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Written by Felicia Brown

Heat EnergyA Science A–Z Physical Series

Word Count: 1,301 Heat Energy

Heat EnergyKey elements Used in this BooK

the Big idea: One of the most important types of energy on Earth is heat energy. A great deal of heat energy comes from the Sun’s light hitting Earth. Other sources include geothermal energy, friction, and even living things. Heat energy is the driving force behind everything we do. This energy gives us the ability to run, dance, sing, and play. We also use heat energy to warm our homes, cook our food, power our vehicles, and create electricity.Key words: cold, conduction, conductor, convection, energy, evaporate, fire, friction, fuel, gas, geothermal heat, geyser, heat energy, hot, insulation, insulator, lightning, liquid, matter, particles, radiate, radiant energy, solid, Sun, temperature, thermometer, transfer, volcano

Key comprehension skill: Cause and effectOther suitable comprehension skills: Compare and contrast; classify information; main idea and details; identify facts; elements of a genre; interpret graphs, charts, and diagram

Key reading strategy: Connect to prior knowledgeOther suitable reading strategies: Ask and answer questions; summarize; visualize, using a table of contents and headings; using a glossary and bold terms

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Heat Energy © Learning A–Z Written by Felicia Brown

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Written by Felicia Brown

Photo Credits: Front cover: © iStockphoto.com/Julien Grondin; back cover, page 5: © iStockphoto.com/Arpad Benedek; title page, page 20 (top): © iStockphoto.com/Anna Ziska; pages 3, 9, 20 (bottom): © Jupiterimages Corporation; page 4: © iStockphoto.com/Nancy Louie; page 6 (left): © iStockphoto.com/Sreedhar Yedlapati; page 6 (right): © iStockphoto.com/ Diane Diederich; page 7 (left): © iStockphoto.com/Allen Johnson; page 7 (right): © iStockphoto.com/Alexander Hafemann; pages 10, 11: © iStockphoto.com/bubaone; page 13: © iStockphoto.com/Milorad Zaric; page 16 (top): © iStockphoto.com/Mik111; page 16 (bottom left): © iStockphoto.com/Amanda Rohde; page 16 (bottom right): © iStockphoto.com/Craig Veltri; page 21 (top): Sheryl Shetler/© Learning A–Z; page 21 (bottom): © iCLipART.com; page 22: courtesy of NASA/JpL-Caltech

illustration Credits: pages 8, 12, 14, 15, 17, 18, 19: Cende Hill/© Learning A–Z

Table of Contents

Introduction............................................... 4.

Sources.of.Heat.Energy............................ 5

Temperature............................................. 10

Heat.Moves.Through.Things................ 13

Conduction............................................... 14

Convection............................................... 17

Heat.Energy.and.You.............................. 20

Glossary.................................................... 23

Index......................................................... 24

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Introduction

Have.you.ever.stood.next.to.a.campfire?.Have.you.ever.watched.soup.boil.or.ice.melt?.If.so,.you.have.seen.or.felt.heat

energy.at.work!

There.are.many.kinds.of.energy,.such.as.sound.energy.and.electrical.energy..But.it.is.heat.energy.that.you.see.and.feel.the.most..We.use.it.to.cook.our.food,.heat.our.houses,.and.run.our.cars.

In.this.book,.you.will.learn.where.heat.energy.comes.from,.how.it.is.used,.how.it.moves,.and.more.4

Heat energy cooks these marshmallows.

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Burning.fuel.is.another.way.we.make.heat..When.fuels.like.coal,.gasoline,..and.wood.burn,.they.make.heat.energy..Heat.from.burning.gasoline.is.used.to.make.cars.and.trucks.drive..

Electricity.is.another.way.we.get.heat.energy..Toasters,.irons,.and.hair.dryers.are.just.a.few.things.that.use.electricity.to.make.heat..Electric.furnaces.heat.homes.and.schools.

Rubbing your hands and wearing warm clothing help keep you warm.

Fuel makes cars run and makes electricity we use every day.

Sources of Heat Energy

Have.you.ever.wondered.about.all.the.ways.we.get.heat.energy?

One.easy.way.to.make.heat.is.with.friction,.or.the.rubbing.together.of.two.objects..Rub.your.hands.together.very.fast..Can.you.feel.the.heat?.Rough.objects.often.make.more.friction.than.smooth.objects,.and.more.friction.makes.more.heat!

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The.Sun.is.our.most.important.source..of.energy..Have.you.ever.stepped.from.the.shade.into.the.sunlight.and.felt.warmer?.You.may.think.that.heat.comes.straight.from.the.Sun.to.Earth,.but.it.doesn’t..Sunlight.is.radiant energy..Radiant.energy.comes.in.many.different.forms..When.sunlight.hits.your.skin,.it.changes.to.heat..Your.microwave.oven.uses.another.kind.of.radiant.energy.to.cook.your.food.8

Nature can melt rocks, heat water underground, and make gorgeous displays of heat energy.

Heat.energy.comes.from.natural.sources,.too..Lightning.is.a.natural.source.of.heat.that.makes.air.spread.out.very.fast.(causing.thunder)..And.did.you.know..that.Earth.has.its.own.heat.buried.deep.underground,.called.geothermal heat?.It’s.so.hot.under.Earth’s.crust.that.rocks.melt..Sometimes.the.molten.rock.comes.to.the.surface.as.a.volcano..In.other.places,.the.molten.rock.comes.close.to.the.surface,..but.doesn’t.come.out..This.melted,.underground.rock.can.heat.water.trapped.in.the.ground..The.water.will.come.shooting.out.of.the.ground.as.a.geyser.

Radiant energy from the Sun

Sun’s energy turns to heat

Earth absorbs Sun’s energy

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Here.is.a.rule.about.heat.energy..Heat.energy.always.moves.from.warmer.to.cooler..When.sunlight.hits.the.ground,.it.turns.to.heat..Then.the.heat.moves.from.the.hot.ground.to.the.cooler.air.above.it..This.keeps.the.planet.warm.

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Dark things take in more of the Sun’s energy than light-colored things. That’s why light-colored clothes keep you cooler on a hot summer day. So which would feel warmer in the sun: a white rock or a black rock?

The heat energy of each particle affects how fast it moves.

Temperature

All.matter.(everything.that.has.weight.and.takes.up.space).is.made.of.tiny.particles,.too.small.to.see..These.particles.are.always.moving,.just.a.little,.tiny.bit..Every.object.also.has.heat.energy,.and.how.much.heat.energy.an.object.has.affects.how.quickly.its.particles.move..An.object.with.less.heat.energy.has.particles.

that.move.more.slowly,.and.an.article.with.more.heat.energy.has.particles.that.move.more.quickly.

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We.use.temperature.to.tell.how.much.heat.energy.things.have..The.less.heat.energy.an.object.has,.the.more.slowly..its.particles.move.and.the.colder.its.temperature..The.more.heat.energy.an.object.has,.the.faster.its.particles.move.and.the.hotter.its.temperature..We.use.a.thermometer.to.measure.temperature.

Boiling.water.has.so.much.heat.energy,.it.makes.the.tiny.particles.in.water.move.really.fast!.The.temperature.of.boiling.water.is.100.degrees.Celsius.

Ice,.or.frozen.water,.has.so.little.heat.energy.that.the.tiny.particles.in.it.move.very.slowly..The.temperature.of.frozen.water.is.0.degrees.Celsius.

Thermometer comes from two words. Thermo means “heat.” Meter means “an object used to measure.” So a thermometer is an object used to measure how hot something is.

When particles have more heat, they move faster.

Water freezes at 0° Celsius, and it boils at 100° Celsius. A thermometer can tell you how hot or cold the water is.

13 14

Conduction

Heat.moves.most.easily.through.solids..This.is.because.the.particles.in.solids.are.closer.together.than.the.particles.in.air.or.liquid..Heat.can.quickly.transfer.from.one.particle.to.another.when.they.are.close.together..Heat.moves.through.solids.by.conduction.

Heat Moves Through Things

You.know.that.the.temperature.of.something.can.change..The.water.that.was.boiling.at.100°.Celsius.freezes.solid..if.you.put.it.in.the.freezer.long.enough..And.if.you.leave.an.ice.cube.out.on.a.plate,.it.will.melt..Other.objects.change.temperature,.too..Pizza.that’s.hot.from.the.oven.will.get.cold.over.time..The.pizza.and.water.change.temperature.because.heat.energy.moves.through.them.

Heat.energy.moves.through.solids.(like.pizza),.and.liquids.and.gases.(like.water.and.air)..But.it.moves.differently.through.solids.than.it.moves.through.liquids.and.gases.

Heat moves through particles in pizza.

Solid: Particles are closest together, in a pattern. Heat moves easily through particles.

Liquid: Particles are farther apart than in solids. It takes longer for heat to move through a liquid.

Gas: Particles are farthest apart. Heat moves

slowest in a gas.

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What.happens.to.the.particles.in.this.metal.rod.when.they.touch.fire?.First,.they.get.heat.energy.from.the.fire..The.heat.energy.makes.them.move.fast..The.hotter.particles.bump.into.other,.cooler.particles.in.the.rod..This.makes.the.cooler.particles.heat.up.and.move.faster..The.heat.energy.moves.up.the.rod,.until.all.its.particles.are.hot..In.time,.the.rod.will.be.too.hot.to.hold!

A.good.conductor.is.something.that.heat.can.move.through.easily..Metal.is.a.good.conductor..Pots.and.pans.are.made.of.metal.because.it.helps.

food.cook.fast..

But.wood.and.plastic.are.solids.that.are.not.good.conductors..Heat.energy.moves.slowly.in.these.solids..Solids.that.do.not.conduct.heat.well.are.called.insulators..Pan.handles.are.made.of.wood.and.plastic.because.they.stay.cool. Insulated cups keep heat in,

while oven mitts keep heat out.

A metal pot is a good conductor.

Particles higher up are still cool and slow.

Particles in the fire get hot and move fast.

17 18

Now.the.soup.at.the.top.of.the.pot.is.cooler..It.is.also.heavier,.so.it.sinks!.The.cool.soup.pushes.the.lighter,.hotter.soup.up.to.the.top..Now.the.heavier,.cooler.soup.takes.in.heat.from.the.bottom.of.the.hot.pot..It.will.rise.to.the.top.of.the.pot.and.sink.again..This.is.how.soup.churns.and.boils.and.makes.the.soup.hot!cool soup

soup heats up

fire heats the pan

particles close and slow moving

particles far apart and moving fast

Convection

Let’s.look.at.how.heat.moves.through..a.liquid,.like.soup..A.hot.pot.heats.the.soup.at.the.bottom.first..The.heat.makes.these.soup.particles.move.fast.and.spread.out..When.the.particles.spread.out,.the.soup.gets.lighter!.So.the.soup.at.the.bottom.of.the.pot.is.lighter.than.the.soup.at.the.top.

19 20

Now.let’s.learn.how.heat.moves.through.a.gas,.like.air..When.the.ground.warms.air.above.it,.the.air.rises..The.heavier,.cooler.air.from.above.sinks.and.pushes.the.warmer.air.up..The.warm.air.becomes.cool.as.it.moves.away.from.the.warmer.ground..At.the.same.time,.the.cooler.air.that.sank.toward.the.ground.is.getting.heated..Cooler.air.is.always.sinking.to.push.up.warmer.air..This.rising.and.sinking.air.makes.wind!.The.movement.of.heat.energy.through.liquids.and.gases.is.called.convection.

Heat Energy and You

Your.body.works..to.stay.at.a.temperature.of.98.6ºF.(37ºC)..So.when.you.get.too.hot,.you.sweat..As.sweat.evaporates.from.your.skin,.it.

takes.heat.from.your.body.and.releases..it.to.the.air..Now.your.skin.has.a.lower.temperature.and.your.body.feels.cooler..To.stay.warm,.you.wear.thick.clothes..The.clothes.you.wear.when.it.is.cold.are.a.good.insulator..They.stop.the.heat.from.leaving.your.body.

Clothing keeps you warm.

Sweat keeps your body cool.

Energy from the Sun turns to heat when it is absorbed by the ground. Then heat from the ground warms the air above it. Cooler air from above pushes the air up.

21 22

You.have.learned.that.heat.is.one.of.many.kinds.of.energy..It.is.an.important.form.of.energy.that.we.use.each.day..You.have.also.learned.that.heat.moves.through.solids,.liquids,.and.gases.by.passing.from.particle.to.particle..You.know.it.moves.from.hotter.areas.to.cooler.areas..Temperature.is.how.we.measure.how.hot.or.cold.something.is..

There.are.many.sources.of.heat.energy,.including.fuels,.electricity,.and.natural.sources.like.the.sun,.lightning,.geysers,.and.volcanoes.

Imagine being lost outdoors in the woods on a cold day.

You do not have matches to start a fire. How would you stay warm?

Answers will vary. Possible answers: build a shelter from tree branches and brush, rub sticks together so that friction makes them burn, pile up leaves and grass and crawl under them to stay warm.

Homes.and.buildings.keep.us.cool.on.hot.days.and.warm.on.cold.days..We.use.fuel.to.heat.our.homes..We.put.insulation.in.the.walls.and.ceilings.of.our.homes..In.the.summer,.insulation.helps.keep.out.the.hot.air..In.the.winter,.insulation.helps.keep.in.the.warm.air.

Most of our energy comes from the Sun.

Insulation has lots of tiny air pockets in it. Air is a good insulator.

Glossary

conduction. .the.transfer.of.heat.from.one.object.to.another.(p..14)

conductor. .a.material.that.transfers.heat.from.one.object.to.another.(p..16)

convection. .the.transfer.of.heat.by.movement.in.a.liquid..or.gas.(p..19)

evaporate. ..to.change.from.a.liquid.state.to.a.gas.state.(p..20)

friction. .force.that.builds.up.when.two.objects.rub.against.each.other.(p..5)

fuel. .any.material.used.to.produce.heat.or.power.(p..6)

geothermal heat. .heat.energy.from.inside.the.Earth.in.the.form.of.steam.or.hot.water.that.is.sometimes.used.to.produce.power.(p..7)

geyser. .a.hot.spring.that.boils.from.time.to.time,.sending.a.column.of.water.and.steam.into.the.air.(p..7)

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heat energy. .a.form.of.energy.that.is.transferred.from.an.object.with.a.higher.temperature.to.an.object.with.a.lower.temperature.(p..4)

insulator. .material.that.conducts.heat.poorly.(p..16)

matter. .anything.that.takes.up.space.and.has.weight.(p..10)

radiant energy. .energy.that.travels.in.waves.(p..8)

temperature. .unit.of.measure.telling.how.hot.or.cold.something..is.(p..11)

thermometer. .a.tool.used.for.measuring.temperature.(p..11)

transfer. .to.move.from.one.placeto.another.(p..14)

Index

cooking,.4,.8,.16–18

particles,.10–12,.14–15,.17,.22

sunlight,.8,.9,.22

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