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370 How Are Train Schedules & Oil Pumps Connected? How Are Train Schedules & Oil Pumps Connected? Douglas Peebles/CORBIS

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370

How AreTrain Schedules

& Oil PumpsConnected?

How AreTrain Schedules

& Oil PumpsConnected?

Douglas Peebles/CORBIS

Visit to find project ideas and resources.Projects include:• Career As a class, design a chart of the many fields of engineering and how

they relate to conserving and protecting the environment.• Technology Design and construct miniature models of energy-producing

devices. Explain how your model works.• Model Analyze locations for a future city. Consider what characteristics will

make the best location and make a model of a portion of your design.Mag Lev Trains: Floating Locomotives encourages understandingof magnets and their application in the transportation field.Design a mag lev train and present it to the class.

ips.msscience.com/unit_project

In the 1800s, trains had to make frequent stops so that their moving parts could be lubricated.Without lubrication, the parts would have worn out due to friction. When the train stopped, a

worker had to get out and oil the parts by hand. The process was very time-consuming and madeit hard for trains to stay on schedule. Around 1870, an engineer named Elijah McCoy developedthe first automatic lubricating device, which oiled the engine while the train was running. (Alater version of his automatic lubricator is seen at lower right.) Since then, many kinds of automatic lubricating devices have been developed. Today, automobiles have oil pumps thatautomatically circulate oil to the moving parts of the engine. When you go for a ride in a car, youcan thank Elijah McCoy that you don’t have to stop every few miles to oil the engine by hand!

(inset)Henry Ford Museum & Greenfield Village, (bkgd)Douglas Peebles/CORBIS

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Energy and EnergyResources

Blowing Off SteamThe electrical energy you used today might have been producedby a coal-burning power plant like this one. Energy contained incoal is transformed into heat, and then into electrical energy. Asboiling water heated by the burning coal is cooled, steam risesfrom these cone-shaped cooling towers.

Choose three devices that use electricity, and identify the func-tion of each device.Science Journal

S8P2. Students will be familiar with the forms and transformations of energy. Also covers:S8P3; S8CS1–2, 4–6, 9

Changes occur when energyis transferred from one place to another.

SECTION 1What is energy?Main Idea Energy can have different forms.

SECTION 2Energy TransformationsMain Idea Energy canchange form, but can neverbe created or destroyed.

SECTION 3Sources of EnergyMain Idea Energy contained in differentenergy sources is trans-formed into useful forms of energy.

(bkgd.)Chris Knapton/Science Photo Library/Photo Researchers

655-S1-MSS08 714_IPS_GA.ps 1/11/07 4:52 AM Page 714

Energy Make the followingFoldable to help identify whatyou already know, what you

want to know, and what you learned aboutenergy.

Fold a vertical sheetof paper from side toside. Make the frontedge about 1 cmshorter than the backedge.

Turn lengthwiseand fold into thirds

Unfold, cut, and label each tab foronly the top layer along both folds tomake three tabs.

Identify Questions Before you read the chapter,write what you know and what you want to knowabout the types, sources, and transformation ofenergy under the appropriate tabs. As you readthe chapter, correct what you have written andadd more questions under the Learned tab.

STEP 3

STEP 2

STEP 1

Marbles and EnergyWhat’s the difference between a movingmarble and one at rest? A moving marblecan hit something and cause a change tooccur. How can a marble acquire energy—the ability to cause change?

1. Make a track on atable by slightly sepa-rating two metersticksplaced side by side.

2. Using a book, raiseone end of the trackslightly and measurethe height.

3. Roll a marble down the track. Measure thedistance from its starting point to where ithits the floor. Repeat. Calculate the aver-age of the two measurements.

4. Repeat steps 2 and 3 for three differentheights. Predict what will happen if youuse a heavier marble. Test your predictionand record your observations.

5. Think Critically In your Science Journal,describe how the distance traveled by themarble is related to the height of theramp. How is the motion of the marblerelated to the ramp height?

Start-Up Activities

Preview this chapter’s contentand activities at ips.msscience.com

373373

Know? Learned?Like to know?

(bkgd.)Chris Knapton/Science Photo Library/Photo Researchers, (inset)Matt Meadows

374 A CHAPTER 24 Energy and Energy Resources

Apply It! As you read thischapter, make a chart of the main ideas. Nextto each main idea, list at least two supportingdetails.

Learn It! The best way for you to remember information isto write it down, or take notes. Good note-taking is useful for studying and research. When you are taking notes, it is helpful to• phrase the information in your own words;• restate ideas in short, memorable phrases;• stay focused on main ideas and only the most important supporting

details.

Practice It! Make note-taking easier by using a chart tohelp you organize information clearly. Write the main ideas in the left col-umn. Then write at least three supporting details in the right column. Readthe text from Section 2 of this chapter under the heading Energy ChangesForm, pages 381–383. Then take notes using a chart, such as the one below.

Main Idea Supporting Details

1.2.3.4.5.

1.2.3.4.5.

374 B

Before You Read Statement After You ReadA or D A or D

1 Only objects that are moving have energy.

2 Energy of motion depends only on the object’smass and speed.

3 The amount of thermal energy an object hasdepends on its temperature.

4 Energy changes from one form to another whena ball is thrown upward.

5 Living organisms change chemical energy tothermal energy.

6 The total amount of energy increases when acandle burns.

7 Coal is being made faster than it is being used.

8 Solar energy is the least expensive energysource.

9 A heat pump can heat and cool a building.

Print out a worksheetof this page at ips.msscience.com

Read one or two paragraphs

first and take notes after you

read. You are likely to take

down too much information

if you take notes as you read.Use this to focus on the main ideas as you read the chapter.

Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper.

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

After you read the chapter, look back to this page to see if you’ve

changed your mind about any of the statements.

• If any of your answers changed, explain why.

• Change any false statements into true statements.

• Use your revised statements as a study guide.

The Nature of EnergyWhat comes to mind when you hear the word energy? Do you

picture running, leaping, and spinning like a dancer or a gymnast?How would you define energy? When an object has energy, it canmake things happen. In other words, energy is the ability to causechange. What do the items shown in Figure 1 have in common?

Look around and notice the changes that are occurring—someone walking by or a ray of sunshine that is streaming throughthe window and warming your desk. Maybe you can see the windmoving the leaves on a tree. What changes are occurring?

Transferring Energy You might not realize it, but you have alarge amount of energy. In fact, everything around you hasenergy, but you notice it only when a change takes place.Anytime a change occurs, energy is transferred from one objectto another. You hear a footstep because energy is transferredfrom a foot hitting the ground to your ears. Leaves are put intomotion when energy in the moving wind is transferred to them.The spot on the desktop becomes warmer when energy is trans-ferred to it from the sunlight. In fact, all objects, including leavesand desktops, have energy.

■ Explain what energy is.■ Distinguish between kinetic

energy and potential energy.■ Identify the various forms of

energy.

Energy is involved whenever achange occurs.

Review Vocabularymass: a measure of the amountof matter in an object

New Vocabulary

• energy

• kinetic energy

• potential energy

• thermal energy

• chemical energy

• radiant energy

• electrical energy

• nuclear energy

What is energy?

Figure 1 Energy is the ability to cause change.Explain how these objects cause change.

374 CHAPTER 13 Energy and Energy Resources

S8P2b. Explain the relationship between potential and kinetic energy. S8P2c. Compare and con-trast the different forms of energy (heat, light, electricity, mechanical motion, sound) and theircharacteristics.

(l c)file photo, (r)Mark Burnett

655-S1-MSS08 716_IPS_GA.ps 1/11/07 4:53 AM Page 716

Energy of MotionThings that move can cause change. A bowling ball rolls

down the alley and knocks down some pins, as in Figure 2A. Isenergy involved? A change occurs when the pins fall over. Thebowling ball causes this change, so the bowling ball has energy.The energy in the motion of the bowling ball causes the pins tofall. As the ball moves, it has a form of energy called kineticenergy. Kinetic energy is the energy an object has due to itsmotion. If an object isn’t moving, it doesn’t have kinetic energy.

Kinetic Energy and Speed If you roll thebowling ball so it moves faster, what happenswhen it hits the pins? It might knock downmore pins, or it might cause the pins to go fly-ing farther. A faster ball causes more change tooccur than a ball that is moving slowly. Look atFigure 2B. The professional bowler rolls a fast-moving bowling ball. When her ball hits thepins, pins go flying faster and farther than for aslower-moving ball. All that action signals thather ball has more energy. The faster the ballgoes, the more kinetic energy it has. This is truefor all moving objects. Kinetic energy increasesas an object moves faster.

How does kinetic energydepend on speed?

Kinetic Energy and Mass Suppose, asshown in Figure 2C, you roll a volleyball downthe alley instead of a bowling ball. If the volley-ball travels at the same speed as a bowling ball,do you think it will send pins flying as far? Theanswer is no. The volleyball might not knockdown any pins. Does the volleyball have lessenergy than the bowling ball even though theyare traveling at the same speed?

An important difference between the volley-ball and the bowling ball is that the volleyball hasless mass. Even though the volleyball is movingat the same speed as the bowling ball, the volley-ball has less kinetic energy because it has lessmass. Kinetic energy also depends on the mass ofa moving object. Kinetic energy increases as themass of the object increases.

Figure 2 The kinetic energyof an object depends on the massand speed of the object.

This ballhas more kineticenergy because ithas more speed.

This ballhas less kineticenergy becauseit has less mass.

This ballhas kineticenergy becauseit is rollingdown the alley.

SECTION 1 What is energy? 375(t b)Bob Daemmrich, (c)Al Tielemans/Duomo

376 CHAPTER 13 Energy and Energy Resources

Energy of PositionAn object can have energy even though

it is not moving. For example, a glass ofwater sitting on the kitchen table doesn’thave any kinetic energy because it isn’t mov-ing. If you accidentally nudge the glass andit falls on the floor, changes occur. Gravitypulls the glass downward, and the glass hasenergy of motion as it falls. Where did thisenergy come from?

When the glass was sitting on the table,it had potential (puh TEN chul) energy.Potential energy is the energy stored in anobject because of its position. In this case,the position is the height of the glass abovethe floor. The potential energy of the glasschanges to kinetic energy as the glass falls.The potential energy of the glass is greater ifit is higher above the floor. Potential energy

also depends on mass. The more mass an object has, the morepotential energy it has. Which object in Figure 3 has the mostpotential energy?

Forms of EnergyFood, sunlight, and wind have energy, yet they seem differ-

ent because they contain different forms of energy. Food andsunlight contain forms of energy different from the kineticenergy in the motion of the wind. The warmth you feel fromsunlight is another type of energy that is different from theenergy of motion or position.

Thermal Energy The feeling of warmth from sunlight sig-nals that your body is acquiring more thermal energy. Allobjects have thermal energy that increases as its temperatureincreases. A cup of hot chocolate has more thermal energy than

a cup of cold water, as shown in Figure 4.Similarly, the cup of water has more thermalenergy than a block of ice of the same mass.Your body continually produces thermalenergy. Many chemical reactions that takeplace inside your cells produce thermalenergy. Where does this energy come from?Thermal energy released by chemical reac-tions comes from another form of energycalled chemical energy.

Figure 3 The potentialenergy of an object depends onits mass and height above theground. Determine which vase hasmore potential energy, the redone or the blue one.

Figure 4 The hotter an object is,the more thermal energy it has. Acup of hot chocolate has more ther-mal energy than a cup of cold water,which has more thermal energy thana block of ice with the same mass.

KS Studios

SECTION 1 What is energy? 377

Chemical Energy When you eat a meal, you are putting asource of energy inside your body. Food contains chemicalenergy that your body uses to provide energy for your brain, topower your movements, and to fuel your growth. As in Figure 5,food contains chemicals, such as sugar, which can be brokendown in your body. These chemicals are made of atoms that arebonded together, and energy is stored in the bonds betweenatoms. Chemical energy is the energy stored in chemical bonds.When chemicals are broken apart and new chemicals areformed, some of this energy is released. The flame of a candle isthe result of chemical energy stored in the wax. When the waxburns, chemical energy is transformed into thermal energy andlight energy.

When is chemical energy released?

Light Energy Light from the candle flame travels through theair at an incredibly fast speed of 300,000 km/s. This is fastenough to circle Earth almost eight times in 1 s. When lightstrikes something, it can be absorbed, transmitted, or reflected.When the light is absorbed by an object, the object can becomewarmer. The object absorbs energy from the light and thisenergy is transformed into thermal energy. Then energy carriedby light is called radiant energy. Figure 6 shows a coil of wirethat produces radiant energy when it is heated. To heat themetal, another type of energy can be used—electrical energy.

Figure 5 Complex chemicals in food storechemical energy. During activity, the chemicalenergy transforms into kinetic energy.

Figure 6 Electrical energy istransformed into thermal energy inthe metal heating coil. As themetal becomes hotter, it emitsmore radiant energy.

Sugar

(l r)Bob Daemmrich, (b)Andrew McClenaghan/Science Photo Library/Photo Researchers

378 CHAPTER 13 Energy and Energy Resources

Self Check1. Explain why a high-speed collision between two cars

would cause more damage than a low-speed collisionbetween the same two cars.

2. Describe the energy transformations that occur when apiece of wood is burned.

3. Identify the form of energy that is converted into ther-mal energy by your body.

4. Explain how, if two vases are side by side on a shelf,one could have more potential energy.

5. Think Critically A golf ball and a bowling ball are mov-ing and both have the same kinetic energy. Which one ismoving faster? If they move at the same speed, whichone has more kinetic energy?

SummaryThe Nature of Energy

• Energy is the ability to cause change.

• Kinetic energy is the energy an object hasdue to its motion. Kinetic energy depends onan object’s speed and mass.

• Potential energy is the energy an object hasdue to its position. Potential energy dependson an object’s height and mass.

Forces of Energy

• Thermal energy increases as temperatureincreases.

• Chemical energy is the energy stored in chem-ical bonds in molecules.

• Light energy, also called radiant energy, is theenergy contained in light.

• Electrical energy is the energy carried by elec-tric current.

• Nuclear energy is the energy contained in thenucleus of an atom.

6. Communicate In your Science Journal, record differ-ent ways the word energy is used. Which ways ofusing the word energy are closest to the definition of energy given in this section?

Electrical Energy Electrical lighting isone of the many ways electrical energy is used. Look around at all the devices that useelectricity. Electric current flows in thesedevices when they are connected to batteries orplugged into an electric outlet. Electricalenergy is the energy that is carried by an elec-tric current. An electric device uses the electri-cal energy provided by the current flowing inthe device. Large electric power plants generatethe enormous amounts of electrical energyused each day. About 20 percent of the electri-cal energy used in the United States is gener-ated by nuclear power plants.

Nuclear Energy Nuclear power plants use the energy stored inthe nucleus of an atom to generate electricity. Every atomicnucleus contains energy—nuclear energy—that can be trans-formed into other forms of energy. However, releasing the nuclearenergy is a difficult process. It involves the construction of com-plex power plants, shown in Figure 7. In contrast, all that isneeded to release chemical energy from wood is a lighted match.

Figure 7 Complex power plantsare required to obtain useful energyfrom the nucleus of an atom.

ips.msscience.com/self_check_quizMark Burnett/Photo Researchers

Changing Forms of EnergyChemical, thermal, radiant, and electrical are some of the

forms that energy can have. In the world around you, energy istransforming continually between one form and another. Youobserve some of these transformations by noticing a change inyour environment. Forest fires are a dramatic example of anenvironmental change that can occur naturally as a result oflightning strikes. A number of changes occur that involve energyas the mountain biker in Figure 8 pedals up a hill. What energytransformations cause these changes to occur?

Tracking Energy Transformations As the mountain bikerpedals, his leg muscles transform chemical energy into kineticenergy. The kinetic energy of his leg muscles transforms intokinetic energy of the bicycle as he pedals. Some of this energytransforms into potential energy as he moves up the hill. Also,some energy is transformed into thermal energy. His body iswarmer because chemical energy is being released. Because offriction, the mechanical parts of the bicycle are warmer, too.Thermal energy is almost always produced by an energy trans-formation. The energy transformations that occur when peopleexercise, when cars run, when living things grow and even whenstars explode, all produce thermal energy.

Energy Transformations

■ Apply the law of conservation ofenergy to energy transformations.

■ Identify how energy changesform.

■ Describe how electric powerplants produce energy.

Changing energy from one form toanother is what makes cars run, fur-naces heat, telephones work, andplants grow.

Review Vocabularytransformation: a change incomposition or structure

New Vocabulary

• law of conservation of energy

• generator

• turbine

379

Figure 8 The ability to transform energyallows the biker to climb the hill. Identify all the forms of energy that arerepresented in the photograph.

S8P2a. Explain energy transformation in terms of the Law of Conservation of Energy. S8P2b.Explain the relationship between potential and kinetic energy.

Lori Adamski Peek/Stone/Getty Images

655-S2-MSS08 721_IPS_GA.ps 1/12/07 12:34 AM Page 721

The Law of Conservation of Energy It can be a challenge to track energy as it moves from object

to object. However, one extremely important principle can serveas a guide as you trace the flow of energy. According to the law of conservation of energy, energy is never created ordestroyed. The only thing that changes is the form in whichenergy appears. When the biker is resting at the summit, all hisoriginal energy is still around. Some of the energy is in the formof potential energy, which he will use as he coasts down the hill.Some of this energy was changed to thermal energy by frictionin the bike. Chemical energy was also changed to thermal energyin the biker’s muscles, making him feel hot. As he rests, this ther-mal energy moves from his body to the air around him. Noenergy is missing—it can all be accounted for.

Can energy ever be lost? Why or why not?

Changing Kinetic and Potential EnergyThe law of conservation of energy can be used to identify the

energy changes in a system. For example, tossing a ball into theair and catching it is a simple system. As shown in Figure 9, asthe ball leaves your hand, most of its energy is kinetic. As the ballrises, it slows and its kinetic energy decreases. But, the totalenergy of the ball hasn’t changed. The decrease in kinetic energyequals the increase in potential energy as the ball flies higher inthe air. The total amount of energy remains constant. Energymoves from place to place and changes form, but it never is cre-ated or destroyed.

Figure 9 During the flight of thebaseball, energy is transformingbetween kinetic and potentialenergy.Determine where the ball has themost kinetic energy. Where does theball have the most total energy?

Topic: EnergyTransformationsVisit for Weblinks to information about energytransformations that occur duringdifferent activities and processes.

Activity Choose an activity orprocess and make a graph showinghow the kinetic and potentialenergy change during it.

ips.msscience.com

380 CHAPTER 13

Potentialenergy

Kineticenergy

Kineticenergy

Richard Hutchings

Analyzing EnergyTransformationsProcedure1. Place soft clay on the floor

and smooth out its surface.2. Hold a marble 1.5 m

above the clay and drop it.Measure the depth of thecrater made by the marble.

3. Repeat this procedureusing a golf ball and aplastic golf ball.

Analysis1. Compare the depths of the

craters to determine whichball had the most kineticenergy as it hit the clay.

2. Explain how potentialenergy was transformedinto kinetic energy duringyour activity.

Energy Changes FormEnergy transformations occur constantly all around you.

Many machines are devices that transform energy from oneform to another. For example, an automobile engine trans-forms the chemical energy in gasoline into energy of motion.However, not all of the chemical energy is converted intokinetic energy. Instead, some of the chemical energy is con-verted into thermal energy, and the engine becomes hot. Anengine that converts chemical energy into more kinetic energyis a more efficient engine. New types of cars, like the one shownin Figure 10, use an electric motor along with a gasolineengine. These engines are more efficient so the car can travelfarther on a gallon of gas.

Transforming Chemical EnergyInside your body, chemical energy also is

transformed into kinetic energy. Look at Figure 11. The trans-formation of chemical to kinetic energy occurs in muscle cells.There, chemical reactions take place that cause certain mole-cules to change shape. Your muscle contracts when many ofthese changes occur, and a part of your body moves.

The matter contained in living organisms, also called bio-mass, contains chemical energy. When organisms die, chemicalcompounds in their biomass break down. Bacteria, fungi, andother organisms help convert these chemical compounds tosimpler chemicals that can be used by other living things.

Thermal energy also is released as these changes occur. Forexample, a compost pile can contain plant matter, such as grassclippings and leaves. As the compost pile decomposes, chemicalenergy is converted into thermal energy. This can cause the tem-perature of a compost pile to reach 60°C.

Figure 10 Hybrid cars that use an electric motor anda gasoline engine for power are now available. Hybridcars make energy transformations more efficient.

Gasolineengine

Electricmotor

Battery

Generator

SECTION 2 Energy Transformations 381Ron Kimball/Ron Kimball Photography

Figure 11

VISUALIZING ENERGY TRANSFORMATIONS

Paddling a raft, throwinga baseball, playing theviolin — your skeletal

muscles make these andcountless other body move-ments possible. Muscles workby pulling, or contracting. Atthe cellular level, muscle con-tractions are powered by reac-tions that transform chemicalenergy into kinetic energy.

Energy transforma-tions taking place inyour muscles providethe power to move.

Many skeletal muscles are arranged in pairs that work in opposition to eachother. When you bend your arm, thebiceps muscle contracts, while the tricepsrelaxes. When you extend your arm thetriceps contracts, and the biceps relaxes.

Biceps

Triceps

Muscle fibers

Skeletal muscles are made up of bundles of muscle cells, orfibers. Each fiber is composed ofmany bundles of muscle filaments.

▼ A signal from a nerve fiber starts achemical reaction in the muscle filament.This causes molecules in the muscle fila-ment to gain energy and move. Many filaments moving together cause themuscle to contract.

Skeletal muscle

Muscle fiber

Bundle of musclefibers

Filamentbundle

Muscle filaments

Nerve fiber

382 CHAPTER 13

(t)Judy Lutz, (b)Lennart Nilsson

Transforming Electrical Energy Every day you use electri-cal energy. When you flip a light switch, or turn on a radio or tel-evision, or use a hair drier, you are transforming electricalenergy to other forms of energy. Every time you plug somethinginto a wall outlet, or use a battery, you are using electricalenergy. Figure 12 shows how electrical energy is transformedinto other forms of energy when you listen to a radio. A loud-speaker in the radio converts electrical energy into sound wavesthat travel to your ear—energy in motion. The energy that iscarried by the sound waves causes parts of the ear to move also.This energy of motion is transformed again into chemical andelectrical energy in nerve cells, which send the energy to yourbrain. After your brain interprets this energy as a voice or music,where does the energy go? The energy finally is transformed intothermal energy.

Transforming Thermal Energy Different forms of energycan be transformed into thermal energy. For example, chemicalenergy changes into thermal energy when something burns.Electrical energy changes into thermal energy when a wire thatis carrying an electric current gets hot. Thermal energy can beused to heat buildings and keep you warm. Thermal energy alsocan be used to heat water. If water is heated to its boiling point,it changes to steam. This steam can be used to produce kineticenergy by steam engines, like the steam locomotives that used topull trains. Thermal energy also can be transformed into radiantenergy. For example, when a bar of metal is heated to a hightemperature, it glows and gives off light.

Figure 12 The simple act of listening to a radio involvesmany energy transformations. A few are diagrammed here.

Electrical energy of brain and nerve cells

Kinetic energy of eardrum

and fluid

Soundenergyof air

Kineticenergy

of speaker

Electrical energy of

radio signal

Controlling BodyTemperature Mostorganisms have someadaptation for controllingthe amount of thermalenergy in their bodies.Some living in cooler cli-mates have thick furcoats that help preventthermal energy fromescaping, and some liv-ing in desert regionshave skin that helps keepthermal energy out.Research some of theadaptations differentorganisms have for con-trolling the thermalenergy in their bodies.

SECTION 2 Energy Transformations 383

384 CHAPTER 13 Energy and Energy Resources

How Thermal Energy Moves Thermal energycan move from one place to another. Look atFigure 13. The hot chocolate has thermal energythat moves from the cup to the cooler air aroundit, and to the cooler spoon. Thermal energy onlymoves from something at a higher temperature tosomething at a lower temperature.

Generating Electrical Energy The enormous amount of electrical energy

that is used every day is too large to be stored inbatteries. The electrical energy that is available foruse at any wall socket must be generated continu-ally by power plants. Every power plant works onthe same principle—energy is used to turn a large

generator. A generator is a device that transforms kinetic energyinto electrical energy. In fossil fuel power plants, coal, oil, or nat-ural gas is burned to boil water. As the hot water boils, the steamrushes through a turbine, which contains a set of narrowlyspaced fan blades. The steam pushes on the blades and turns theturbine, which in turn rotates a shaft in the generator to producethe electrical energy, as shown in Figure 14.

What does a generator do?

Figure 13 Thermal energymoves from the hot chocolateto the cooler surroundings.Explain what happens to the hotchocolate as it loses thermal energy.

Conveyorbelt

Coal supply

Stack Steam line Turbine Generator

Chemical energyin coal

Thermal energyin water

Kinetic energyof steam

Kinetic energyof turbine

Electrical energyout of generator

Transformerthat increases

voltage

Boiler

Cooling water

River or reservoir

Figure 14 A coal-burning powerplant transforms the chemicalenergy in coal into electrical energy.List some of the other energysources that power plants use.

KS Studios

Self Check1. Describe the conversions between potential and

kinetic energy that occur when you shoot a basketballat a basket.

2. Explain whether your body gains or loses thermalenergy if your body temperature is 37°C and thetemperature around you is 25°C.

3. Describe a process that converts chemical energy tothermal energy.

4. Think Critically A lightbulb converts 10 percent ofthe electrical energy it uses into radiant energy.Make a hypothesis about the other form of energyproduced.

SummaryChanging Forms of Energy

• Heat usually is one of the forms of energy pro-duced in energy transformations.

• The law of conservation of energy states thatenergy cannot be created or destroyed; it canonly change form.

• The total energy doesn’t change when anenergy transformation occurs.

• As an object rises and falls, kinetic and poten-tial energy are transformed into each other,but the total energy doesn’t change.

Generating Electrical Energy

• A generator converts kinetic energy into elec-trical energy.

• Burning fossil fuels produces thermal energythat is used to boil water and produce steam.

• In a power plant, steam is used to spin a tur-bine which then spins an electric generator.

5. Use a Ratio How many times greater is the amount ofelectrical energy produced in the United States bycoal-burning power plants than the amount produced by nuclear power plants?

Power Plants Almost 90 percent of the electricalenergy generated in the United States is produced bynuclear and fossil fuel power plants, as shown inFigure 15. Other types of power plants include hydro-electric (hi droh ih LEK trihk) and wind. Hydroelec-tric power plants transform the kinetic energy ofmoving water into electrical energy. Wind powerplants transform the kinetic energy of moving air intoelectrical energy. In these power plants, a generatorconverts the kinetic energy of moving water or windto electrical energy.

To analyze the energy transformations in a powerplant, you can diagram the energy changes using arrows. A coal-burning power plant generates electrical energy through the fol-lowing series of energy transformations.

chemical thermal kinetic kinetic electrical energy → energy → energy → energy → energyof coal of water of steam of turbine out of

generator

Nuclear power plants use a similar series of transformations.Hydroelectric plants, however, skip the steps that change waterinto steam because the water strikes the turbine directly.

Figure 15 The graph showssources of electrical energy in theUnited States.Name the energy source that youthink is being used to provide theelectricity for the lights overhead.

SECTION 2 Energy Transformations 385

Coal51%

Oil3%

Otherrenewable3%

Nuclear20%

Gas14%

Hydro9%

ips.msscience.com/self_check_quiz

You probably have listened to music usingspeakers or headphones. Have you ever consid-ered how energy is transferred to get theenergy from the radio or CD player to yourbrain? What type of energy is needed to powerthe radio or CD player? Where does this energycome from? How does that energy becomesound? How does the sound get to you? In thisactivity, the sound from a radio or CD player isgoing to travel through a motor before enteringyour body through your jaw instead of yourears.

Real-World QuestionHow can energy be transferred from a radio or CD player to your brain?

Goals ■ Identify energy transfers and

transformations.■ Explain your observations using the law of

conservation of energy.

Materialsradio or CD playersmall electrical motorheadphone jack

Procedure1. Go to one of the places in the room with a

motor/radio assembly.

2. Turn on the radio or CD player so that youhear the music.

3. Push the headphone jack into the head-phone plug on the radio or CD player.

4. Press the axle of the motor against the sideof your jaw.

Conclude and Apply1. Describe what you heard in your Science

Journal.

2. Identify the form of energy produced bythe radio or CD player.

3. Draw a diagram to show all of the energytransformations taking place.

4. Evaluate Did anything get hotter as aresult of this activity? Explain.

5. Explain your observations using the law ofconservation of energy.

Hearing with Your Jaw

Compare your conclusions with those ofother students in your class. For more help,refer to the Science Skill Handbook.

386 CHAPTER 13 Energy and Energy Resources

S8P2a. Explain energy transformation in terms of the Law of Conservation of Energy.S8P2c. Compare and contrast the different forms of energy (heat, light, electricity,mechanical motion, sound) and their characteristics. Also covers: S8CS4c, 7d, 9a–b, 9d

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655-S2-MSS08 54_IPS_GA.ps 1/11/07 5:00 AM Page 54

Thermal energy fromradioactive atoms

Radiant energy from the Sun

Surface ofEarth

Using EnergyEvery day, energy is used to provide light and to heat and

cool homes, schools, and workplaces. According to the law ofconservation of energy, energy can’t be created or destroyed.Energy only can change form. If a car or refrigerator can’t createthe energy they use, then where does this energy come from?

Energy ResourcesEnergy cannot be made, but must come from the natural

world. As you can see in Figure 16, the surface of Earthreceives energy from two sources—the Sun and radioactiveatoms in Earth’s interior. The amount of energy Earth receivesfrom the Sun is far greater than the amount generated inEarth’s interior. Nearly all the energy you used today can betraced to the Sun, even the gasoline used to power the car orschool bus you came to school in.

Sources of Energy

■ Explain what renewable, non-renewable, and alternativeresources are.

■ Describe the advantages anddisadvantages of using variousenergy sources.

Energy is vital for survival and mak-ing life comfortable. Developingnew energy sources will improvemodern standards of living.

Review Vocabularyresource: a natural feature orphenomenon that enhances thequality of life

New Vocabulary

• nonrenewable resource

• renewable resource

• alternative resource

• inexhaustible resource

• photovoltaic

SECTION 3 Sources of Energy 387

Figure 16 All the energy youuse can be traced to one of twosources—the Sun or radioactiveatoms in Earth’s interior.

S8P2a. Explain energy transformation in terms of the Law of Conservation of Energy. S8CS6c.Organize scientific information in appropriate tables, charts, and graphs, and identify relationshipsthey reveal. Also covers: S8CS2a–b

655-S3-MSS08 55_IPS_GA.ps 1/11/07 5:18 AM Page 55

388 CHAPTER 13 Energy and Energy Resources

Fossil FuelsFossil fuels are coal, oil, and natural gas. Oil and natural gas

were made from the remains of microscopic organisms thatlived in Earth’s oceans millions of years ago. Heat and pressuregradually turned these ancient organisms into oil and naturalgas. Coal was formed by a similar process from the remains ofancient plants that once lived on land, as shown in Figure 17.

Through the process of photosynthesis, ancient plants con-verted the radiant energy in sunlight to chemical energy storedin various types of molecules. Heat and pressure changed thesemolecules into other types of molecules as fossil fuels formed.Chemical energy stored in these molecules is released when fos-sil fuels are burned.

Using Fossil Fuels The energy used when you ride in a car,turn on a light, or use an electric appliance usually comes fromburning fossil fuels. However, it takes millions of years to replaceeach drop of gasoline and each lump of coal that is burned. Thismeans that the supply of oil on Earth will continue to decreaseas oil is used. An energy source that is used up much faster thanit can be replaced is a nonrenewable resource. Fossil fuels arenonrenewable resources.

Burning fossil fuels to produce energy also generates chemi-cal compounds that cause pollution. Each year billions of kilo-grams of air pollutants are produced by burning fossil fuels.These pollutants can cause respiratory illnesses and acid rain.Also, the carbon dioxide gas formed when fossil fuels are burnedmight cause Earth’s climate to warm.

Figure 17 Coal is formed afterthe molecules in ancient plants areheated under pressure for millionsof years. The energy stored by themolecules in coal originally camefrom the Sun.

TimeHeat

Pressure

Radiant energy Radiant energy from the Sun isstored as chemical energy in molecules.

Coal mine

Energy Source OriginsThe kinds of fossil fuelsfound in the grounddepend on the kinds oforganisms (animal or plant)that died and were buriedin that spot. Research coal,oil, and natural gas to findout what types of organ-isms were primarily respon-sible for producing each.

1. Nuclear energyof atoms

2. Thermal energyof water

3. Kinetic energyof steam

4. Kinetic energyof turbine

Generator

5. Electrical energy out of generator

SECTION 3 Sources of Energy 389

Nuclear EnergyCan you imagine running an automobile on 1 kg of fuel that

releases almost 3 million times more energy than 1 L of gas? Whatcould supply so much energy from so little mass? The answer isthe nuclei of uranium atoms. Some of these nuclei are unstableand break apart, releasing enormous amounts of energy in theprocess. This energy can be used to generate electricity by heatingwater to produce steam that spins an electric generator, as shownin Figure 18. Because no fossil fuels are burned, generating elec-tricity using nuclear energy helps make the supply of fossil fuelslast longer. Also, unlike fossil fuel power plants, nuclear powerplants produce almost no air pollution. In one year, a typicalnuclear power plant generates enough energy to supply 600,000homes with power and produces only 1 m3 of waste.

Nuclear Wastes Like all energy sources, nuclear energy hasits advantages and disadvantages. One disadvantage is theamount of uranium in Earth’s crust is nonrenewable. Another isthat the waste produced by nuclear power plants is radioactiveand can be dangerous to living things. Some of the materials inthe nuclear waste will remain radioactive for many thousands ofyears. As a result the waste must be stored so no radioactivity isreleased into the environment for a long time. One method is toseal the waste in a ceramic material, place the ceramic in protec-tive containers, and then bury the containers far underground.However, the burial site would have to be chosen carefully sounderground water supplies aren’t contaminated. Also, the sitewould have to be safe from earthquakes and other natural disas-ters that might cause radioactive material to be released.

Figure 18 To obtain electricalenergy from nuclear energy, aseries of energy transformationsmust occur.

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390 CHAPTER 13 Energy and Energy Resources

HydroelectricityCurrently, transforming the potential energy of water that is

trapped behind dams supplies the world with almost 20 percentof its electrical energy. Hydroelectricity is the largest renewablesource of energy. A renewable resource is an energy source thatis replenished continually. As long as enough rain and snow fallto keep rivers flowing, hydroelectric power plants can generateelectrical energy, as shown in Figure 19.

Although production of hydroelectricity is largely pollutionfree, it has one major problem. It disrupts the life cycle ofaquatic animals, especially fish. This is particularly true in theNorthwest where salmon spawn and run. Because salmonreturn to the spot where they were hatched to lay their eggs, thedevelopment of dams has hindered a large fraction of salmonfrom reproducing. This has greatly reduced the salmon popula-tion. Efforts to correct the problem have resulted in plans toremove a number of dams. In an attempt to help fish bypasssome dams, fish ladders are being installed. Like most energysources, hydroelectricity has advantages and disadvantages.

Topic: HydroelectricityVisit forWeb links to information about theuse of hydroelectricity in variousparts of the world.

Activity On a map of the world,show where the use of hydroelec-tricity is the greatest.

ips.msscience.com

Is energy consumption outpacing production?

You use energy everyday—to get to school,

to watch TV, and to heator cool your home. Theamount of energy con-sumed by an average per-son has increased overtime. Consequently,more energy must beproduced.

U.S. Energy Overview, 1949–1999

30

60

0

90

120

Year

Ener

gy

(qu

adri

llion

Btu

)

1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999

Produced inthe United States

Consumed inthe United States

Energy imports

Identifying the Problem The graph above shows the energy pro-

duced and consumed in the United Statesfrom 1949 to 1999. How does energy that isconsumed by Americans compare withenergy that is produced in the United States?

Solving the Problem 1. Determine the approximate amount of

energy produced in 1949 and in 1999

and how much it has increased in50 years. Has it doubled or tripled?

2. Do the same for consumption. Has itdoubled or tripled?

3. Using your answers for steps 1 and 2 andthe graph, where does the additionalenergy that is needed come from? Givesome examples.

SECTION 3 Sources of Energy 391

Alternative Sources of EnergyElectrical energy can be generated in several ways. However,

each has disadvantages that can affect the environment and thequality of life for humans. Research is being done to develop newsources of energy that are safer and cause less harm to the envi-ronment. These sources often are called alternative resources.These alternative resources include solar energy, wind, and geo-thermal energy.

Solar EnergyThe Sun is the origin of almost all the energy that is used on

Earth. Because the Sun will go on producing an enormousamount of energy for billions of years, the Sun is an inex-haustible source of energy. An inexhaustible resource is anenergy source that can’t be used up by humans.

Each day, on average, the amount of solar energy that strikesthe United States is more than the total amount of energy usedby the entire country in a year. However, less than 0.1 percent ofthe energy used in the United States comes directly from theSun. One reason is that solar energy is more expensive to usethan fossil fuels. However, as the supply of fossil fuels decreases,the cost of finding and mining these fuels might increase. Then,it may be cheaper to use solar energy or other energy sources togenerate electricity and heat buildings than to use fossil fuels.

What is an inexhaustible energy source?

1. Potential energyof water

2. Kinetic energyof water

3. Kinetic energyof turbine

4. Electrical energyout of generator

Long-distancepower lines

Figure 19 The potential energy of water behinda dam supplies the energy to turn the turbine.Explain why hydroelectric power is a renewableenergy source.

Building a SolarCollectorProcedure1. Line a large pot with black

plastic and fill with water.2. Stretch clear-plastic wrap

over the pot and tape ittaut.

3. Make a slit in the top andslide a thermometer or acomputer probe into thewater.

4. Place your solar collector indirect sunlight and monitorthe temperature changeevery 3 min for 15 min.

5. Repeat your experimentwithout using any blackplastic.

Analysis1. Graph the temperature

changes in both setups. 2. Explain how your solar

collector works.

392 CHAPTER 13 Energy and Energy Resources

Collecting the Sun’s Energy Two types of collectors cap-ture the Sun’s rays. If you look around your neighborhood, youmight see large, rectangular panels attached to the roofs ofbuildings or houses. If, as in Figure 20, pipes come out of thepanel, it is a thermal collector. Using a black surface, a thermalcollector heats water by directly absorbing the Sun’s radiantenergy. Water circulating in this system can be heated to about 70°C. The hot water can be pumped through the house toprovide heat. Also, the hot water can be used for washing andbathing. If the panel has no pipes, it is a photovoltaic (foh toh vol TAY ihk) collector, like the one pictured in Figure 20. A photovoltaic is a device that transforms radiantenergy directly into electrical energy. Photovoltaics are used topower calculators and satellites, including the InternationalSpace Station.

What does a photovoltaic do?

Geothermal EnergyImagine you could take a journey to the center of

Earth—down to about 6,400 km below the surface. Asyou went deeper and deeper, you would find the temper-ature increasing. In fact, after going only about 3 km, thetemperature could have increased enough to boil water.At a depth of 100 km, the temperature could be over900°C. The heat generated inside Earth is called geother-mal energy. Some of this heat is produced when unstableradioactive atoms inside Earth decay, converting nuclearenergy to thermal energy.

At some places deep within Earth the temperature ishot enough to melt rock. This molten rock, or magma,can rise up close to the surface through cracks in thecrust. During a volcanic eruption, magma reaches thesurface. In other places, magma gets close to the surfaceand heats the rock around it.

Geothermal Reservoirs In some regions wheremagma is close to the surface, rainwater and water frommelted snow can seep down to the hot rock throughcracks and other openings in Earth’s surface. The waterthen becomes hot and sometimes can form steam. Thehot water and steam can be trapped under high pressurein cracks and pockets called geothermal reservoirs. Insome places, the hot water and steam are close enough tothe surface to form hot springs and geysers.

Figure 20 Solar energy can becollected and utilized by individu-als using thermal collectors orphotovoltaic collectors.

(t)Dr. Jeremy Burgess/Science Photo Library/Photo Researchers, (b)John Keating/Photo Researchers

Cooling towers

Generator

Electric current

Turbine

Fractures in rock

Hot water

Pump

Cool waterHot water from a geothermal reservoir forces its way through a pipe to the surface where it turns to steam.

The steam turns a turbine that is connected to an electric generator.

The steam is cooled in the cooling towers and condenses into water.

The water is pumped back down into the geothermalreservoir.

SECTION 3 Sources of Energy 393

Geothermal Power Plants In places where the geothermalreservoirs are less than several kilometers deep, wells can bedrilled to reach them. The hot water and steam produced bygeothermal energy then can be used by geothermal powerplants, like the one in Figure 21, to generate electricity.

Most geothermal reservoirs contain hot water under highpressure. Figure 22 shows how these reservoirs can be used togenerate electricity. While geothermal power is an inexhaustiblesource of energy, geothermal power plants can be built only inregions where geothermal reservoirs are close to the surface,such as in the western United States.

Heat Pumps Geothermal heat helps keep the temperature ofthe ground at a depth of several meters at a nearly constant tem-perature of about 10° to 20°C. This constant temperature can beused to cool and heat buildings by using a heat pump.

A heat pump contains a water-filled loop of pipe that isburied to a depth where the temperature is nearly constant. Insummer the air is warmer than this underground temperature.Warm water from the building is pumped through the pipedown into the ground. The water cools and then is pumpedback to the house where it absorbs more heat, and the cycle isrepeated. During the winter, the air is cooler than the groundbelow. Then, cool water absorbs heat from the ground andreleases it into the house.

Figure 21 This geothermalpower plant in Nevada producesenough electricity to power about50,000 homes.

Figure 22 The hot water in ageothermal reservoir is used togenerate electricity in a geother-mal power plant.

Geothermal Education Office

394 CHAPTER 13 Energy and Energy Resources

Energy from the OceansThe ocean is in constant motion. If you’ve been to

the seashore you’ve seen waves roll in. You may haveseen the level of the ocean rise and fall over a period ofabout a half day. This rise and fall in the ocean level iscalled a tide. The constant movement of the ocean is aninexhaustible source of mechanical energy that can beconverted into electric energy. While methods are stillbeing developed to convert the motion in ocean wavesto electric energy, several electric power plants usingtidal motion have been built.

Using Tidal Energy A high tide and a low tide each occurabout twice a day. In most places the level of the ocean changes byless than a few meters. However, in some places the change is muchgreater. In the Bay of Fundy in Eastern Canada, the ocean levelchanges by 16 m between high tide and low tide. Almost 14 trillionkg of water move into or out of the bay between high and low tide.

Figure 23 shows an electric power plant that has been builtalong the Bay of Fundy. This power plant generates enough elec-tric energy to power about 12,000 homes. The power plant is constructed so that as the tide rises, water flows through a turbine that causes an electric generator to spin, as shown in Figure 24A. The water is then trapped behind a dam. When thetide goes out, the trapped water behind the dam is releasedthrough the turbine to generate more electricity, as shown inFigure 24B. Each day electric power is generated for about tenhours when the tide is rising and falling.

While tidal energy is a nonpolluting, inexhaustible energysource, its use is limited. Only in a few places is the differencebetween high and low tide large enough to enable a large elec-tric power plant to be built.

Figure 24 A tidal power plantcan generate electricity when thetide is coming in and going out.

Ocean

Turbine Turbine

Ocean

Figure 23 This tidal powerplant in Annapolis Royal, NovaScotia, is the only operating tidalpower plant in North America.

As the tide comes in, it turns a turbine con-nected to a generator. When high tide occurs,gates are closed that trap water behind a dam.

As the tide goes out and the ocean level drops,the gates are opened and water from behind the damflows through the turbine, causing it to spin and turna generator.

Carsand-Mosher

Self Check1. Diagram the energy conversions that occur when coal is

formed, and then burned to produce thermal energy.

2. Explain why solar energy is considered an inexhaustiblesource of energy.

3. Explain how a heat pump is used to both heat and coola building.

4. Think Critically Identify advantages and disadvantagesof using fossil fuels, hydroelectricity, and solar energyas energy sources.

SummaryNonrenewable Resources

• All energy resources have advantages and dis-advantages.

• Nonrenewable energy resources are usedfaster than they are replaced.

• Fossil fuels include oil, coal, and natural gasand are nonrenewable resources. Nuclearenergy is a nonrenewable resource.

Renewable and Alternative Resources

• Renewable energy resources, such as hydro-electricity, are resources that are replenishedcontinually.

• Alternative energy sources include solarenergy, wind energy, and geothermal energy.

5. Use a Ratio Earth’s temperature increases with depth.Suppose the temperature increase inside Earth is 500°Cat a depth of 50 km. What is the temperature increase at a depth of 10 km?

WindWind is another inexhaustible supply of energy. Modern

windmills, like the ones in Figure 25, convert the kinetic energyof the wind to electrical energy. The propeller is connected to agenerator so that electrical energy is generated when wind spinsthe propeller. These windmills produce almost no pollution.Some disadvantages are that windmills produce noise and thatlarge areas of land are needed. Also, studies have shown thatbirds sometimes are killed by windmills.

Conserving EnergyFossil fuels are a valuable resource. Not only are they burned

to provide energy, but oil and coal also are used to make plasticsand other materials. One way to make the supply of fossil fuelslast longer is to use less energy. Reducing the use of energy iscalled conserving energy.

You can conserve energy and also save money by turning offlights and appliances such as televisions when you are not usingthem. Also keep doors and windows closed tightly when it’s coldor hot to keep heat from leaking out of or into your house.Energy could also be conserved if buildings are properly insu-lated, especially around windows. The use of oil could bereduced if cars were used less and made more efficient, so theywent farther on a liter of gas. Recycling materials such as alu-minum cans and glass also helps conserve energy.

Figure 25 Windmills workon the same basic principles as apower plant. Instead of steam turn-ing a turbine, wind turns the rotors.Describe some of the advantagesand disadvantages of usingwindmills.

SECTION 3 Sources of Energy 395ips.msscience.com/self_check_quizBilly Hustace/Stone/Getty Images

Use the InternetUse the Internet

396 CHAPTER 13 Energy and Energy Resources

Real-World QuestionOver the past 100 years, the amount ofenergy used in the United States and else-where has greatly increased. Today, a num-ber of energy sources are available, such ascoal, oil, natural gas, nuclear energy, hydro-electric power, wind, and solar energy.Some of these energy sources are being usedup and are nonrenewable, but others arereplaced as fast as they are used and, there-fore, are renewable. Some energy sourcesare so vast that human usage has almost noeffect on the amount available. Theseenergy sources are inexhaustible.

Think about the types of energy you useat home and school every day. In this lab,you will investigate how and where energyis produced, and how it gets to you. You will also investigate alterna-tive ways energy can be produced, and whether these sources arerenewable, nonrenewable, or inexhaustible. What are the sources ofthe energy you use every day?

Goals■ Identify how energy

you use is producedand delivered.

■ Investigate alterna-tive sources for theenergy you use.

■ Outline a plan forhow these alternativesources of energy couldbe used.

Data Source

Visit internet_lab for moreinformation about sourcesof energy and for data col-lected by other students.

ips.msscience.com/

Energy to PKwerYour Life

Local Energy Information

Energy Type

Where is that energy produced?

How is that energy produced?

How is that energy delivered to you?

Is the energy source renewable,nonrenewable, or inexhaustible?

What type of alternative energysource could you use instead?

S8P2c. Compare and contrast the different forms of energy (heat, light, electricity,mechanical motion, sound) and their characteristics. S8P3c. Demonstrate the effect ofsimple machines (levers, inclined plane, pulley, wedge, screw, and wheel and axle) onwork. Also covers: S8CS1a, 4a, 4c, 5a, 6a–c, 9a–b, 9d–f

SuperStock

Do not writein this book.

655-S3-MSS08 738_IPS_GA.ps 1/23/07 2:00 AM Page 738

Make a Plan1. Think about the activities you do every day and the things you use. When you

watch television, listen to the radio, ride in a car, use a hair drier, or turn on theair conditioning, you use energy. Select one activity or appliance that uses energy.

2. Identify the type of energy that is used.

3. Investigate how that energy is produced and delivered to you.

4. Determine if the energy source is renewable, nonrenewable, or inexhaustible.

5. If your energy source is nonrenewable, describe how the energy you use couldbe produced by renewable sources.

Follow Your Plan1. Make sure your teacher approves your plan before you start.

2. Organize your findings in a data table, similar to the one that is shown.

Analyze Your Data1. Describe the process for producing and delivering the energy source you

researched. How is it created, and how does it get to you?

2. How much energy is produced by the energy source you investigated?

3. Is the energy source you researched renewable, nonrenewable, or inex-haustible? Why?

Conclude and Apply1. Describe If the energy source you investigated is nonrenewable, how can the use

of this energy source be reduced?

2. Organize What alternative sources of energycould you use for everyday energy needs? Onthe computer, create a plan for using renew-able or inexhaustible sources.

LAB 397

Find this lab using the link below. Postyour data in the table that is provided.Compare your data to those of otherstudents. Combine your data with thoseof other students and make inferencesusing the combined data.

ips.msscience.com/internet_lab

Roger Ressmeyer/CORBIS

Write About ItWhere would you place solar collectors in the United States? Why? For more

information on solar energy, go to ips.msscience.com/science_stats.

... The energy released by theaverage hurricane is equal to about200 times the total energy produced by allof the world’s power plants. Almost all ofthis energy is released as heat whenraindrops form.

Energy to BurnDid you know...

... The energy Earth gets each halfhour from the Sun is enough to meetthe world’s demands for a year. Renewableand inexhaustible resources, including theSun, account for only 18 percent of theenergy that is used worldwide.

... The Calories in one mediumapple will give you enough energy to walkfor about 15 min, swim for about 10 min, orjog for about 9 min.

If walking for 15 minrequires 80 Calories of fuel (from food), how many Calorieswould someone need to consume to walk for 1 h?

398 CHAPTER 13 Energy and Energy Resources(tl)Reuters NewMedia, Inc./CORBI, (tr)PhotoDisc, (br)Dominic Oldershaw

Copy and complete the concept map using the following terms: fossil fuels, hydroelectric, solar,wind, oil, coal, photovoltaic, and nonrenewable resources.

What is energy?

1. Energy is the ability to cause change.

2. A moving object has kinetic energy thatdepends on the object’s mass and speed.

3. Potential energy is energy due to positionand depends on an object’s mass and height.

4. Light carries radiant energy, electric currentcarries electrical energy, and atomic nucleicontain nuclear energy.

Energy Transformations

1. Energy can be transformed from one formto another. Thermal energy is usually pro-duced when energy transformations occur.

2. The law of conservation of energy statesthat energy cannot be created or destroyed.

3. Electric power plants convert a sourceof energy into electrical energy. Steamspins a turbine which spins an electricgenerator.

Sources of Energy

1. The use of an energy source has advantagesand disadvantages.

2. Fossil fuels and nuclear energy are nonrenew-able energy sources that are consumed fasterthan they can be replaced.

3. Hydroelectricity is a renewable energysource that is continually being replaced.

4. Alternative energy sources include solar,wind, and geothermal energy. Solar energyis an inexhaustible energy source.

STUDY GUIDE 399

Thermal collector

EnergyResources

Renewable andinexhaustible

resources

Natural gas

ips.msscience.com/interactive_tutor(l)Lowell Georgia/CORBIS, (r)Mark Richards/PhotoEdit, Inc.

For each of the terms below, explain therelationship that exists.

1. electrical energy—nuclear energy

2. turbine—generator

3. photovoltaic—radiant energy—electricalenergy

4. renewable resource—inexhaustible resource

5. potential energy—kinetic energy

6. kinetic energy—electrical energy—generator

7. thermal energy—radiant energy

8. law of conservation of energy—energy transformations

9. nonrenewable resource—chemical energy

Choose the word or phrase that best answers thequestion.

10. Objects that are able to fall have what typeof energy?A) kinetic C) potentialB) radiant D) electrical

11. Which form of energy does light have?A) electrical C) kineticB) nuclear D) radiant

12. Muscles perform what type of energy transformation?A) kinetic to potentialB) kinetic to electricalC) thermal to radiantD) chemical to kinetic

13. Photovoltaics perform what type ofenergy transformation?A) thermal to radiantB) kinetic to electricalC) radiant to electricalD) electrical to thermal

14. The form of energy that food contains iswhich of the following?A) chemical C) radiantB) potential D) electrical

15. Solar energy, wind, and geothermal arewhat type of energy resource?A) inexhaustible C) nonrenewableB) inexpensive D) chemical

16. Which of the following is a nonrenewablesource of energy?A) hydroelectricityB) nuclearC) windD) solar

17. A generator is NOT required to generateelectrical energy when which of the fol-lowing energy sources is used?A) solar C) hydroelectricB) wind D) nuclear

18. Which of the following are fossil fuels?A) gas C) oilB) coal D) all of these

19. Almost all of the energy that is used onEarth’s surface comes from which of thefollowing energy sources?A) radioactivity C) chemicalsB) the Sun D) wind

400 CHAPTER REVIEW

alternative resource p. 391chemical energy p. 377electrical energy p. 378energy p. 374generator p. 384inexhaustible

resource p. 391kinetic energy p. 375law of conservation

of energy p. 380

nonrenewable resource p. 388

nuclear energy p. 378photovoltaic p. 392potential energy p. 376radiant energy p. 377renewable resource p. 390thermal energy p. 376turbine p. 384

ips.msscience.com/vocabulary_puzzlemaker

CHAPTER REVIEW 401

20. Explain how the motion of a swing illus-trates the transformation between poten-tial and kinetic energy.

21. Explain what happens to the kinetic energyof a skateboard that is coasting along a flatsurface, slows down, and comes to a stop.

22. Describe the energy transformations thatoccur in the process of toasting a bagel inan electric toaster.

23. Compare and contrast the formation of coaland the formation of oil and natural gas.

24. Explain the difference between the law ofconservation of energy and conservingenergy. How can conserving energy helpprevent energy shortages?

25. Make a Hypothesis about how spacecraft thattravel through the solar system obtain theenergy they need to operate. Do researchto verify your hypothesis.

26. Concept Map Copy and complete this con-cept map about energy.

27. Diagram the energy transformations thatoccur when you rub sandpaper on a pieceof wood and the wood becomes warm.

28. Multimedia Presentation Alternative sourcesof energy that weren’t discussed includebiomass energy, wave energy, and hydro-gen fuel cells. Research an alternativeenergy source and then prepare a digitalslide show about the information youfound. Use the concepts you learned fromthis chapter to inform your classmatesabout the future prospects of using suchan energy source on a large scale.

Radiant

Forms

Solar

Resources

Energy

ips.msscience.com/chapter_review

29. Calculate Number of Power Plants A certaintype of power plant is designed to pro-vide energy for 10,000 homes. How manyof these power plants would be needed toprovide energy for 300,000 homes?

Use the table below to answer questions 30 and 31.

30. Use Percentages According to the data inthe table above, what percentage of theenergy used in the United States comesfrom fossil fuels?

31. Calculate a Ratio How many times greateris the amount of energy that comesfrom fossil fuels than the amount ofenergy from all other energy sources?

Energy Sources Usedin the United States

Energy Source Percent of Energy Used

Coal 23%

Oil 39%

Natural gas 23%

Nuclear 8%

Hydroelectric 4%

Other 3%

CRCT PracticeCRCT Practice

Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

1. The kinetic energy of a moving objectincreases if which happens?A. Its mass decreases.B. Its speed increases.C. Its height above the ground increases.D. Its temperature increases.

Use the graph below to answer question 2.

2. By about how many times did global energyuse increase from 1970 to 2000?A. 1.5 timesB. 2 timesC. 3 timesD. 4 times

3. Which energy source is being used fasterthan it can be replaced? A. tidalB. windC. fossil fuelsD. hydroelectric

Use the circle graph below to answer question 4.

4. The graph shows the sources of electricalenergy in the United States. Large amountsof energy are measured in units calledquads. In 2002, the total amount ofelectrical energy produced in the UnitedStates was 38.2 quads. How much ofthis energy was produced by nuclear power plants? A. 3.0 quadsB. 3.8 quadsC. 7.6 quadsD. 35.1 quads

5. A softball player hits a fly ball. Whichdescribes the energy conversion that occursas the ball falls from its highest point? A. kinetic to potentialB. potential to kineticC. thermal to potentialD. thermal to kinetic

Coal51%

Oil3%

Otherrenewable3%

Nuclear20%

Gas14%

Hydro9%

Do Your Studying Regularly Do not “cram” the night beforethe test. It can hamper your memory and make you tired.

Global Oil Production

2050203020101990197019501930

5

10

15

20

25

30

0

Oil

pro

du

ctio

n (b

illio

ns

of b

arre

ls)

Year

These CRCT questions also provide practice for the NAEP science test.

402 CRCT PRACTICE

S8P2c

S8CS9f

S8P2b

655-CR-MSS08 744_IPS_GA.ps 1/24/07 11:38 PM Page 744

CRCT PracticeCRCT Practice

400350300250200150100

50

1985198019751970 1990 1995 20000

Global Energy Use 1970–2000

Year

Ener

gy

use

d (q

uad

rilli

on B

tu)

6. When chemical energy is converted intothermal energy, which is true?A. The total amount of energy changes.B. Only the amount of chemical energy

changes.C. Only the amount of thermal energy

changes.D. The total amount of thermal energy plus

chemical energy does not change.

Use the graph below to answer questions 7 and 8.

7. Approximately how many times greater wasoil production in 1970 than in 1950? A. 2 timesB. 10 timesC. 6 timesD. 3 times

8. In which year will global oil production bethe greatest? A. 1974B. 2002C. 2010D. 2050

Record your answers on a sheet of paper.

Use the graph below to answer questions 9–10.

9. The graph shows how the potential energyof a batted ball depends on the distancefrom the batter. At what distances is thekinetic energy of the ball the greatest?Explain.

10. At what distance from the batter is the height of the ball the greatest? Explain.

11. List advantages and disadvantages ofthe following energy sources: fossil fuels, nuclear energy, geothermal energy.

12. A basketball is dropped from a height of2 m and another identical basketball isdropped from a height of 4 m. Which basketball is moving faster just before it hits the ground? Explain.

Potential Energy of Batted Ball

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ips.msscience.com CRCT PRACTICE 403

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