3 13 so much energy (physical science)

Vocabulary absorb electric charges electric circuits electric current kinetic energy potential energy refl ect refract thermal energy Picture Credits Every effort has been made to secure

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Scott Foresman Science 3.13

Nonfi ction Main Idea and

Supporting Details

• Captions

• Labels

• Glossary

Energy

ISBN 0-328-13845-2

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Scott Foresman Science 3.13

Nonfi ction Main Idea and

Supporting Details

• Captions

• Labels

• Glossary

Energy

ISBN 0-328-13845-2

ì<(sk$m)=bdiefg< +^-Ä-U-Ä-U

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1 Why does light refract?

2 Where do you get potential energy?

3 What are two examples of

the Sun’s energy?

4 In this book

you have read about waves and energy Write to explain how you can tell if a wave has a lot of

energy or a little energy Use

the words trough and crest in

your answer

5 Main Idea and Supporting Details Electrical charges can be

positive or negative What details from the book help you understand how charges move?

What did you learn?

Vocabulary

absorb

electric charges

electric circuits

electric current

kinetic energy

potential energy

refl ect

refract

thermal energy

Picture Credits

Every effort has been made to secure permission and provide appropriate credit for photographic material

The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

6 Getty Images; 8 Getty Images; 9 Kindra Clineff/Index Stock Imagery; 10 VCL/Spencer Rowell/Getty Images; 14 Getty

Images; 16 David Wrobel/Visuals Unlimited; 21 Digital Vision.

Scott Foresman/Dorling Kindersley would also like to thank: 1, 13 Marconi Instruments Limited/DK Images; 19, 22 (R)

Stephen Oliver/DK Images.

ISBN: 0-328-13845-2

This publication is protected by Copyright, and permission should be obtained from the publisher prior to any

prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,

mechanical, photocopying, recording, or likewise For information regarding permission(s), write to

Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

by Margo Tong

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Suppose you and your family are going to

spend a day at the beach All of you get up early,

put on your swimsuits, and eat breakfast You

pack some towels, beach chairs, an umbrella, and

beach toys Everyone puts on hats and sunglasses

You put all the things you need into the car, and

you’re off!

Your parents park the car at a beach parking

lot You walk to the beach, where you fi nd the

perfect place on the warm sand There you

spread out the towels, set up the chairs, and open

the umbrella You take out your toys and start

digging in the sand You are ready

to have fun

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The Sun is Earth’s main source of energy.

You use a lot of energy to get to the beach

Energy is the ability to do work or cause change

Nothing happens without energy Much of what

we know about the universe comes from the study of energy There are many forms of energy and many ways to transmit energy There are many ways to change energy, and many ways to store energy

The Sun is the main source of energy for Earth Keep reading to fi nd out how its energy powers and shapes life on Earth!

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The Sun’s energy has different forms One

form is heat Heat energy is created by reactions

inside the Sun Heat travels to the Sun’s surface

and then to Earth It causes ice to melt and water

to evaporate The uneven heating of Earth’s land

and air causes wind, rain, and other forms of

weather

Light is another form of energy from

the Sun Like heat energy, it is created

inside the Sun and then travels to

Earth Light energy helps plants

grow There would be no life on

Earth without heat energy and

light energy

There are other kinds of energy You probably used some energy this morning Did you turn on

a light when you got up? If you did, the light used electrical energy The food you ate for breakfast has chemical energy If you listened to the radio, you used sound energy Your family used the mechanical energy of the car to get to the beach

Many of the energies listed are combined with other energies For example, a light wastes some energy That wasted energy is heat energy To turn

on the radio and use its sound energy, you need

to use electrical energy And the chemical energy created by the gas in a car gives it the mechanical energy needed to drive

Eating breakfast gives us energy.

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What is stored energy?

Do you like to swim when you are at the

beach? If you do, you will need to use energy

stored in your body Stored energy is potential

energy. It is inside both people and things,

waiting to be released Whenever an object is at

rest, it has potential energy The object uses its

potential energy when it starts moving

An example of an object with potential energy

is a rollercoaster sitting at the top of a hill The

rollercoaster uses its potential energy as soon as

it starts moving downhill

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Potential energy changes to a form of energy

to do work or to cause change For example, the stored energy in your body is chemical energy It comes from the energy in food Airplanes also use chemical energy It is released when jet fuel is burned

Work has to be done to change potential energy In the case of the rollercoaster, gravity works to make it roll downhill In the case of the food you eat, your body works on it to change it

to chemical energy

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Are you ready for that swim? The minute you

start to swim you have kinetic energy, the energy

of motion Everything that moves has kinetic

energy Buses, spinning tops, running animals, and

other moving things all have kinetic energy

Friction goes against kinetic energy, changing it

to heat Without a new source of kinetic energy,

all objects in motion eventually come to a stop

What is energy of motion?

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Playing and swimming are forms of kinetic energy.

Fast-moving water has a lot of kinetic energy

Many years ago, people fi gured out a way to use that energy They built dams to speed up the fl ow of river water The water was used

to power waterwheels The waterwheels were part of factories built along riverbanks The kinetic energy of the water turned the wheels

The wheels were attached to factory equipment inside The equipment worked because it used kinetic energy created by the moving water

More recently, people fi gured out how to make electricity from moving water They built dams that create electricity These dams change water’s kinetic energy to electrical energy

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Changing Forms

of Energy

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Energy can change from one form to another

This morning you ate some cereal The chemical

energy from the cereal was stored as potential

energy in your body That potential energy was

changed to kinetic energy when you took a swim

You can get more potential energy by eating lunch

Whenever energy changes form, some of the

energy is given off as heat Your body got warmer

when it changed the cereal’s chemical energy

to kinetic energy

During your swim, some of that kinetic energy heated the surrounding water

Your day at the beach

is over You have gone home You have had dinner and are ready to watch television You take the stored chemical energy from dinner and turn it into kinetic energy when you press the remote control

The remote control uses several forms of energy Its batteries use chemical energy to create

an electric current The current is electrical energy It creates a beam of light that travels from the remote to the television The beam is light energy It turns on the television

The television releases sound and light energy

There is just a little bit of heat coming from the television, too

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Eating lunch gives you potential energy.

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You know that moving objects contain

energy But did you know that some energy

travels as waves? Sometimes these waves

are easy to see, such as ocean waves or

ripples of water The bigger the wave or

ripple, the more energy it carries

Some other forms of energy, such as

sound, also move as waves You cannot see

these waves without special equipment

How does energy travel?

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You can measure how much energy is in a wave The bottom of a wave is called a trough The top

of a wave is called the crest, or peak Wide waves have lots of space between the trough and crest

They also have lots of energy

The length of an energy wave can be measured too Find the space between two crests The

shorter the space, the more energy that wave has

Short waves have more energy than long waves

That’s why a shortwave radio can pick up sounds from very far away

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trough

crest

Sound waves

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The very tiny particles that make up all

three forms of matter are also moving They are

moving because they have energy This energy

is called thermal energy Every time these tiny

particles move, they give off some heat

Heat Energy

Melted chocolate

Ice cubes

Feel the top of a computer after

it has been on for a while It will feel very warm The computer’s electrical energy is giving off heat

If you put a sheet of paper on top

of the computer, it will pick up some

of the heat Thermal energy moves as heat from a warmer object to a cooler object The paper will not get warmer than the computer It will only get as warm as the computer

Thermal energy can change matter

If you take away enough heat from a liquid, you can freeze it If you add enough heat

to a solid, you can melt it

Chocolate

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Light is energy that we can see The Sun

produces light every day Electricity is another

source of light Light can also be made during

chemical changes When fuel is burned, both

heat and light are created A fi re in a fi replace

keeps you warm It also gives off a nice glow

Chemical changes in some living things also

make light Some ocean fi sh make their own

light because of chemicals in their bodies It

is very dark deep in the ocean The light some

ocean fi sh make helps them see The lantern fi sh

got its name because it makes light in its body

The light attracts both prey and mates

Light Energy

Lantern fi sh

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Light takes the shortest and simplest path from one point to another Light does not turn around corners An object that blocks light will cast a shadow behind it

Not all objects block out light Light can pass through glass and clear water

Scientists use different terms to describe light

What path does light take?

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Making shadows

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Even though light cannot avoid hitting an

object, it keeps moving after it does Objects

refl ect or redirect light Objects with fl at, smooth

surfaces refl ect light very well Light that bounces

off an object keeps moving, but in a different

direction A mirror does this You can see your

own refl ection in a mirror because a lot of light

refl ects off your face If the light is right, you

might see yourself refl ected in a lake too

How does light change?

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Objects that refract, or bend light, usually

make things appear differently from the way they normally do Things can look bigger or smaller than they really are They can look longer, shorter, thinner, or wider too

Light refracts because it moves at different speeds through different materials For example, light moves more quickly through air than it does through water

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Did you know that sunlight is made of

different colors? Red, orange, yellow, green,

blue, indigo, and violet are all found in sunlight

Sometimes refraction causes the light to

separate into these colors That’s when

you can see a rainbow

When light hits an object, it will

refl ect at least one of these colors

Suppose a book has a blue cover in

the sunlight This means the book

is refl ecting blue light

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The book does not refl ect colors other than blue

It absorbs them, or takes them in A white object

refl ects all the colors of sunlight A black object absorbs all the colors Have you ever noticed that dark objects feel hotter in sunlight? That’s because

a lot of the absorbed sunlight turns into heat

Polar bears refl ect and absorb sunlight Their fur looks white because it refl ects some of the sunlight However, underneath their fur polar bears have black skin that absorbs the rest of the Sun’s light and changes it to heat This is part of the way that polar bears stay warm during cold arctic winters

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The particles that make up matter have both

negative and positive electric charges An

electric charge is a tiny amount of energy

An object can be positively charged or

negatively charged Positively charged objects

attract negatively charged ones This means

that positively charged particles pull negatively

charged ones toward themselves Objects with the

same charge repel one another This means two

negatively charged particles will push each other

away

Positive and negative charges

are everywhere Magnets have

positive and negative charges

Lightning is caused by

positive and negative

charges Even your body

contains substances

that are positively and

negatively charged

Electrical Energy

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An electric current is

the fl ow of electric charges from one place to another

Electric circuits are pathways that

control the fl ow

of the current

Circuits are usually made with metal wires This

is because metals are very good at moving electricity from one place to another When you

fl ip a switch, you are closing a circuit Once the circuit is closed, the electric current fl ows

The electricity that runs through your home travels on an alternating current Alternating currents change direction at certain times

Some industries use direct current, which does not change direction

Electricity powers many of the everyday objects we use How many can you name?

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absorb take in or suck up

electric charges tiny amounts of energy

electric circuits controlled pathways that

electric charges travel on

electric current the movement of

electrical energy

kinetic energy the energy of motion

potential energy energy stored in objects

and living things

go in a different direction

direction

thermal energy the total energy of all

the particles in matter

Glossary

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