Tall smokestacks send pollution high into the air. The longer the pollution is in the air, the 

greater the chances that the pollutants will form acid rain.
8

passed laws for the construction of very 

tall smokestacks. At that time, people 

thought that if the pollution were sent 

high into the air it would no longer be a 

problem. Scientists now know that this 

is incorrect. In fact, sending pollution 

high into the sky increases the time that 

the pollution stays in the air. The longer 

the pollution is in the air, the greater the 

chances that the pollutants will form 

acid rain. In addition, the wind can carry 

these pollutants for hundreds of miles 

before they become joined with water 

droplets to form acid rain. For that 

reason, acid rain, or wet deposition, can 

be a problem in areas far from sources 

of pollution. Dry deposition is usually 

greater near the cities and industrial 

areas where the pollutants are released. 

Natural Acids 

There are also natural sources of acids 

such as volcanoes, geysers, and hot 

springs. Nature has developed ways of 

recycling these acids by absorbing and 

breaking them down. These natural 

acids contribute to only a small portion 

of the acidic rainfall in the world today. 

In small amounts, these acids actually 

help dissolve nutrients and minerals 

from the soil so that trees and other 

plants can use them for food. 

Unfortunately, the large amounts of 

acids produced by human activities 

overload this natural acidity and throw 

ecosystems off balance.

Formation of Acid Rain

A geyser, like the one shown 

here in Yellowstone National 

Park, is also a natural source 

of acid.

Volcanoes are a natural 

source of acid.
Effects Of Acid Rain On Ecosystems

T erminology

Ecosystem All the living and 

nonliving things in an area, as well 

as the interactions between them.

Ecology The study of ecosystems. 

Someone who studies ecology 

is called an ecologist. 

Primary Producers Organisms 

that use photosynthesis to 

produce their own food. All 

plants are primary producers. 

Primary producers are the 

base of the food chain because 

they feed everything else. 

Photosynthesis The process that 

plants use to convert sunlight 

to energy to live and grow. 

Habitat The place where a plant 

or animal lives and grows, such 

as a forest, lake, or stream. 

Nutrient Deficiency When a living 

thing lacks the vitamins and 

minerals it needs to survive.

Acid rain and the air pollution that 

causes it can severely damage 

ECOSYSTEMS. An ecosystem is all the 

living and nonliving things in an area, as 

well as the interactions between them. 

Ecosystems come in all sizes. An entire 

forest is an ecosystem, but so is a single 

tree. Some scientists even consider the 

entire Earth an ecosystem. The study of 

ecosystems is called ECOLOGY. Ecologists 

study things like predator-prey relationships, how nutrients are taken from the 

soil into trees, or the kinds of bacteria 

found in a pond. Every ecosystem is 

very interconnected, and the organisms 

that live there rely heavily on each 

other. For example, ecosystems have 

food webs, where species depend on 

one another for food. If any one animal 

is affected, so are several others. This is 

how acid rain can affect entire ecosystems. Acid rain may only damage a few 

organisms in an ecosystem, but everything else is indirectly affected. The 

damage acid rain causes can also take 

years, or even decades to reverse. 

Forests

Acid rain causes significant damage to 

forests. It directly affects trees and other 

plants which are important to the 

ecosystem as a whole because they are 

PRIMARY PRODUCERS. Primary producers 

are organisms that produce their own 

food through PHOTOSYNTHESIS, a series 

of chemical reactions that convert water 

into sugar using light from the sun to 

provide energy. Plants and some microscopic animals have this ability. Plants 

are important to ecosystems because 

they feed everything else, and provide 

important HABITAT for other animals. If 

trees and plants are damaged by acid 

rain, the effects are felt throughout the 

entire ecosystem. 

Acid rain causes trees in forests to grow 

more slowly, and in some sensitive 

species it can even make the leaves or 

needles turn brown and fall off. Red 

Spruce and Sugar Maple, two species of 

trees found mainly in the East and in 

New England, are very susceptible to 

acid rain damage. Acid rain damages 

trees by dissolving the calcium in the 

soil and in the leaves of trees. This hurts 

the tree, because calcium is a mineral 

that trees need to grow. Once the 

calcium is dissolved, the rain washes it 

away so the trees and other plants 

cannot use it to grow. Acid rain washes 

other minerals and nutrients from the 

soil in a similar fashion, causing 

Nutrient Deficiency. This is why acid 

rain can cause trees to grow more slowly. 

9

Sugar Maple leaves turn brilliant shades of red, orange, and yellow in the fall. 

People from all over the United States and the world travel to New England to see 

colorful autumn leaves like those of the Sugar Maple.
10

Nutrient deficiency causes other problems for trees and plants. The lack of 

nutrients weakens the trees, and makes 

them more sensitive to the cold. A 

well-nourished tree in healthy soil will 

survive even a very cold winter with 

little difficulty, but a tree already weakened by a mineral deficiency can die 

during a cold winter. The weakened 

trees and plants are also more sensitive 

to insects and disease. 

At the same time, acid rain causes 

the release of substances such as 

aluminum from the soil. Aluminum can 

be very harmful to trees and plants. 

Once released into soil, aluminum can 

end up in streams, rivers, and lakes, 

where it can harm or even kill fish. Less 

aluminum is released when the rainfall 

is cleaner.

The pollution that causes acid rain also 

causes HAZE by scattering light back 

towards the sky. Haze reduces the 

amount of light available for plants to 

use in photosynthesis. Since photosynthesis is the base of the food chain, acid 

rain can cause problems with the movement of nutrients to other organisms in 

ecosystems that are already impacted. 

Further reducing the amount of photosynthesis are acid fogs. Fog can often be 

more acidic than rainfall. When leaves are 

frequently bathed in acid fog, their 

protective waxy coating can wear away. 

The loss of this coating damages the 

leaves and creates brown spots. The 

leaves are then unable to use photosynthesis to turn the energy in sunlight into 

food for growth. When leaves are 

damaged, they cannot produce enough 

food energy for the tree to remain healthy. 

Acid Rain On The 

Forest Floor

A spring shower in the forest washes 

leaves and the rain falls through the 

trees to the forest floor below. Some of 

the water soaks into the soil. Some 

trickles over the ground and runs into a 

stream, river, or lake. Soil sometimes 

contains substances, like limestone, that 

buffer acids or bases. Some salts in soil 

may also act as buffers. The soil may 

NEUTRALIZE, or make less acidic, the acid 

rainwater. This ability of the soil to resist 

pH change is called BUFFERING CAPACITY. 

A BUFFER resists changes in pH. Without 

buffering capacity, soil pH would change 

rapidly. Midwestern states like Nebraska 

and Indiana have soils that are well 

buffered. Places in the mountainous 

northeast, like New York’s Adirondack 

Mountains, have soils that are less able 

to buffer acids. Other soils, like those in 

Try These 

Experiments!

Experiment 5

Measuring Soil pH p.27

Experiment 6

Soil Buffering p.28

Experiment 7

Observing the 

Influence of Acid 

Rain on Plant Growth p.29

T erminology

Aluminum A silvery-white 

metal; it is the most abundant 

metal in the Earth’s crust.

Haze When particles of dust, 

pollen, or pollution make the air 

less clear, and limit visibility.

Neutralize To combine acids 

and bases to make a neutral 

substance or solution. For 

example, acidic water can be 

neutralized by adding a base. 

Buffering Capacity The ability of a 

substance to resist changes in pH 

when acids or bases are added.

Buffer A substance, such as soil, 

bedrock, or water, capable of 

neutralizing either acids or bases. 

Rain falls through the trees to the forest floor 

and runs into streams, rivers, and lakes.
the Southern Appalachian Region, hold 

acids from acid rain, making them more 

susceptible to damage from acid rain. 

Since there are many natural sources of 

acids in forest soils, soils in forest areas 

are especially sensitive to effects from 

acid rain. 

Ponds, Lakes, 

And Streams

The effects of acid rain are most clearly 

seen in AQUATIC environments such as 

streams, lakes, and marshes. Acid rain 

flows to streams, lakes, and marshes 

after falling on forests, fields, buildings, 

and roads. Acid rain also falls directly on 

aquatic habitats.

Most lakes and streams have a pH 

between 6 and 8, because the buffering 

capacity of soil usually neutralizes 

slightly acidic, clean rain. Lakes and 

streams become acidic (pH value goes 

down) when the rainwater itself is so 

acidic that the surrounding soil cannot 

buffer the rain enough to neutralize it. 

For this reason, some lakes in areas 

where soil does not have a lot of 

buffering capacity are naturally acidic 

even without acid rain. In areas like the 

northeastern United States where soil 

buffering is poor, acid rain has made 

already slightly acidic lakes very acidic, 

with some lakes having a pH value of 

less than 5. As lakes and streams 

become more acidic, the numbers and 

types of fish and other aquatic plants 

and animals that live in these waters 

decrease. Some types of plants and 

animals are able to tolerate acidic 

waters. Others, however, are acid-sensitive and will leave or die as the pH 

declines. Some acidic lakes have no fish, 

because at pH 5 most fish eggs cannot 

hatch. At lower pH levels, adult fish can 

die. Substances like aluminum that wash 

into the water from the soil can also 

harm and kill fish.

11

pH Tolerance Chart on Aquatic Life

Some animals can survive 

in water that is moderately 

acidic, while other animals 

can only live in water that is 

near neutral. An animal that 

can survive in moderately 

acidic water is said to have a 

high tolerance for acidity. The 

chart to the left shows the pH 

tolerance of various animals. 

Where the boxes are gray, 

the animals can survive, but 

where the boxes are black, the 

animals can no longer tolerate 

the acidity and die. From the 

chart, you can see that frogs 

have a high tolerance for 

acidity, while clams and snails 

have a low tolerance.

pH 6.5 pH 6.0 pH 5.5 pH 5.0 pH 4.5 pH 4.0

Trout

Bass

Perch

Frogs

Salamanders

Clams

Crayfish

Snails

Mayfly

T erminology

Aquatic Relating to water. 

Snails have a very low pH 

tolerance of 6.0.
12

Effects Of Acid Rain-Causing 

Pollutants On Humans

T erminology

Respiratory Illness Diseases 

affecting the organs we use to 

breathe. Asthma, bronchitis, 

and pneumonia are examples 

of respiratory illnesses.

Respiratory System The organs 

in our body involved with 

the process of breathing.

Acid rain looks, feels, and tastes just 

like clean rain. Walking in acid rain, or 

even swimming in an acid lake, is no 

more dangerous for humans than 

walking or swimming in clean water. 

However, breathing air that contains the 

pollutants that cause acid rain can 

damage human health. Sulfur dioxide 

(SO2), nitrogen oxides (NOx), particulate 

matter, and ozone all irritate or even 

damage our lungs. These effects are 

mostly seen in people whose lungs have 

already been weakened by respiratory

illness, but even healthy people can 

sometimes have pain or difficulty 

breathing because of air pollution.

Ozone is a dangerous pollutant that is 

caused by air pollution, especially in the 

summer. Exposure to high levels of 

ozone have been linked to a number of 

health problems. Ozone can make 

respiratory illnesses, such as asthma, 

emphysema, and bronchitis worse. 

Ozone can also reduce the respiratory

system’s ability to fight off bacterial 

infections. Even healthy people can have 

symptoms related to ozone exposure, 

including coughing, pain with deep 

breathing, chest tightness, and shortness of breath. Over time, ozone can 

cause permanent damage to the lungs 

or even death. Small particles called 

particulate matter are made up of the 

same pollutants that cause acid rain. 

Particulate matter also damages the 

lungs. The tiny particles of dust that 

make up particulate matter can bypass 

the body’s natural defenses and become 

lodged deep in the lungs, where it can 

cause irritation and damage the lungs.

SO2 and NOX, the pollutants that cause 

acid rain, can also reduce visibility, 

limiting how far into the distance we can 

see. These pollutants form small particles in the atmosphere. These particles 

reduce visibility by scattering light. 

Reduced visibility is most noticeable in 

places like National Parks, where people 

go to see some of the nation’s most 

beautiful landscapes. 

Air pollution, shown here 

in New York City, can cause 

health problems.

These are photos from the Great Smoky Mountains National Park in Tennessee and 

North Carolina. The photo on the left, taken January 21, 1986, shows what the park 

looks like on a clear day, or a day where there is little pollution present to reduce 

visibility. The photo on the right, taken August 5, 1986, shows the same view on a 

hazy day, when the air is filled with aerosols. 
Effects Of Acid Rain 

On Man-Made Materials

13

Acid rain eats away at stone, metal, 

paint—almost any material exposed to 

the weather for a long period of time. 

Human-made materials gradually 

deteriorate even when exposed to 

unpolluted rain, but acid rain speeds up 

the process. Acid rain can rust metals 

and cause marble statues carved long 

ago to lose their features. This happens 

because marble is made of a compound 

called calcium carbonate, which can be 

dissolved by acids. Calcium carbonate 

is also found in limestone. Many buildings and monuments are made of 

marble and limestone and are damaged 

by acid rain. Repairing acid rain damage 

to buildings and monuments can cost 

billions of dollars. Historical monuments 

and buildings, such as the Lincoln 

Memorial in Washington, D.C., can 

never be replaced. 

Try These 

Experiments!

Experiment 8

Looking at Acid’s

Effects on Metals 

Experiment 9

p.30

Observing the Influence

Of Acid Rain on Marble

And Limestone 

p.31

How Acid Rain Affects 

Stonework

How Acid Rain Affects Metal

The picture on the top was taken 

in 1908. The picture on the 

bottom was taken in 1968.

The Lincoln Memorial in Washington, D.C.
14

EPA has been working with Congress and 

other federal government agencies; 

state, local, and tribal governments; 

scientists; and citizens to solve the acid 

rain problem for over 15 years. 

The Acid Rain 

Program

The Acid Rain Program was established 

by Congress as part of the 1990 Clean Air 

Act Amendments. It requires the electric 

power industry to lower emissions of 

sulfur dioxide (SO2) and nitrogen oxides 

(NOx), the pollutants that cause acid rain. 

By the year 2010, power plants must 

reduce emissions of these pollutants by 

about 50 percent from levels in 1980. 

Today, power plants emit 35 percent less 

SO2 and 46 percent less NOx than they did 

in 1990. 

The Acid Rain Program is so successful 

because it uses a CAP AND TRADE

program to reduce emissions. A cap and 

trade program is a policy that controls 

large amounts of emissions from a 

group of sources. The approach first sets 

an overall cap, or maximum amount of 

emissions allowed, for all pollution 

sources under the program. The cap is 

T erminology chosen in order to meet an 

Cap and Trade An environmental 

policy tool that controls large 

amounts of emissions from a 

group of sources. Cap and trade 

programs set a cap, or limit, on 

emissions. Then allowances for 

emissions are traded between 

sources, so that economic market 

forces allow large emissions 

reductions to be cost-effective. 

Cap A national limit that is placed 

on the amount of a pollutant 

that can be emitted. The cap 

is very important because it 

makes sure that emissions of 

a pollutant are reduced.

What Is Being Done

Initial Emissions

Total = 30 tons

Allowable Limit (Cap)

Cap Total = 15 tons

Plant A

Reduction: 5 tons

Plant B

Reduction: 7 tons

Plant C

Reduction: 3 tons

2 Allowances

3 tons 5 tons

7 tons

10 tons 10 tons 10 tons

All three plants were required to reduce their emissions from 10 tons to 5 tons each. Plant A 

reduced its emissions by 5 tons to meet the cap and be in compliance. Plant B reduced its 

emissions to 3 tons, 2 tons more than were required. Plant C only reduced its emissions to 

7 tons. This is not enough to cover its allowances and be in compliance. In a cap and trade 

program, Plant B can sell its two extra allowances to Plant C. Plant C can then use the two 

allowances it bought to cover its emissions and stay under its cap.

Notice that even though a trade took place, overall emissions for Plants A, B, and C are within 

the cap (5 + 3 + 7 = 15). Total emissions in this cap and trade system are half of what they 

used to be (30 tons vs. 15 tons).

The Rockport Power Plant in 

Rockport, Indiana, burns coal 

to produce electricity.

Cap and Trade
environmental goal. In this case the cap 

is the maximum level of SO2 and NOx

emissions that all power plants 

combined can emit. Allowances, or 

permits to pollute a specific amount, are 

then given to power plants. It is up to 

the individual power plants to decide 

how they want to lower their emissions, 

but the total amount of emissions from 

all power plants across the country must 

be less than the cap. If one source 

reduces their emissions far below the 

amount assigned to them, they are 

allowed to sell their leftover emission 

allowances to another power plant that 

did not reduce their emissions enough. 

The option of selling extra emission 

allowances to make money is an incentive for the power plants to reduce their 

emissions even more than required. 

Companies that do not reduce their 

emissions enough and emit more 

pollution than they have allowances for, 

must buy allowances to cover their 

emissions or face heavy fines and other 

strict penalties. This rarely happens in 

the Acid Rain Program because the strict 

penalties discourage power plants from 

not having enough allowances. In fact, 

in 2006, the Acid Rain Program had 

100 percent compliance from sources 

of emissions.

Power plants can reduce the amount of 

pollution they produce in several ways. 

Some plants choose to wash the sulfur 

out of coal before it is burned. There are 

also different kinds of coal and some 

have less sulfur and nitrogen in them. 

Pollutants can also be removed from the 

smoke as it travels through the smokestack. A device called a SCRUBBER

removes sulfur from the smoke by 

spraying a mixture of water and 

powdered limestone into the smokestack. This mixture traps the sulfur 

before it can escape into the air above. 

There are also several other ways to 

decrease the pollution coming from 

power plants and scientists and engineers are always discovering new ones. 

Source: CASTNET Source: CASTNET

T erminology

Allowance The permission, given 

by the government, to emit a 

certain amount of sulfur dioxide 

(SO2) or nitrogen oxide (NOx).

Scrubber A device that removes 

air pollution, mainly sulfur 

dioxide, from smokestacks. 

These maps show how the Acid Rain Program has reduced the amount of wet acid deposition (acid rain) in the United States. 

In these maps, the dark areas represent places with high amounts of acid rain. Notice how the areas with lots of acid rain in 

1989–1991 have shrunk since the Acid Rain Program started.

Wet Acid Deposition, 1989-1991 Wet Acid Deposition, 2003-2005

15
16

Cap and trade is most effective when the 

environmental or public health issue 

occurs over a large area, when there are 

many sources of pollution which contribute to the problem, when emissions can 

be monitored, and when there is variety 

in the amount of money that sources 

must pay to reduce their emissions. 

A mandatory cap on emissions is critical 

to protect public health and the environment. The Acid Rain Program and the 

NOX Budget Trading Program have been 

very effective in reducing emissions of 

SO2 and NOX. Though long-term environmental monitoring has proven that these 

programs are working, studies have 

shown that more reductions in emissions are necessary to protect human 

health and the environment. In 2009, a 

new program called the Clean Air 

Interstate Rule (CAIR) will begin. This 

program will lower power plant 

emissions of SO2 and NOX in the eastern 

United States even further than the Acid 

Rain Program.

To learn more about cap and trade, go to 

the Clean Air Markets cap and trade Web 

site at www.epa.gov/airmarkets/cap-trade/. 

If you want to know more about the other 

cap and trade programs, like the NOx

Budget Trading program or CAIR, go to the 

Clean Air Markets program Web site at 

www.epa.gov/airmarkets. 

Monitoring

How does EPA know its programs are 

working? Experts from EPA, states, 

universities, and other agencies have set 

up air quality and deposition monitoring 

stations across the country. These 

monitoring stations contain equipment 

that constantly collects air quality data 

and samples. These devices measure 

many things, including the amount of 

pollution in the air, the pH of rain, the 

amount of rainfall, and the surrounding 

temperature. There are several networks 

made up of many stations taking 

samples in different areas. The Clean Air 

Status and Trends Network (CASTNET) 

takes samples from mostly rural areas 

around the United States. CASTNET 

measures dry deposition and collects 

atmospheric data. The National 

Atmospheric Deposition Program (NADP) 

has sites around the United States and 

focuses on precipitation and 

meteorological monitoring. By using 

this information, EPA is able to track the 

success of the Acid Rain Program and 

other cap and trade programs by linking 

CASTNET Monitoring Stations

A CASTNET 

Monitoring Site

CASTNET now has over 80 monitoring stations across the United States.

T erminology

Atmospheric Relating to the 

atmosphere, or the air above 

the Earth. 

Meteorological Pertaining to 

the weather.
T erminology

Hydroelectric Power Energy that 

is generated by dams, which 

use water to turn turbines 

and generate electricity. 

Wind Power Energy that is 

generated when the wind 

turns the sails of a windmill, 

which are attached to turbines 

that generate electricity. 

Nuclear Power Energy that 

comes from breaking apart the 

center (nucleus) of an atom. 

Solar Power Electricity that 

is generated by harnessing 

the energy of the sun. Solar 

panels are often used to 

convert sunlight into energy. 

Fuel Cells Similar to batteries, 

fuel cells store energy that can be 

used to power all sorts of things. 

Unlike a battery though, fuel cells 

do not “run out” and do not need 

to be recharged or replaced.

Turbine A motor activated by water, 

steam, or air to produce energy. 

reductions in emissions to improvements 

in air quality. You can see these monitoring stations and the information they 

collect online at http://camddataandmaps

.epa.gov/gdm/.

EPA also requires power plants to use 

Continuous Emissions Monitoring 

Systems (CEMS) to keep track of the 

amount of pollution they release into 

the air. A CEMS is a monitoring device 

that each unit must place on their 

smokestack. These monitors take 

samples of the air traveling through the 

smokestack, and measure the amount of 

pollutants traveling through it. Then, the 

monitor sends the recordings to EPA. 

CEMS allows EPA to keep track of 

emissions to make sure that the power 

companies are following the laws to 

reduce pollution. 

Alternative Ways Of 

Producing Energy 

There are other sources of energy 

besides fossil fuels. These include 

hydroelectric power, wind power, 

NUCLEAR POWER, solar power, and fuel

cells. Hydroelectric dams use the power 

of water to turn TURBINES and make 

electricity. Windmills work the same way 

but instead, use wind to turn the 

turbines. People have been using wind 

and water power for centuries. Nuclear 

power plants collect the energy released 

by splitting tiny atoms apart inside 

nuclear reactors. Although nuclear power 

plants generate dangerous waste that 

must be disposed of carefully, a small 

amount of nuclear fuel can make a very 

large amount of electricity. Some people 

also use solar power, or power from the 

sun, to make electricity. Some houses 

use solar power to heat water for 

showers, and even some traffic signs 

run off of solar panels. Fuel cells are 

similar to batteries, except that fuel cells 

run on oxygen and hydrogen. They use 

chemical reactions to generate electricity, and produce water as a waste. 

All sources of energy have benefits and 

limitations, including the cost of producing the energy. All of these factors must 

be weighed when deciding which energy 

source to use. 

17

Solar Power: Solar panels 

produce electricity.

Wind Power: Windmills produce electricity.
18

What You Can Do To Help

Taking public transportation can help reduce acid rain-causing emissions.

All environmental problems, including 

acid rain, are caused or impacted by the 

combined actions of individual people. 

This is why individuals can play a big 

part in solving these problems. While you 

cannot run a nationwide cap and trade 

program from your classroom, there are 

many things you can do to help reduce 

pollution and protect the environment. 

To Prevent Acid Rain 

1. Conserve electricity by turning off 

lights, appliances, and computers when 

no one is using them.

2. Join ENERGY STAR®’s “Change a Light, 

Change the World” program and pledge 

to use energy-efficient light bulbs in 

your home. This will reduce the amount 

of energy you use, and in turn reduce 

the amount of emissions produced by 

power plants. You can also lower your 

energy consumption by using other 

Energy Star® products and appliances, 

including TVs, computers, refrigerators, 

washing machines, air conditioners,

furnaces, etc. For more information, 

see EPA’s Energy Star® Web site 

www.energystar.gov.

3. You can greatly reduce acid rain-causing emissions (especially NOX emissions) 

by changing your transportation habits. 

Try to reduce the amount of time you 

spend in the car by walking, biking, or 

taking public transportation. When you 

drive, plan trips ahead of time to 

minimize miles traveled, drive the most 

fuel-efficient car you can, and carpool 

whenever possible. The EPA publishes a 

green vehicle guide at www.epa.gov

/greenvehicles/. 

4. Shrink your “carbon footprint” and 

reduce greenhouse gas emissions by 

turning the thermostat down a little bit in 

winter, or up a little bit in the summer. 

New technologies can also greatly 

increase the efficiency of your heating 

and air conditioning and other 

appliances. Look for the Energy Star®

Label. EPA provides information about 

some of these technologies and other 

ways to reduce greenhouse gas emissions 

at www.epa.gov/climatechange/wycd.
19

To Address Other 

Environmental 

Problems

1. Volunteer to help clean up trash and 

litter in local streams and rivers, or help 

restore wetlands. By cleaning up trash, 

you help protect ecosystems that are 

important habitats to wildlife. Information 

about wetland restoration efforts in your 

area can be found in the restoration 

project directory at www.epa.gov/owow

/wetlands/restore/. 

2. Recycle everything you can at home 

and if your school does not already have 

a recycling program, start one! This 

reduces the amount of waste that you 

produce, and keeps recyclable materials 

out of landfills. Also, try to buy products 

with less packaging, or products with 

recyclable packaging. More information 

about recycling and waste reduction 

programs can be found at EPA’s solid 

waste education Web site, www.epa.gov

/epaoswer/education.

3. Many areas of the United States, 

especially the Southwest, have problems 

with water availability. Conserving water 

helps ecosystems and the people and 

animals that live in them. You can help 

by reducing the amount of water you 

use by taking shorter showers, or 

turning off the faucet while brushing 

your teeth. Learn more by visiting the 

EPA’s Water Sense page at www.epa.gov

/owm/water-efficiency. 

4. Try talking to your school’s principal 

or superintendent about ways to reduce 

the impacts your school has on the 

environment. There are many small 

things your school can do to help 

protect ecosystems. For some ideas, 

check out http://cfpub.epa.gov/schools.

5. Spread the word! Share what you 

have learned about Acid Rain and other 

environmental problems with others. Tell 

them what they can do to protect the 

environment. The more information 

people have, the more they can do to 

make the Earth a cleaner, healthier place. 

Recycling at home is a great way to keep recyclable materials out of landfills.
20

T erminology

Litmus Paper Paper coated with a 

chemical coloring obtained from 

lichens that turns red in acidic 

water and blue in basic water. It 

is used as an acid-base indicator. 

pH Paper Paper that changes color 

to show the pH of a substance. 

Experiments

The answers to all of the questions in 

the experiments section can be found 

at the end of the section, on page 33.

Measuring With 

pH Paper

For most of the following experiments, 

you will need a pH indicator. A pH indicator contains a chemical that changes 

color when it is exposed to acids or 

bases. For example, LITMUS and pH 

PAPER turn red in strong acids and blue 

in strong bases. Because only a few 

pH indicators measure pH over a wide 

range of pH values, you will need to find 

out the pH range of the indicator you 

use. Typically, the color chart provided 

with each pH indicator kit will show 

the pH range of that indicator. Color pH 

indicators provide only an approximate 

measure of the pH, or the strength 

of the acid or base. They are not as 

accurate as pH meters, but they are 

adequate for the following experiments. 

When measuring pH with pH paper or 

litmus paper, dip the end of a strip of 

the paper into each mixture you want 

to test. Follow the directions on the 

package regarding how long you need 

to keep the pH paper in the mixture 

and how long to wait before reading 

the measurement. Then compare the 

color at the wet end of the paper with 

the color chart provided with that pH 

indicator. Write down the pH value and 

color. Always use a clean, unused strip 

of pH paper for each mixture that you 

test. Be sure to conduct the pH test for 

each substance three times, using a 

new pH paper for each test. Record the 

results of each test. If possible, have 

a different student conduct and record 

each test. This helps to ensure scientific 

accuracy, consistency, and replicability.

Measuring With 

pH Meters

A pH meter provides a more precise pH 

measurement than pH paper. Before 

using a pH meter, rinse the electrode 

with distilled water and blot dry with a 

clean paper towel. Calibrate the meter 

according to the directions. When testing 

the pH of a substance, put the electrode 

tip in the mixture and stir once. Be sure 

not to touch the bottom or sides of the 

container. Hold the electrode in the 

mixture for 1 minute or until the reading 

is steady. Record the measurement and 

repeat the test two more times for 

accuracy and consistency.

pH Paper
For more information on measuring 

the pH of soil and water, check out 

the pH protocols defined by GLOBE 

(Global Learning and Observations 

to Benefit the Environment) at 

www.globe.gov/protocols.

Tips

• Except for wide-range pH test paper 

and pH meters, all the materials called 

for in these experiments can be 

obtained at grocery stores or from local 

lawn and garden stores or nurseries. 

• Wide-range pH test paper is pH paper 

that covers the whole pH scale. Not all 

pH test papers do this. Other papers 

cover only part of the pH scale and 

there are different papers to test for 

acids, bases, and neutrals. Both kinds 

are inexpensive, and a school science 

laboratory will probably have one or 

the other, if not both. If the school 

does not already have pH test paper a 

science teacher may know where to 

order it, or you may order it on your 

own through a biological supply 

company. If you have to order pH test 

paper, we recommend wide range pH 

test paper since it can be used for all 

the experiments, and may be less 

confusing to younger students. 

• Baking soda and ammonia are both 

bases. You may substitute baking soda 

for household ammonia in the experiments. If you do, be sure to stir well 

because baking soda does not dissolve 

easily in water unless heated. The pH 

of undissolved baking soda will not be 

the same as dissolved baking soda. 

• Lemon juice and white vinegar are both 

acids. You may substitute freshsqueezed lemon juice for white vinegar. 

Lemon juice is slightly more acidic than 

the vinegar sold in grocery stores. White 

vinegar is preferred over cider vinegar 

or lemon juice because it is colorless 

and relatively free of impurities. 

• Use clean, dry containers and utensils. 

Safety In The 

Laboratory

A science or chemistry laboratory can 

and should be a safe place to perform 

experiments. Accidents can be prevented 

if you think about what you are doing at 

all times, use good judgment, observe 

safety rules, and follow directions.

Always wear protective safety glasses or goggles when working on experiments. 

21
22

• Eye protection (goggles or safety 

glasses) must be worn when working 

on experiments. Make a habit of 

putting them on before the experiment 

begins and keeping them on until all 

clean up is finished. 

• Do not eat or drink while in the 

laboratory. 

• Do not taste any chemical. 

• Long-sleeved shirts and closed-toe, 

leather-topped shoes must be worn at 

all times. 

• Long hair must be tied back, so it will 

not fall into chemicals or flames. 

• Do not work alone; work with an adult. 

• Never perform any unauthorized 

experiment. 

• All glassware must be washed and 

cleaned. Wipe all counter surfaces and 

hands with soap and water. 

• All experiments that produce or use 

chemicals must be done in a wellventilated area. 

• Never point the open end of a test 

tube at yourself or another person. 

• If you want to smell a substance, do 

not hold it directly to your nose. 

Instead, hold the container a few 

centimeters away and use your hand 

to fan vapors toward you. 

• When diluting acids, always add the 

acid to the water; never water to acid. 

Add the acid slowly. 

• Dispose of all chemicals properly, 

according to the directions of your 

teacher.

• If you spill any acid or base material 

on you, wash the exposed area with 

large amounts of cold water. If skin 

becomes irritated, see a physician. 

Recording 

Observations

Writing your observations on these 

experiments will help you to keep 

better track of the progress of the 

experiment and help you to remember 

information for answering questions or 

writing lab reports. Record keeping can 

be very simple and still be a help. These 

hints can help you organize and record 

your thoughts. 

• Use a bound notebook so that pages 

are not lost. 

• Write complete sentences for all 

written entries. 

• Use drawings as needed. 

• Date each entry (even drawings). 

• Use the title of the experiment as your 

first entry. 

• When your observation entries have 

been completed, write your answers 

to the questions that follow each 

experiment. 

• Write your own thoughts about the 

experiment as the conclusion. 

Writing down your observations 

can be very helpful.
Materials

 pH paper and color chart or 

pH meter (pH range 3 to 12) 

 11

/2 cups distilled water

 1/2 teaspoon white vinegar 

 1/2 teaspoon household ammonia 

 3 small cups or beakers

 3 clean stirring spoons 

 measuring cups and spoons 

(1/2 cup and 1/2 teaspoon) 

 notebook and pencil 

Instructions

 Label the first cup “vinegar,” the 

second cup “ammonia,” and the 

third cup “water.”

 Pour 1/2 cup distilled water into 

each of the 3 cups.

 Add 1/2 teaspoon white vinegar 

to the vinegar cup and stir with 

a clean spoon.

 Add 1/2 teaspoon ammonia to 

the ammonia cup and stir with 

a clean spoon.

 Do not add anything to the 

water cup.

  Which substance do you think 

will be an acid? Which one will be a 

base? Take a moment to write down 

your hypotheses.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of the vinegar mixture. Record the pH value.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of the ammonia 

mixture. Record the pH value.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of the distilled water. 

Record the pH value.

 Repeat steps 7-9 two more times so 

you test and record the pH results a 

total of three times for each mixture.

Questions 

1. Is vinegar an acid or a base?

2. Is ammonia an acid or a base? 

3. What is the pH of distilled water? 

Did the pH level surprise you? Why 

do you think distilled water did not 

have a neutral pH? 

4. Were your hypotheses correct?

23

Experiment 

Measuring pH

This experiment 

will illustrate how 

to measure the 

approximate pH of 

chemicals in water 

using a pH indicator. 

This experiment will 

take approximately

20 minutes
24

Materials

 pH paper and color chart or 

pH meter (range pH 2 to 12) 

 3 different fresh, whole fruits 

(lemon, lime, orange, or melon) 

 3 different beverages (cola, 

carbonated non-cola, milk) 

 1/8 teaspoon dish soap or 

laundry detergent 

 1/4 cup distilled water

 measuring cups and spoons 

(1/2 cup, 1/4 and 1/8 teaspoon) 

 4 small cups or beakers

 1 clean stirring spoon 

 notebook and pencil 

 paring knife 

Instructions

 Using the knife, carefully cut each 

fruit in half, cleaning off the knife 

after each cut. 

 Label the 3 cups “cola,” “non-cola,” 

and “milk.”

 Pour about 1/2 cup of each liquid 

into the appropriately labeled cup. 

 In the fourth cup add 1/8 teaspoon 

soap to 1/4 cup distilled water and 

stir for about 2 minutes.

  Given what you have learned, 

which items do you think will be 

acids? Which will be bases? Why? 

Take a moment to write down your 

hypotheses.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of each fruit. Record 

the pH value. Be sure to use a clean, 

unused pH paper for each one or 

clean the pH meter electrode between testing each substance.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of the cola and other 

beverages. Record the pH value. Be 

sure to use a clean, unused strip of 

pH paper for each one or clean the 

pH meter electrode between testing 

each substance.

 Follow the instructions that come 

with your pH paper or pH meter for 

testing the pH of the soap mixture. 

Record the pH value.

 Be sure to conduct the pH test three 

times for each fruit or substance 

and record the results of each test.

Questions

1. Are lemons, limes, oranges, and 

melons acids or bases? 

2. Are colas and non-colas acids 

or bases? 

3. Was the milk acidic or basic?

4. Was the soap/detergent mixture 

acidic or basic?

5. Which item is most acidic? Which 

one is most basic? How can you tell?

6. What other foods or drinks are 

acids? Why?

7. Were your hypotheses correct?

Experiment

Determining The pH Of 

Common Substances

In this experiment, 

you will use a pH 

indicator to measure 

the pH of some fruits, 

common beverages, 

and soaps. Many 

foods and household 

cleaners are either 

acids or bases.

This experiment will 

take approximately

40 minutes
25

Experiment

Making A Natural pH Indicator

Materials

 1 head of red cabbage, sliced 

 stainless steel or enamel pan or 

microwaveable casserole dish 

 1 quart water 

 stove, microwave, or hotplate 

 1/2 teaspoon white vinegar 

 1/2 teaspoon ammonia 

 1 teaspoon clear, carbonated 

beverage, like seltzer water or 

lemon-lime drinks

 3 small clear cups or beakers

 3 clean stirring spoons 

 measuring cups and spoons 

(1 quart, 1/4 cup, 1/2 and 

1 teaspoon) 

 notebook and pencil 

Instructions

 Boil sliced cabbage in 1 quart 

of water in a covered pan for 

30 minutes or microwave for 

10 minutes. (Don’t let the water 

boil away.) 

 Let cool before removing the 

cabbage.

 Label 3 cups “ammonia,” “vinegar,” 

and “beverage.” 

 Pour about 1/4 cup of cabbage juice 

into each cup. 

  What color do you think the 

cabbage juice will turn when you 

add ammonia? What about when 

you add vinegar or the beverage? 

Take a moment to write down your 

hypotheses.

 Add 1/2 teaspoon ammonia to the 

cup labeled “ammonia” and stir 

with a clean spoon. 

 Add 1/2 teaspoon vinegar to the cup 

labeled “vinegar” and stir with a 

clean spoon. 

 Add 1 teaspoon clear non-cola to the 

last cup and stir with a clean spoon. 

 Record and observe what happens to 

the color of the liquid in each cup. 

 After answering the first two 

questions for this experiment, pour 

the contents of the vinegar cup into 

the ammonia cup. 

Questions

1. What color change took place when 

you added vinegar to the cabbage 

juice? Why?

2. Did the ammonia turn the cabbage 

juice pH indicator red or blue? Why?

3. If you were to gradually add vinegar 

to the cup containing the ammonia 

and cabbage juice, what do you 

think would happen to the color 

of the indicator? Try it, stirring 

constantly.

4. Is the non-cola soft drink acidic 

or basic?

5. Were your hypotheses correct?

In this experiment, 

you will make your 

own pH indicator 

from red cabbage. 

Red cabbage contains 

a chemical that turns 

from its natural deep 

purple color to red 

in acids and blue in 

bases. Litmus paper, 

another natural pH 

indicator, also turns 

red in acids and blue 

in bases. 

This experiment will 

take approximately

50 minutes
26

Materials

 pH paper and color chart or 

pH meter (range pH 2 to 7) 

 clean cups or beakers

 2 clean, empty, water or soda bottles

 notebook and pencil 

 A map of the pH of rainwater in the 

United States, which can be found at 

http://nadp.sws.uiuc.edu/isopleths. 

After clicking on annual maps and 

selecting the most recent year 

available, select the report titled 

“Lab pH.” 

Instructions

 Label a clean, empty water or soda 

bottle “rainwater,” and leave it 

outside of your classroom to collect 

water on a rainy day. 

 After you have collected at least a 

tablespoon of water, cap the bottle to 

prevent evaporation and bring it 

inside.

 Locate a local stream, river, lake, or 

pond. Go with an adult. Depending 

on where you live, you may choose 

to gather water samples from many 

sources, including different creeks, 

lakes, ditches, ponds, and rivers.

 Scoop some of the surface water

into a clean, empty water or soda 

bottle. Label the bottle “surface 

water,” and cap the bottle to 

prevent evaporation and spilling 

while you bring it home.

  Do you think the rainwater you 

collected will be acidic? What about 

the different surface water samples? 

Why? Take a moment to write down 

your hypotheses.

 Pour the rain water into a cup and 

measure the pH of the rainwater 

using pH paper or a pH meter and 

record the result. 

 Pour the surface water into a cup 

and measure the pH of the surface 

water using pH paper or a pH meter 

and record the result. 

 Repeat steps 6 and 7 two more 

times so you test and record the pH 

results a total of three times for 

each sample.

Questions

1. What is the pH of the rainwater? 

Compare your results to the map. 

Is it what you expected? 

2. What is the pH of the surface water? 

3. How does the measured pH compare 

to the pH levels that affect plants 

and animals in aquatic habitats? 

(See chart on page 11.)

4. Was one of your samples more 

acidic than the other? Which one? If 

they are different, what do you think 

the reason for the difference is?

5. Were your hypotheses correct?

Experiment

Measuring The pH Of Natural Water

In this experiment, 

you will measure the 

pH of rainwater and 

natural water located 

near your home or 

school. 

T erminology

Surface Water Water that is found 

on the surface of the Earth in 

lakes, ponds, streams, or rivers. 

This

 experiment will 

take approximately

15 minutes in the 

classroom with

additional time for 

water collection
27

Experiment

Measuring Soil pH

Materials

 garden soil pH test kit 

 2 cups soil from each of two or 

three different locations (some of 

the soil will be needed for the “Soil 

Buffering” experiment) 

 measuring spoons 

 digging tool 

 self-sealing plastic bags 

 notebook and pencil 

Instructions

 Pick two or three different soil 

locations, such as a garden, the 

school grounds, a wooded area, city 

park, meadow, etc. Go with an adult.

 At each location, quietly observe the 

plants and animals living in or 

rooted on these soils, especially 

those that are in greatest numbers. 

Write down your observations. 

 Dig down about 2 inches, scoop out 

2 cups of soil, and seal it in a plastic 

bag for later use. Be sure to clean 

your digging tool after collecting soil 

samples at each location.

 Label each plastic bag. 

  What do you think the pH level 

of the soil from each location will 

be? Why? Take a moment to write 

down your hypotheses.

 Back in the classroom, measure the 

pH of each soil sample following the 

directions provided in the garden 

soil pH test kit, and record the 

approximate pH of each soil sample. 

Save the excess soil from each site 

for use in the “Soil Buffering” 

experiment. 

Questions

1. What were the differences between 

the plant and animal life at each 

location? 

2. What was the range of pH levels at 

various sites?

3. Were any of your soil samples acidic?

4. Were any of your soil samples basic?

5. Name some possible reasons for the 

different pH levels at the sites.

6. How do your plant and animal 

observations at each location and 

the pH level of the soil compare to 

the chart on page 11?

7. Were your hypotheses correct?

In this experiment, 

you will collect soil 

and measure its pH. 

Soil pH is one of 

several important 

conditions that 

affect the health of 

plants and animals. 

In addition, you will 

also be asked to 

survey the plants and 

animals that live in 

the area where you 

collected the soil. 

Area surveys provide 

information about 

how well plants 

and animals can 

live under different 

conditions. 

For this experiment, 

you will need an 

inexpensive garden 

soil pH test kit, which 

may be obtained from 

lawn and garden 

stores or nurseries. 

This 

experiment will 

take approximately

20 minutes in the 

classroom with additional 

time for soil sample 

collection
28

Materials

 pH paper and color chart or

pH meter (pH range 2 to 10)

 about 2 cups of soil from a garden, 

wooded area, lawn, or school yard 

 distilled water 

 white vinegar 

 ammonia

 measuring cups and spoons 

(1 cup and 1 teaspoon)

 clean stirring spoon 

 large funnel 

 coffee filters 

 clean cups or beakers

 notebook and pencil 

Instructions

 Pour 1 teaspoon of vinegar into 

1 cup of distilled water. Stir well.

 Check the pH with pH paper or a pH 

meter. The pH of the vinegar/water 

mixture should be about 4. If it is 

below that, add ammonia, stir well, 

and recheck the pH. If it is above pH 

4, add a drop or two of vinegar and 

again recheck the pH. 

 Put 1 coffee filter into the funnel, 

and fill the filter with soil from one 

location. The soil should be slightly 

packed down, so that the water runs 

through it slowly. Dense sandy or 

clay soils might not need to be 

packed down, but this may be 

necessary for looser, loamy soils.

 Hold the funnel over a cup and slowly 

pour the vinegar/water mixture over 

the soil until some water collects in 

the cup. The filter may clog quickly, 

but you need only a small amount of 

water in the cup to test the pH.

  What do you think the pH of the 

water will be after it filters through 

the soil? Why? Do you think it will 

be different for each of the soil 

samples? Take a moment to write 

down your hypotheses.

 Check the pH of the collected water 

using pH paper or a pH meter and 

record the results. 

 Repeat step 4 with the other 

soil samples, washing the funnel 

and using a new coffee filter for 

each sample. 

 Repeat step 6 two more times so you 

test and record the pH results a total 

of three times for each soil sample.

Questions

1. How did the pH of the collected 

water change?

2. Why is it important that soil 

buffer acid?

3. What does acid rain do to soil, and 

why is this a problem?

4. Were your hypotheses correct?

Experiment

Soil Buffering

In this experiment, 

you will find out if 

soil from your lawn, 

garden, or school 

can buffer acids. You 

will observe the pH 

change of an acid 

mixture poured over 

soil in a filter. If the 

water collected from 

the filter is less acidic 

than the original 

mixture, then the soil 

is buffering some of 

the acid. If it does not 

change, then the soil 

may not be capable 

of buffering acids. 

Since the buffering 

capability of soils 

differs, you may want 

to do this experiment 

with several different 

soil types including 

those collected 

for Experiment 5, 

“Measuring Soil pH”. 

This 

experiment will 

take approximately

30-60 minutes 

depending on the

number of soil

samples used
29

Experiment

Observing The Influence Of 

Acid Rain On Plant Growth

Materials

 pH paper and color chart or pH 

meter (pH range 2 to 8)

 3 of the same type of healthy, 

potted plant

 3 one-gallon containers with lids 

(such as a milk jug), one per group 

of three to four students

 1 pint white vinegar

 tap water with a pH of 7

 measuring cup (1 pint)

 notebook and pencil

 poster paper, crayons, markers for 

class presentations

Instructions

 Divide the class into three teams.

 Give each group a 1-gallon container 

(such as a milk container).

 One team will fill their container 

with 1 gallon (3.8 liters) of tap water. 

Label the container “tap water.”

 Another team will fill their container 

with 1 pint (0.5 liters) of vinegar and 

7 pints (3.3 liters) of tap water. Label 

the container “slightly acidic.”

 The third team will fill their container with 2 pints (0.9 liters) of vinegar 

and 6 pints (2.8 liters) of tap water. 

Label the container “very acidic.” 

 Test the pH of each mixture (“tap 

water,” “slightly acidic,” and “very 

acidic”) three times and record 

each result.

 Each team will receive a potted 

plant and label their plant the same 

as their container.

 Each team will be responsible for 

watering their plant from the 

container with the matching label. 

Students should water the plants 

when they need it (every 2-4 days). 

Make sure each group’s plant gets 

the same amount of water in each 

watering cycle. A good way to do 

this is to give each group a cup to 

use when watering.

 Place all three plants in the same 

spot so that they get the same 

amount of light.

  What do you think will happen 

to each plant? Will they differ after 

a few weeks? In what way? Why? 

Take a moment to write down your 

hypotheses.

Have team members examine 

their plants every day and write 

their observations. What do the 

plants look like? What color are 

they? Are the leaves dropping? 

Do they look healthy?

Continue this activity for 2-3 

weeks. Then have students 

examine the plants and discuss 

or give presentations on the 

results of the experiment. 

Questions

1. Do the plants watered with acid 

solutions differ in color or size from 

the others?

2. How long did it take to see the 

effects of each mixture?

3. Which plant showed the most 

effects? Why?

4. Were your hypotheses correct?

Acid rain most often 

damages plants 

by washing away 

nutrients and by 

poisoning the plants 

with toxic metals, 

but it can have 

direct effects on 

plants as well. In 

this experiment, you 

will observe one of 

the direct effects of 

acid rainwater on 

plant growth. The 

experiment will take 

2-3 weeks. 

This

experiment will 

take approximately

20 minutes on day 1,

15 minutes a day to 

record observations,

60-80 minutes for

presentations
30

Materials

 pH paper and color chart or

pH meter (pH range 2 to 7) 

 2 cups or beakers

 2 clean copper pennies (use pennies 

minted before 1983) 

 3 tablespoons white vinegar 

 3 tablespoons distilled water 

 ammonia

 measuring spoon (1 tablespoon)

 plastic wrap 

 notebook and pencil 

Instructions

 Label one cup “water” and the 

other “vinegar”. 

 Put 3 tablespoons of vinegar into 

the cup, enough to cover the 

penny completely. 

 Test the pH of the vinegar and 

record the result.

 Put 3 tablespoons of distilled water 

into the cup, enough to cover the 

penny completely. 

 Test the pH of the distilled water. If 

the pH is below 6, add ammonia and 

recheck the pH. Repeat this process 

until the pH is between 6 and 7. 

Record the pH of the water.

 Repeat steps 3 and 5 two more 

times so you test and record the pH 

results a total of three times for 

each sample.

 Place one penny in each cup. Be 

sure to use pennies minted before 

1983 because pennies minted after 

that time have a different chemical 

composition. 

 Seal the top of each cup with plastic 

wrap to prevent evaporation. 

 Place in a safe, dry place out of 

direct sunlight for about 5 days.

  What do you think will happen 

to the penny in each cup? How will 

they differ? Take a moment to write 

down your hypotheses.

After 5 days, observe the changes 

that occurred in each cup and to the 

penny in each cup.

Questions 

1. What change, if any, took place in 

the distilled water cup and to the 

penny after 5 days? 

2. What change, if any, took place in 

the vinegar cup and to the penny 

after 5 days? 

3. When you rinsed off the pennies, 

were you surprised that they both 

looked about the same as they did 

at the beginning of the experiment?

4. Were your hypotheses correct? 

Experiment

Looking At Acid’s Effects On Metals

When acids and 

metals are exposed to 

each other, the metal 

is gradually dissolved 

away in a chemical 

reaction. In this 

experiment, you will 

observe this reaction 

for yourself, but you 

will need patience. 

The chemical effect of 

acids on metals may 

take at least 5 days 

for the human eye 

to see, even though 

the reaction starts 

as soon as the acid 

contacts the metal. 

This 

experiment will 

take approximately

20 minutes the first day 

and 5-10 minutes each 

additional day
31

Experiment

Observing The Influence Of 

Acid Rain On Marble And Limestone

Materials

 pH paper and color chart or 

pH meter (pH range 2 to 7) 

 2 pieces of chalk

 2 cups or beakers

 plastic wrap

 1/4 cup tap water

 1/4 cup white vinegar 

 measuring cup (1/4 cup)

 notebook and pencil

Instructions

 Label one cup “vinegar” and one 

cup “water.” 

 Pour 1/4 cup vinegar into the cup 

labeled “vinegar.” 

 Test the pH of the vinegar and 

record it. 

 Pour 1/4 cup tap water into the cup 

labeled “water.” 

 Test the pH of the water and record it. 

 Repeat steps 3 and 5 two more 

times so you test and record the pH 

results a total of three times for 

each mixture.

 Place one piece of chalk in each cup. 

If you need to add a little more 

water or vinegar to submerge the 

chalk, do so. 

 Cover each cup with plastic wrap to 

prevent evaporation, and put in a 

safe place overnight. 

  What do you think will happen 

to the piece of chalk in each 

mixture? Why? Take a moment to 

write down your hypotheses.

 The next day, observe the two 

pieces of chalk and record the 

changes that occurred. 

Questions

1. Which piece of chalk is more worn 

away? Why?

2. Have you seen any buildings in 

your town that show evidence of 

acid rain damage? What about the 

grave markers at an old cemetery? 

Would you consider acid rain a 

major problem in your town? Why 

or why not?

3. Have you seen acid rain damage 

on any buildings or monuments in 

other parts of the United States or 

other countries? Describe what you 

saw and where it was. If you do not 

know of any buildings or monuments that have been harmed by 

acid rain, go online and try to find 

some pictures of some.

4. Were your hypotheses correct?

Acids do not just 

eat away at metals. 

They also eat away 

at rocks like marble, 

limestone, and chalk 

that are made of 

calcium carbonate. 

Calcium carbonate 

is also found in 

seashells, bones, and 

teeth. Acids dissolve 

hard rocks, like 

marble, very slowly. 

It can take decades 

for acid rain damage 

to become evident on 

marble structures. 

Soft rocks, like chalk, 

can be dissolved 

much quicker, which 

is why we use it in 

this experiment. In 

this experiment, you 

will observe how acid 

can dissolve calcium 

carbonate.

This experiment will 

take approximately

15 minutes

each day
32
33

Experiment Answers

Below are the answers to the questions 

provided at the end of each experiment.

Experiment 1: Measuring pH 

1. Vinegar is an acid, and in this experiment, it will display a pH of about 4. 

Vinegar at pH 4 turns pH paper yellow 

and most other pH indicators red. 

2. Ammonia is a base and in this 

experiment, it will display a pH of about 

12. Bases turn most pH indicators blue. 

3. Pure distilled water would have tested 

neutral, but pure distilled water is not 

easily obtained because carbon dioxide 

in the air around us mixes, or dissolves, 

in the water, making it somewhat acidic. 

The pH of distilled water is between 5.6 

and 7. You can neutralize distilled water 

by adding about 1/8 teaspoon baking 

soda, or a drop of ammonia, and stirring 

well. Check the pH of the water with a 

pH indicator. If the water is still acidic, 

repeat the process until pH 7 is reached. 

Should you accidentally add too much 

baking soda or ammonia, start over or 

add a drop or two of vinegar, stir, and 

recheck the pH.

4. Answers will vary.

Experiment 2: Determining The 

pH Of Common Substances

1. These fruits all contain acids and taste 

sour. Lemons and limes have pH values 

near 2. Oranges may be slightly less 

acidic than lemons and limes, but your 

pH indicator may not be accurate 

enough to show the difference.

2. They are both acidic, primarily 

because they both contain carbon 

dioxide to make them fizz, and carbon 

dioxide and water produce carbonic 

acid. The pH of these beverages varies 

with the amount of carbon dioxide and 

other ingredients in them, but it is 

usually below 4.

3. Milk can be slightly basic or slightly 

acidic depending on its age and how it 

was processed at the dairy.

4. Soap contains a base and will turn 

most pH indicators blue. Alkaline 

solutions are excellent cleaning agents, 

which is why we use them to wash 

dishes and clothes.

5. Answers will vary. You can tell by 

checking their pH.

6. Answers will vary.

7. Answers will vary.

Experiment 3: Making A 

Natural pH Indicator

1. The vinegar and cabbage juice mixture 

should change from deep purple to red, 

indicating that vinegar is an acid. 

2. The ammonia and cabbage juice 

mixture should change from deep purple 

to blue, because ammonia is a base, 

which reacts chemically with the pH 

indicator, turning it blue. 

3. You should find that the acid and 

base are neutralized, changing the 

color from blue or red to purple, which 

is the original, neutral color of the 

cabbage juice. 
34

4. The non-cola soft drink is acidic and 

turns the cabbage juice pH indicator red.

5. Answers will vary.

Experiment 4: Measuring The 

pH Of Natural Water

1. Answers will vary. 

2. Answers will vary.

3. Answers will vary. See the chart on 

page 11 explaining how acid rain affects 

animals living in the water.

4. The rainwater should be more acidic 

than the surface water from the pond or 

stream. This is because most surface 

water travels through soil and is buff-

ered, or made less acidic, before reach-

ing a pond or stream. It is important to 

note that runoff from agricultural areas 

containing pesticides or fertilizers or 

runoff of industrial pollutants discharged 

(legally or illegally) into streams may 

affect the results of this experiment.

5. Answers will vary.

Experiment 5: Measuring 

Soil pH

1. Some types of plants and animals are 

able to live in acid soils, while others 

are not. Be aware, however, that many 

factors, not just the soil acidity, deter-

mine the types of plants and animals 

that occur at a particular site. 

2. Answers will vary.

3. Some plants require acid soils to grow 

and thrive. For example, pine trees, 

azaleas, rhododendrons, cranberries, 

blueberries, potatoes, and tomatoes 

prefer acid soils. However, most plants 

thrive only in soils of pH 6 to 7. 

4. Some soils, such as in many 

Midwestern states, contain a lot of 

limestone and are alkaline. In those 

locations, people often add sulfate, such 

as ammonium bisulfate to soil to make 

it less basic. 

5. Answers will vary, depending on 

where the soil samples came from. The 

underlying rock can have a large effect 

on soil pH, and so can industrial or 

agricultural runoff in the area.

6. Answers will vary.

7. Answers will vary.

Experiment 6: Soil Buffering 

1. If the pH stayed the same, the soil did 

not buffer the acid. Each pH value above 

4 indicates that the soil buffered increas-

ing amounts of the acid. 

2. Not all plants and animals can live in 

acidic soil, so by buffering the acid the 

soil makes the environment more 

habitable. 

3. Even soil capable of buffering acids 

can be overpowered if enough acid is 

added. As more acid is added to the soil 

by acid rain, the buffering capability 

decreases, and the soil becomes more 

acidic. This can hurt delicate ecosystems 

like forests.

4. Answers will vary.
35

Experiment 7: Observing The 

Influence Of Acid Rain On 

Plant Growth

1. The plants watered with acidic 

solutions will not do as well as the 

plants watered with clean water. Some 

effects of the acidic solution on plant 

growth are withering or drooping leaves, 

change in leaf color, and stunted growth.

2. The effects of the very strong acidic 

solution on the plants should be visible 

within a few days. The less acidic 

solution may not affect the plant for a 

week to a week and a half. The degree 

to which the plant is affected by the 

acid depends on the health of the plant 

and the hardiness of the species.

3. The plant watered with the very acidic 

solution should exhibit significantly 

more damage than the plant watered 

with the weaker acidic solution.

4. Answers will vary.

Experiment 8: Looking At 

Acid’s Effects On Metals

1. There should be no change. 

2. The liquid should be bluish-green. The 

bluish-green substance in the vinegar 

comes from the copper in the penny. It 

is a byproduct of the chemical reaction 

in which the acid in the vinegar gradually eats away the penny. 

3. The chemical reaction between the 

acid and the copper penny is so slow 

that you cannot see any difference in 

the shape of the metal in just 5 days, at 

least not with your eye alone. You may 

see some changes after about 2 weeks, 

especially at the edge of the penny.

4. Answers will vary.

Experiment 9: Observing The 

Influence Of Acid Rain On 

Marble And Limestone

1. The chalk in the vinegar should be 

significantly more worn away then the 

piece of chalk in the distilled water. This 

is because the acid dissolves the 

calcium carbonate in the chalk. 

2. Answers will vary. 

3. Answers will vary. 

4. Answers will vary.
36
37

• Join GLOBE (Global Learning and 

Observations to Benefit the 

Environment) at www.globe.gov. 

Collect data on the pH of rain, 

surface water, and soil according to 

GLOBE’s protocols and post your 

results on GLOBE’s online database. 

Compare your results to other 

student’s results in the United 

States and around the world.

• Role play different characters involved 

in or affected by acid rain. Each 

person in the class takes the role of 

an interested party (for example a 

fish, bird, coal miner, farmer, factory 

owner, power company, stream, lake, 

tree, etc.). With each student or 

group playing a character, have a 

group discussion or debate on acid 

rain. Tell the rest of the class how 

acid rain affects your character, and 

then present an argument for or 

against laws that control acid rain. 

• As individuals, contact your local 

power company. If you have a large 

class, you may also want to assign 

some students to research power 

companies from other parts of the 

country. Many power companies use 

more than one source of power to 

make enough electricity for the 

community. Some also buy electricity 

from other power companies. Ask 

the power company what sources of 

energy it uses (hydroelectric, nuclear, gas, oil, coal, other) and what 

percentage of their energy output 

comes from each source. Write down 

results to report to the class. 

• In small groups or as individuals, 

write, produce, and direct a special 

segment for a TV weather special 

on the effect of weather patterns on 

the travel of air pollution over large 

distances. Contact the weather bureau or a local TV station’s weather 

department to ask about the wind 

patterns in your area. Use the EPA 

Clean Air Market Division’s data and 

maps Web site (http://camddata

andmaps.epa.gov/gdm/) to find 

power plants and their emissions in 

your area. The EPA’s C-MAP Web site 

(www.epa.gov/airmarkets/maps

/c-map.html) is another online tool 

that you can use to perform this 

activity. Map where you think pollution from local power plants may 

end up. Discuss what communities, 

cities, ecosystems, parks, schools, 

etc. may be affected.

Activities

Here are some sug

gested interdisciplin

-

ary activities, projects, 

-

and field trips to 

enhance students’ 

understanding of the 

sources and effects of 

acid rain.

This power plant in Tennessee uses hydroelectric energy to produce electricity.
38

• Learn how EPA regulates the 

emissions that cause acid rain. EPA 

has several programs that control 

emissions. Research the Acid Rain 

Program, NOX State Implementation 

Plan (SIP) Call, NOX Budget Trading 

Program, or the Clean Air Interstate 

Rule (www.epa.gov/airmarkets). 

Write a report on what pollutants 

these programs regulate and how 

they regulate them.

• Invite a local natural resource 

specialist from a zoo, aquarium, 

nature center, or national/state park 

to come in and speak to your class 

about the effects of acid rain on 

animals and their habitat. You could 

also telephone natural resource 

specialists around the country. 

Interview the specialist and ask 

them to tell you about the impact of 

acid rain and dry deposition on the 

lakes, forests, or other natural 

resources in your area. Write down 

what you have learned in a report. 

• EPA has regional offices around the 

nation. Contact your regional EPA 

office, and ask a representative from 

EPA to visit your class. Prepare for 

their visit by brainstorming interview 

questions to ask them when they 

visit. You may want to ask them 

about the effects of acid rain in your 

region of the country, or what other 

environmental issues they believe 

are most pressing in your region. 

When they come to class, take turns 

asking questions, and write a 

newspaper article about the interview. The locations of EPA regional 

offices and contact information can 

be found online at www.epa.gov

/epahome/locate2.htm. 

• Call or visit your local water company. Ask them where your water 

comes from: a well, lake, reservoir, or 

river. If you have a private well, ask 

your parents if the water is treated 

for acidity, and if so, how. When 

talking to the water company, ask 

how they treat the water for acidity. 

Ask if they can tell you the pH of the 

water before it is treated, and after it 

is treated. Is it completely neutralized? Write down their answers in a 

report to give to the class. 

• Contact a local architecture firm, 

an architecture department at a 

local university, a member of a state 

or national Green Building Council, 

or the EPA Energy Star® program, 

and see if you can get someone to 

visit your classroom and describe 

how homes, schools, and office 

buildings can use energy and 

resources more efficiently. 

Contact your local water 

company to find out where 

your water comes from.

Contact a local natural resource specialist and have them come in to speak about 

the effects of acid rain on animals and their habitat.
39

Crossword Puzzle

Directions

Read each clue below then find the 

number in the puzzle that corresponds 

to each clue. To assist you, there is a list 

of possible answers to each clue below 

the puzzle. Now it is time to see how 

many clues you can get correct!

Across

3. A solution is __________ when it has 

a pH higher than 7.0.

5. When power plants burn _________, 

they release sulfur dioxide and 

nitrogen oxides into the air.

7. Wet __________ refers to acidic rain, 

fog, and snow.

9. __________ deposition can be wet 

or dry.

11. You can __________ acidic water by 

adding a base.

13. A __________ removes sulfur dioxide 

from the gases leaving the smokestack of a power plant.

Down

1. The government gives an __________ 

to a power plant, letting it release a 

set amount of sulfur dioxide.

2. One way that people can help 

prevent acid rain is by joining a 

__________, in which individuals 

share rides to their destination and 

reduce the number of cars polluting 

the air.

4. __________ is to turn from gas or 

vapor into liquid form.

6. An __________ consists of plants 

and animals and the environment in 

which they live.

8. Sulfur dioxide, nitrogen oxides, 

ozone, and particulate matter are 

examples of __________.

10. Hydroelectricity is produced from 

the energy of running __________.

12. Solar energy is energy that comes 

from the __________.

Possible Answers

Acid

Allowance

Basic

Carpool

Coal

Condense

Deposition

Ecosystem

Neutralize

Pollutants

Scrubber

Sun 

Water

Games
40

o a p q o l a c i m e h c p j u j

i n a n x f m u n j q h v g i h g

j l m s o z h i b a s i c e x y c

d s l e n i a c l i h r h o n d t

e n c x t q t q z v d a j t p r n

c o o r m s r a h f x t n h d o o

n i p d u z y v c v m b t e a p i

a t b u f b y s c i u q c r a o t

w i s r y w b y o f f l s m c w u

o s r d y r b e f c x i j a i e l

l o s x y o l e r g e x d l d r l

l p h p t o r r o s v t a i i p o

a e s n o i s s i m e w p p c d p

s d n p l e a c h i n g q l t a g

z c r y t a z h x m n g x i u w o

f a h p x r a l n z w C A P e x x

c i a m c o a l h q g q d d b o k

Word Search

Directions

All words that are listed below are hidden in the collections of scrambled letters. 

Your goal as an acid rain detective is to find as many words as possible. Look very 

carefully — the words can go forwards, backwards, up and down, and diagonally. 

How good are your detective skills?

F ind words

Acidic

Allowance

Basic

Buffer

Cap

Carpool

Chemical

Coal

Deposition

Ecosystem

Emissions

Geothermal

Hydropower

Pollution

Scrubbers
41

Game Answers

B A s i c

l

l

o

w

A

n

c

e

c i d

d e p s i t i o n

c

n

d

e

n

s

e

c o a l

c

r

p

o

o

l

e

c

o

s

y

s

t

e

m

n u t r a l i z e

o

l

l

u

t

n

t

s c r u b b e r

p

s

n

w

a

t

r
42

Readings 

Parks, Peggy J. Acid Rain (Our 

Environment Series). Detroit [MI]: 

KidHaven Press, 2006. Ages 12 and up. 

Petheram, Louise. Acid Rain. Mankato 

[MN]: Capstone Press, 2002. Ages 8 to 9.

O’Connor, Rebecca K. Acid Rain (Lucent 

Overview Series). Farmington Hills [MI]: 

Lucent Books, 2003. Ages 12 and up. 

Allaby, Michael. Fog, Smog, and Poisoned 

Rain (Facts on File Dangerous Weather 

Series). New York [NY]: Facts on File, May 

2003. Ages 11 and up.

Johnson, Rebecca L. Acids and Bases 

(Physical Science Series). New York: 

National Geographic, 2004. Ages 9 

through 13.

Web sites

EPA has information on acid rain and 

other air quality issues at www.epa.gov

/airmarkets/index.html.

Find resources and activities on EPA’s 

general site for teachers and students 

at www.epa.gov/region5/teachers.

The EPA’s Acid Rain for Kids site can be 

accessed at www.epa.gov/acidrain

/education/site_kids. 

The Acid Rain Program Annual Reports are 

available online at www.epa.gov/airmarkets

/progress/progress-reports.html. 

The U.S. Geological Survey Web site has 

an acid rain page at http://ga.water.usgs

.gov/edu/acidrain.html. 

The National Park Service has a great 

students and teachers Web site at http://

www2.nature.nps.gov/air/edu/index.cfm.

The Geological Society of America has 

information on several environmental 

issues at www.geosociety.org /educate

/LessonPlans/i_water.htm.

The National Atmospheric Deposition 

Program site has some more information 

for teachers or older students, including 

links to data and maps at http://nadp

.sws.uiuc.edu/. It also has a page that 

links to several good online resources 

for all ages at http://nadp.sws.uiuc.edu

/cal/Educational_Information.htm.

The National Oceanic and 

Atmospheric Administration has a 

students and teachers resource page at 

http://oceanservice.noaa.gov/kids.

You can look at acid rain data collected by 

students around the world, or even 

upload your own on the GLOBE Web site 

at www.globe.gov/fsl/welcome.html.

Audiovisuals 

Acid Rain (DVD) Educational Video 

Network, Inc., 2004. Run Time: 

20 minutes.

Air Pollution, Smog, and Acid Rain (DVD) 

Educational Video Network, Inc., 2004. 

Run Time: 21 minutes.

Additional Resources
43

Acid Any of a large group of chemicals 

with a pH less than 7. Examples are 

battery acid, lemon juice, and vinegar.

Acidic Describes a substance with a pH 

less than 7.

Acid Deposition Acidic material that falls 

from the atmosphere to the Earth in 

either wet (rain, sleet, snow, fog) or dry 

(gases, particles) forms.

Acid Rain Rain that has become acidic 

by contact with air pollution. Other 

forms of precipitation, such as snow and 

fog, are also often included in the term 

acid rain or acid wet deposition. 

Allowance The permission, given by the 

government, to emit a certain amount 

of sulfur dioxide (SO2) or nitrogen 

oxide (NOx).

Aluminum A silvery-white metal; it is 

the most abundant metal in the 

Earth’s crust.

Aquatic Relating to water.

Atmosphere The air or gases that 

surround a planetary body such as 

the Earth. 

Atmospheric Relating to the atmosphere, 

or the air above the Earth. 

Base Any of a large group of chemicals 

with a pH greater than 7. Examples are 

ammonia and baking soda.

Basic Describes a substance with a pH 

greater than 7. Another word for basic 

is alkaline.

Buffer A substance, such as soil, 

bedrock, or water, capable of 

neutralizing either acids or bases. 

Buffering Capacity The ability of a 

substance to resist changes in pH when 

acids or bases are added. 

Cap A national limit that is placed on 

the amount of a pollutant that can be 

emitted. The cap is very important 

because it makes sure that emissions of 

a pollutant are reduced.

Cap and Trade An environmental policy 

tool that controls large amounts of 

emissions from a group of sources. Cap 

and trade programs set a cap, or limit, 

on emissions. Then allowances for 

emissions are traded between sources, 

so that economic market forces allow 

large emissions reductions to be costeffective. 

Carbon Dioxide (CO2) A naturally 

occurring gas made carbon and oxygen. 

Sources of carbon dioxide in the 

atmosphere include animals, which 

exhale carbon dioxide, and the burning 

of fossil fuels and biomass.

Condense To change from gas or vapor 

to liquid form. 

Deposition When chemicals like acids or 

bases fall to the Earth’s surface. 

Deposition can be wet (rain, sleet, snow, 

fog) or dry (gases, particles).

Dry Deposition The falling of small 

particles and gases to the Earth without 

rain or snow. 

Glossary
44

Ecology The study of ecosystems. 

Someone who studies ecology is called 

an ecologist. 

Ecosystem All the living and nonliving 

things in an area, as well as the 

interactions between them. 

Emissions The gases that are released 

when fossil fuels are burned. 

Energy Resources Natural resources that 

can be used to make heat, electricity, or 

any other form of energy. The most 

commonly used energy resources are 

fossil fuels (coal, oil, and gas), but the 

sun, wind, and anything else that makes 

energy are also energy resources.

Environment The air, water, soil, 

minerals, organisms, and all other 

factors surrounding and affecting an 

organism. 

Evaporate To change from liquid 

into gas.

Fossil Fuels Oil, natural gas, and coal. 

Fossil fuels were made in nature from 

ancient plants and animals, and today 

we burn them to make energy.

Fuel Cells Similar to batteries, fuel 

cells store energy that can be used to 

power all sorts of things. Unlike a 

battery though, fuel cells do not “run 

out” and do not need to be recharged 

or replaced.

Greenhouse Gases Gases that occur 

naturally in the Earth’s atmosphere and 

trap heat to keep the planet warm. 

Some examples are carbon dioxide, 

water vapor, halogenated fluorocarbons, 

methane, hydrofluorocarbons, nitrous 

oxide, perfluoronated carbons, and 

ozone. Some human actions, like the 

burning of fossil fuels, also produce 

greenhouse gases. 

Habitat The place where a plant or 

animal lives and grows, such as a forest, 

lake, or stream. 

Haze When particles of dust, pollen, or 

pollution make the air less clear, and 

limit visibility.

Hydroelectric Power Energy that is 

generated by dams, which use water to 

turn turbines and generate electricity.

Hydrologic Cycle The movement of water 

from the atmosphere to the surface of 

the land, soil, and plants and back again 

to the atmosphere. 

Litmus Paper Paper coated with a 

chemical coloring obtained from lichens 

that turns red in acidic water and blue 

in basic water. It is used as an acid-base 

indicator. 

Meteorological Pertaining to the weather.

Natural Resources All the parts of the 

Earth that are not human-made and 

which people use, like fish, trees, 

minerals, lakes, or rivers. 
45

Neutral A substance that is neither an 

acid nor a base and has a pH of 7. 

Neutral substances can be created by 

combining acids and bases. 

Neutralize To combine acids and bases 

to make a neutral substance or solution. 

For example, acidic water can be 

neutralized by adding a base. 

Nitric Acid An acid that can be produced 

from nitrogen oxide, a pollutant that 

results from the burning of fossil fuels. 

Nitrogen Oxides (NO

x) A family of 

gases made up of nitrogen and 

oxygen commonly released by 

burning fossil fuels. 

Nuclear Power Energy that comes from 

breaking apart the center (nucleus) of 

an atom. 

Nutrient Deficiency When a living thing 

lacks the vitamins and minerals it needs 

to survive.

Ozone A chemical that is made of three 

oxygen atoms joined together, and found 

in the Earth’s atmosphere. There are two 

kinds of ozone: good ozone, and bad 

ozone. Good ozone is found high in the 

Earth’s atmosphere, and prevents the 

sun’s harmful rays from reaching the 

Earth. Bad ozone is found low to the 

ground, and can be harmful to animals 

and humans because it damages our 

lungs, sometimes making it difficult to 

breathe.

Ozone Layer The layer of ozone that 

shields the Earth from the sun’s 

harmful rays.

Particulate Matter Tiny solid particles or 

liquid droplets suspended in the air.

pH Paper Paper that changes color to 

show the pH of a substance. 

pH Scale The range of units that 

indicate whether a substance is acidic, 

basic, or neutral. The pH scale ranges 

from 0 to 14. 

Photosynthesis The process that plants 

use to convert sunlight to energy to live 

and grow. 

Pollutants Chemicals or other substances 

that are harmful to or unwanted in the 

environment. Some examples of 

pollutants are sulfur dioxide (SO

2), 

nitrogen oxides (NO

x), ozone, and 

particulate matter.

Pollution The release of harmful 

substances into the environment.

Precipitation Water falling to the Earth. 

Mist, sleet, rain, hail, and snow are the 

most common kinds of precipitation. 

Primary Producers Organisms that use 

photosynthesis to produce their own 

food. All plants are primary producers. 

Primary producers are the base of the 

food chain because they feed 

everything else. 

Reactive Having the tendency to 

chemically combine with something 

else and change its form. For example, 

a strong acid is highly reactive with a 

strong base. 
46

Respiratory Illness Diseases affecting the 

organs we use to breathe. Asthma, 

bronchitis, and pneumonia are examples 

of respiratory illnesses.

Respiratory System The organs in our 

body involved with the process of 

breathing.

Runoff Water that flows off land into 

lakes and streams. 

Scrubber A device that removes air 

pollution, mainly sulfur dioxide, from 

smokestacks. 

Solar Power Electricity that is generated 

by harnessing the energy of the sun. 

Solar panels are often used to convert 

sunlight to energy.

Sulfur Dioxide (SO2) A naturally occurring 

gas made of sulfur and oxygen that is 

also released when fossil fuels are 

burned. 

Sulfuric Acid An acid that can be 

produced in the atmosphere from sulfur 

dioxide, a pollutant that results from 

burning fossil fuels. 

Surface Water Water that is found on the 

surface of the Earth in lakes, ponds, 

streams, or rivers. 

Turbine A motor activated by water, 

steam, or air to produce energy.

Wind Power Energy that is generated 

when the wind turns the sails of a 

windmill, which are attached to turbines 

that generate electricity. 
Certificate of Achievement

This certificate is awarded to

___________________________________________________________

For participation and completion of

The Acid Rain Awareness Program

___________________________

Teacher Signature

___________________________

Date


United States Environmental Protection Agency

Office of Air and Radiation

Office of Atmospheric Programs

Clean Air Markets Division (6204J)

1200 Pennsylvania Ave., NW

Washington, D.C. 20460

EPA 430-F-08-002

April 2008