Chapter 18: Energy - Wikispacesocala-chc.wikispaces.com/file/view/ch18.pdf · 538 CHAPTER 18 Energy...

532

sections

1 Energy ChangesLab Energy Conversions

2 Thermal EnergyLab Temperature Changes

Virtual Lab How is energy convertedfrom one form to another?

Snow SurfingWith no more than a board, a lot of snow,and a slope, this snowboarder goes fromstanding to moving at speeds greater than50 km/h. The snowboarder’s speed increasesbecause energy is changing form. In fact,energy changing form causes all the changesthat occur around you every day.

List three changes that you haveseen occur today, and describe what changed.Science Journal

Energy

Sunshine State Standards—SC.A.2: The student understands the basic principles of atomictheory; SC.B.1: recognizes that energy may be changed in form with varying efficiency.

Larry Prosor/SuperStock

533533

Energy Make the followingFoldable to help you under-stand the different ways energycan be transformed.

Fold a sheet of paper in halflengthwise.

Fold paper down2.5 cm from the top.(Hint: From the tip ofyour index finger toyour middle knuckleis about 2.5 cm.)

Open and drawlines along the 2.5cm fold. Label asshown.

Cause and Effect As you read the chapter, writeanswers to what each form of energy can bechanged to under the Changed To heading onyour Foldable. On the back of your Foldable,describe what caused each form of energy tochange and explain the effects of the change.

STEP 3

STEP 2

STEP 1

Changing Forms of EnergyThink of all the things you do every day, suchas riding to school, walking to class, and listening to music. All the things you do everyday involve changing energy from one formto another. When energy changes from oneform to another, changes occur.

1. Add sand to a plastic cup with a tight-fitting lid until it is about one-fourth full.

2. Using a thermometer, measure and recordthe temperature of the sand to the near-est tenth of a degree.

3. Place the lid on the cup. Hold the lid tight-ly in place and shake the cup vigorouslyfor five minutes.

4. Remove the lid and immediately measurethe temperature of the sand.

5. Think Critically How did the tempera-ture of the sand change? Describe thechanges that occurred in the sand as you shook the cup.

Start-Up Activities

Preview this chapter’s contentand activities at fl6.msscience.com

Form of

EnergyChanged

to

Electrical

Chemical

Thermal

Kinetic

Potential

SC.B.1.3.1

LA.B.2.3.1LA.A.1.3.4

Larry Prosor/SuperStock

http://fl6.msscience.com

Energy Energy is a term you probably use every day. You might say

that eating a plate of spaghetti gives you energy, or that a gym-nast has a lot of energy. Do you realize that a burning fire, abouncing ball, and a tank of gasoline also have energy?

What is energy? The word energy comes from the ancientGreek word energos, which means “active.” You probably haveused the word energy in the same way. When you say you have alot of energy, what does this mean? Energy is the ability to causechange. For example, energy can change the temperature of a potof water, or it can change the direction and speed of a baseball.The energy in a thunderstorm, like the one shown in Figure 1,produces lightning that lights up the sky and thunder that canrattle windows. Energy can change the arrangement of atoms inmolecules and cause chemical reactions to occur. You use energywhen you change the speed of a bicycle by pedaling faster orwhen you put on the brakes.

What does energy do?

■ Explain what energy is.■ Describe the forms energy takes.■ Describe how energy is used.

Energy causes all the changes thattake place around you.

Energy Changes

534 CHAPTER 18 Energy534

Figure 1 Lightning causesdramatic change as it lights upthe sky.

Benchmarks—SC.A.2.3.3 Annually Assessed (pp. 539–541): The student knows that radiation, light,and heat are forms of energy used to cook food, treat diseases, and provide energy; SC.B.1.3.1Annually Assessed (pp. 535–540, 543): identifies forms of energy and explains that they can bemeasured and compared; SC.B.1.3.2 (pp. 541, 543); SC.B.1.3.4 (p. 542); SC.B.2.3.1 (p. 542)

Also covers: SC.H.1.3.7 Annually Assessed (p. 543)

Review Vocabularyenergy transfer: a change in

energy from one form to another

New Vocabularyenergykinetic energypotential energythermal energycalorielaw of conservation of

energy

FCAT Vocabulary

Kennan Ward/CORBIS

SECTION 1 Energy Changes 535

Kinetic EnergyOne soccer ball is sitting on the ground and another is

rolling toward the net. How does the energy of the moving ballcompare to the one at rest? A moving ball certainly has the abil-ity to cause change. For example, a moving bowling ball shownin Figure 2 causes the bowling pins to fall. A moving ball hasenergy due to its motion. The energy an object has due to itsmotion is called kinetic energy. A football thrown by a quarter-back has kinetic energy. A sky diver or a leaf falling toward Earthalso has kinetic energy.

Mass, Speed, and Kinetic Energy Although movingobjects have kinetic energy, not all moving objects have the sameamount of kinetic energy. What determines the amount ofkinetic energy in a moving object? The amount of kinetic energyan object has depends on the mass and speed of the object, asshown in Figure 3 on the next page. Imagine a small rock and alarge boulder rolling down a hillside at the same speed. Whichwould have more kinetic energy? Think about the damage the rockand the boulder could do if they hit something at the bottom of thehill. The large boulder could cause more damage, so it has morekinetic energy. Even though the rock and the boulder were movingat the same speed, the boulder had more kinetic energy than therock because it had more mass.

Kinetic energy also depends on speed. The faster a bowlingball moves, the more pins it can knock down. When more pinsare knocked down, a greater change has occured. So the fasterthe bowling ball moves, the more kinetic energy it has. Kineticenergy increases as speed increases.

Figure 2 Any moving objecthas energy because it can causechange.Identify a change that the bowlingball is causing.

Food Contains ChemicalEnergy You transformenergy every time youeat and digest food. Thefood you eat containschemical energy. Yourbody changes this formof energy into otherforms of energy that keepyour body warm andmove your muscles. Theamount of chemical ener-gy contained in food ismeasured in Calories.Check some food labelsto see how many Caloriesyour food contains.

Alan Thornton/Getty Images

Figure 3

VISUALIZING KINETIC ENERGY

536 CHAPTER 18 Energy

The amount of kinetic energy of a moving object dependson the mass and the speed of the object.Energy is meas-ured in units called joules (J).For example, the fastest meas-

ured speed a baseball has been thrown is about 45 m/s.Thekinetic energy of a baseball traveling at that speed is about 150 J.

A 600-kg race car, traveling atabout 50 m/s, has about 5,000 timesthe kinetic energy of the baseball.

There is evidence that a meteorite 10 km indiameter collided with Earth about 65 million yearsago and might have caused the extinction ofdinosaurs.The meteorite may have been moving 400 times faster than the baseball and would have a tremendous amount of kinetic energy due to itsenormous mass and high speed—about a trillion trillion joules.

Earth’s atmosphere is continually bombarded byparticles called cosmic rays, which are mainly high-speed protons. The mass of a proton is about a 100trillion trillion times smaller than the mass of thebaseball. Yet, some of these particles travel so fast,they have nearly the same kinetic energy as thebaseball.

A sprinter with a mass of about 55 kg and running at 9 m/s has kinetic energy about 15 timesgreater than the baseball.

▼

▼

▼

▼

(tl)The Extinction of the Dinosaurs by Eleanor Kish, reproduced by permission of the Canadian Museum of Nature, Ottawa, Canada, (tr)W. Cody/CORBIS, (cr)William Swartz/Index Stock/PictureQuest, (bl)Duomo/CORBIS, (br)CORBIS


Potential EnergySuppose the ski lift in Figure 4 takes a skier to the top of a

hill. The skier has no kinetic energy when she is standing at thetop of the hill. But as she skis down and moves faster, her kineticenergy increases. Where does this kinetic energy come from?Gravity pulls the skier down the hill. If the skier were standingat the bottom of the hill, gravity would not start her moving, asit does when she is at the top of the hill. When the skier’s posi-tion is at the top of the hill, she has a form of energy calledpotential energy. Potential energy is energy that is storedbecause of an object’s position. By using the ski lift to take herto the top of the hill, the skier increased her potential energy bychanging her position.

Increasing Potential Energy When you raise an objectabove its original position, it has the potential to fall. If it doesfall, it has kinetic energy. To raise an object, you have to transferenergy to the object. The ski lift uses energy when it takes a skierup a hill and transfers some of that energy to the skier. Thisenergy becomes stored as potential energy in the skier. As theskier goes down the hill, the potential energy she had at the topof the hill is converted to kinetic energy.

If the skier were lifted higher, her potential energy wouldincrease. The higher an object is lifted above Earth, the greaterits potential energy.

Why did the skier’s potential energy increase asshe was carried up the hill?

The skier's potential energy increases as the ski lift carries her up the hill.

As she skis down the hill, potential energy transforms into kinetic energy.

Here her kinetic energy is greatest and her potential energy is smallest.

Her potential energy is largest at the top of the hill.

Figure 4 Potential and kineticenergy change as the skier movesup and down the slope.


Converting Potential and Kinetic EnergyWhen a skier skis down a hill, potential energy is trans-

formed to kinetic energy. Kinetic energy also can be trans-formed into potential energy. Suppose you throw a ball straightup into the air. The muscles in your body cause the ball to moveupward when it leaves your hand. Because it is moving, the ballhas kinetic energy. Look at Figure 5. As the ball gets higher andhigher, its potential energy is increasing. At the same time, theball is slowing down and its kinetic energy is decreasing.

What happens when the ball reaches its highest point? Theball comes to a stop for an instant before it starts to fall down-ward again. At its highest point the ball has no kinetic energybecause it isn’t moving. All the kinetic energy the ball had whenit left your hand has been converted to potential energy. As aresult, the ball will go no higher. As the ball falls downward, itspotential energy is converted back into kinetic energy.

Mechanical Energy The sum of the kinetic and potentialenergy of an object is the mechanical energy of the object. Themechanical energy of the ball wouldn’t change if potentialenergy is converted only into kinetic energy, and if kineticenergy is converted only into potential energy. However, as theball moves through the air, the force due to air resistance acts onthe ball. This force converts a small amount of the ball’smechanical energy into another form of energy—thermalenergy. As a result, the mechanical energy of the ball when youcatch it is slightly less than when you threw it upward.

What is the mechanical energy of an object?

KE PE KE PE KE PE

As the ball leaves the per-son’s hand, it is moving thefastest and has maximumkinetic energy.

As the ball moves upward, itslows down as its kineticenergy is transformed intopotential energy.

As the ball moves downward, itspeeds up as its potential energyis transformed into kineticenergy.

Figure 5 Energy is transformedas a ball rises and falls.

Comparing PotentialEnergyProcedure1. Hold a tennis ball about

1.5 m above a hard surface.2. Before the ball is dropped,

estimate the height theball will reach on each ofits first three bounces.

3. Drop the ball and have apartner use a meterstickto measure the height ofthe ball’s first threebounces.

Analysis1. When did the ball have the

greatest and least amountof potential energy?Explain.

2. Infer why the height of theball differed in each bounce.

3. How did the mechanicalenergy of the ball changeafter each bounce?

SC.B.1.3.2


Forms of EnergyBesides kinetic energy and potential energy, there are other

forms of energy. Some of these energy forms are due to motionand are a type of kinetic energy. Other energy forms are storedenergy and are a type of potential energy. Some of these formsof can be transferred from one object to another.

Thermal Energy All matter contains particles, such as atomsor molecules. The particles in matter are always moving. As aresult, these particles have energy that is due to their motion.The energy of the particles in matter due to their continualmotion is thermal energy. The thermal energy in an objectincreases when the object’s temperature increases.

How does the thermal energy of an objectchange when its temperature increases?

Electrical Energy When you plug a hair dryer into an electri-cal outlet and turn it on, another form of energy is being used—electrical energy. When the hair dryer is turned on, electricallycharged particles called electrons flow in various parts of thehair dryer. The energy of these flowing electrons is electricalenergy. As electrons flow in a hair dryer, their electrical energy isused to make an electric motor spin and to make parts of thehair dryer hot.

Chemical Energy The food that you eat is a source of energythat is used by your body. Food contains chemical compounds.Chemical compounds are made of atoms that are bondedtogether. The bonds between atoms store chemical energy.Because chemical energy is energy that is stored, it is a type ofpotential energy. Chemical energy is released when chemicalreactions occur. The chemical reactions that occur as your bodydigests food release chemical energy. This energy is used by yourbody to grow, to move, and in many other ways.

Radiant Energy When you sit in sunlight, you can feel thewarmth of the Sun on your skin. You feel warm because the Sungives off, or emits, a form of energy called radiant energy. Theradiant energy that comes from the Sun sometimes is calledsolar energy. Radiant energy is energy that is transferred bywaves from one place to another. The waves emitted by the Suntransfer radiant energy. These waves travel through space andstrike your skin, making it feel warm. Light also is a type of wavethat transfers radiant energy. Figure 6 shows examples of otherobjects that give off radiant energy.

Figure 6 Campfires, X-rayimages, and microwave ovens alluse radiant energy. Identify other objects that emitradiant energy.

A campfire is used to provide lightand warmth. A fire emits radiantenergy that you see as light andfeel as warmth.

X rays are waves that transfer radi-ant energy as they move fromplace to place. The radiant energytransferred by X rays is used toform images of the human body.

A microwave oven uses the radiantenergy transferred by microwavesto cook food.

(t)Getty Images, (c)Alfred Pasieka/Photo Researchers, (b)Stone/Getty Images


Nuclear Energy The Sun emits an enormous amount ofradiant energy every second. This energy is produced by reac-tions that occur in the Sun. However, these reactions aren’tchemical reactions. Instead, the Sun’s radiant energy is producedby reactions that involve the nuclei of atoms. Nuclear energy isenergy stored in the nucleus of an atom. This energy is releasedwhen changes occur in an atom’s nucleus.

Measuring EnergyRecall that in the SI system of units, time is measured in sec-

onds and distance is measured in meters. In the SI system ofunits, energy is measured using a unit called the joule (J). A stu-dent with a mass of 50 kg walking at a speed of 2 m/s has 100 Jof kinetic energy. The same student sitting on a ledge 1 m abovethe ground has about 500 J of potential energy.

Sometimes it is more convenient to measure energy usingother units. Another unit for energy is the calorie. One calorie isthe amount of energy needed to warm one gram of water by 1°C.One calorie (cal) is equal to about 4.19 J. A different energy unitis used to measure the energy content of food. This unit is theCalorie (with a capital C) and is equal to 1,000 cal, or 4,190 J.A candy bar that has 200 Calories supplies your body with almost838,000 J of energy.

Changing Forms of EnergyWhen you throw a ball into the air, the kinetic energy of the

ball changes into potential energy as the ball moves upward. Asthe ball falls, potential energy changes into kinetic energy as theball speeds up. As the ball rises and falls, one form of energychanges into another form of energy.

Every day, all around you and inside you, energy is changingfrom one form to another. Changes in forms of energy make acar move and make headphones produce sound. Inside yourbody chemical energy is changed to thermal energy, electricalenergy, and mechanical energy. All the events that you seearound you involve energy changing form.

Changing Electrical Energy Many of the devices you useevery day, like the one shown in Figure 7, change electricalenergy to other forms of energy. For example, hair dryers, CDplayers, and refrigerators contain electric motors. In an electricmotor, electrical energy makes the shaft of the motor spin, sothat electrical energy is changed to mechanical energy. Hair dry-ers and electric stoves contain heating elements that changeelectrical energy into thermal energy. A lightbulb produces lightby changing electrical energy to radiant energy.

Figure 7 An electric fan convertselectrical energy into other formsof energy.

Electricalenergy

Thermalenergy

Mechanicalenergy

Topic: Nuclear Reactions in the SunVisit fl6.msscience.com for Weblinks to information about thenuclear reactions that occur insidethe Sun.

Activity Draw a diagram show-ing the structure of the Sun andwhere in the Sun the nuclear reac-tions occur.

Annually AssessedBenchmark Check

SC.B.1.3.1 Compare and con-trast chemical energy and nuclearenergy.

FC

AT FOCUSF

C

AT FOCUS

LA.B.2.3.4

Digital Vision


Thermal energy


Changing Chemical Energy A differentenergy transfer is used by a stove that burns naturalgas. When a fuel like wood, gasoline, or natural gasis burned, chemical energy is changed into thermalenergy and light, or radiant energy. Figure 8 showsanother example of chemical energy changingform. When you light a candle, wax is burned toproduce thermal energy and light. In a car’s engine,gasoline is burned to produce thermal energy. Thecar converts this thermal energy to mechanicalenergy that enables the car to move. Your body usesfood as fuel. Chemical reactions in your bodychange the chemical energy stored in food to ther-mal energy and mechanical energy.

Using EnergyWhen you use a hair dryer, or toast bread in a

toaster, or listen to a CD, you are using energy. Ineach case, you used electrical energy to do some-thing—dry your hair, cook food, and make sound. When youburn a candle or heat water on the stove you are using chemicalenergy do something—provide light or heat water. Energy thatis used to do something or perform a task is useful energy.

The Law of Conservation of EnergyWhere does energy come from? Even though energy changes

from one form to another when it is used, energy never is createdor destroyed. According to the law of conservation of energy,energy never can be created or destroyed, but only can bechanged from one form to another.

Sometimes it might seem that energy is being lost. A booksliding on a table slows down and stops. The book’s kineticenergy decreased as it slowed down. Figure 9 shows what hap-pens to this energy. The kinetic energy of the book is notdestroyed, but is changed into another form of energy—thermalenergy. Friction causes the kinetic energy of the book to bechanged into thermal energy. This thermal energy makes thebook, the table, and the surrounding air slightly warmer.

Figure 9 As the book slidesalong the table, kinetic energy ischanged into thermal energy.When the book stops, all of itskinetic energy has been changedinto thermal energy.

Figure 8 Fireworks are a spec-tacular display of chemical energychanging to thermal energy andradiant energy.


SC.B.1.3.2 How much thermalenergy is produced in an electricmotor if 100 J of electrical energyare converted into 92 J of mechan-ical energy?

FC

AT FOCUSF

C

AT FOCUS

Randy Faris/CORBIS

Useful Energy Always DecreasesWhen energy is used, it usually is changed from

one form to another. For example, a battery in a flash-light converts chemical energy into electrical energy.This electrical energy is changed into useful radiantenergy by the flashlight bulb. However, some of theelectrical energy also is changed to thermal energy, asshown in Figure 10. When energy changes form,

some thermal energy is produced. Not all of this thermal energycan be used to do something useful. As a result, when energychanges form, the amount of useful energy is always less than theinitial amount of energy. Some energy always is changed into ther-mal energy that cannot be used to perform useful work.

When energy is changed from one form to another, itbecomes less concentrated and more spread out. For example,the electrical energy in a flashlight is concentrated in the batter-ies. When the flashlight is used, the light and thermal energyproduced is transferred to the air surrounding the flashlight.Compared to the energy in the batteries, the light and thermalenergy transferred to the air is spread out, and is less concen-trated. All energy conversions that occur cause energy tobecome more spread out and less concentrated.

Self Check1. Describe the energy transformations that occur when a

lightbulb is turned on.

2. Explain how the total energy changes when a fallingrock hits the ground.

3. Infer on which part of a roller coaster a roller coastercar has the greatest potential energy.

4. Determine which has the greater kinetic energy if bothare traveling at the same speed—a fully loaded truckor a motorcycle.

5. Think Critically When a ball is thrown upward, howdoes the height reached by the ball depend on itsinitial speed?

SummaryEnergy

• Energy is the ability to cause change.

• Kinetic energy is the energy an object hasbecause of its motion. Potential energy isstored energy.

Forms of Energy

• Energy comes in different forms. Some ofthese forms are thermal energy, electricalenergy, chemical energy, radiant energy, andnuclear energy.

• One form of energy can be changed intoanother form of energy.

Using Energy

• According to the law of conservation ofenergy, energy cannot be created ordestroyed, but only can change form.

• When energy changes form, some thermalenergy is produced and the amount of usefulenergy decreases.

6. Diagram the energy transformations that occur whenyou eat breakfast, walk to the bus stop, and ride thebus to school.

Batteries

Thermalenergy Light bulb

More Section Review fl6.msscience.com

Figure 10 The energy conver-sions in a flashlight produce somethermal energy that is not usefulenergy.


SC.B.2.3.1 Why does theamount of useful energy decreasewhen energy changes from oneform into another?

FC

AT FOCUSF

C

AT FOCUS


SC.B.1.3.1

SC.B.1.3.2

SC.B.1.3.1

SC.B.1.3.1

SC.B.1.3.2

SC.B.1.3.2


Have you ever watched one ball strike anotherball that is sitting still? What happens to theenergy of the first ball? Is all of the energytransferred to the second ball?

Real-World ProblemWhat are the energy conversions that occurwhen one ball strikes another ball?

Goals■ Measure the height changes in two balls

that are transferring energy.■ Observe the change in potential energy of

the two balls.

Materialsmetersticks (2)ring standhook collarstring (about 80 cm long)duct tapetennis balls (2)

Safety PrecautionsComplete a safety worksheet before you begin.

Procedure1. Make a data table in your Science Journal.

2. Assemble your ring stand, hook collar,string, and tennis balls as shown in the fig-ure. Secure the tennis balls to the ends ofthe string by tying and taping them.

3. Drape the string over the hook collar asshown in the figure. The string should touchthe hook at the halfway point on the string.Shorten the string if either ball touches thering stand or lab table.

4. Allow one ball to fall straight down. Makesure it is completely still.

5. Hold the other ball out at a 90° angle.Measure the height of the ball.

6. Drop the ball allowing it to strike the otherball. Record the height that each ballreaches for 5 passes.

Conclude and Apply1. How did the maximum height reached by

each ball change after each collision?

2. How did the mechanical energy of the ballchange?

3. Why did the mechanical energy of the ballchange after each collision?

Energy Conversions

Compare your data to the data collected byyour classmates. Discuss and explain anydifferences you observe in the collected data.

LAB 543

Benchmark—SC.B.1.3.1: The student identifies forms of energy and explains that theycan be measured and compared; SC.B.1.3.2: The student knows that energy cannot becreated or destroyed, but only changed from one form to another; SC.H.1.3.7: The stu-dent knows that when similar investigations give different results, the scientific chal-lenge is to verify whether the differences are significant by further study.

Matt Meadows

TemperatureWhat’s today’s temperature? If you looked at a thermometer,

listened to a weather report on the radio, or saw a weather mapon television, you probably used the air temperature to help youdecide what to wear. Some days are so hot you don’t need ajacket. Others are so cold you want to bundle up.

Hot and cold are words used in everyday language to describetemperature. However, they are not scientific words becausethey mean different things to different people. A summer daythat seems hot to one person might seem just right to another.If you grew up in Florida but moved to Minnesota, you mightfind the winters unbearably cold. Have you ever complainedthat a classroom was too cold when other students insisted thatit was too warm?

Particles are in Random Motion What is temperature?Remember that any material or object is made up of atoms ormolecules. These particles are moving constantly, even if theobject appears to be perfectly still. Every object you can thinkof—your hand, the pencil on your desk, or even the desktop—contains particles that are in constant motion. In solids, liquids,and gases particles do not move in a single direction. Insteadthey move in all directions. In a gas, particles are far apart and

can move, as shown in Figure 11.In liquids, atoms are close togetherand can’t move as far as in a gas. Insolids, particles are bound moretightly together than in a liquid.Instead of moving freely as shownin Figure 11, atoms or molecules ina solid vibrate back and forth. Themotion of particles in all directionsin solids, liquids, and gases is calledrandom motion. Because the parti-cles are moving, they have kineticenergy. The faster the particles aremoving, the more kinetic energythey have.

Thermal Energy

■ Distinguish between tempera-ture, heat, and thermal energy.

■ Explain how thermal energymoves.

The flow of thermal energy warmsEarth, produces weather, cooks yourfood, and warms and cools yourhome.

Figure 11 In gases, atoms ormolecules are free to move in alldirections.


Benchmarks—SC.A.1.3.3 (pp. 544–545, 550, 552–553): The student knows that temperature measuresthe average energy of motion of the particles that make up the substance; SC.B.1.3.5 (pp. 548–551): Thestudent knows the processes by which thermal energy tends to flow from a system of higher tempera-ture to a system of lower temperature.

Also covers: SC.H.1.3.4 Annually Assessed (pp. 552–553), SC.H.1.3.5 Annually Assessed (pp. 550,552–553), SC.H.1.3.7 Annually Assessed (pp. 552–553)

Review Vocabularymolecule: a particle formed whentwo or more atoms bond together

New Vocabulary

• temperature convectionheat radiationconduction

FCAT Vocabulary

SECTION 2 Thermal Energy 545

Temperature and Kinetic Energy Temperature is a meas-ure of the average kinetic energy of the particles in an object.When an object’s temperature is higher, its atoms or moleculeshave more kinetic energy. Figure 12 shows gas molecules at twotemperatures. At the higher temperature, the molecules are mov-ing faster and have more kinetic energy.

Figure 12 Temperaturedepends on the average kineticenergy of the atoms or molecules.

The gas molecules move sloweron average at a lower tempera-ture. Gas molecules movefaster on average at a highertemperature.

Can you be fooled by temperature?

On a cold morning, you might have heard a meteorologist give the wind chillindex, as well as the temperature. Although wind cannot lower the temperature

of the outside air, it can make you feel as if the temperature were lower.

Identifying the Problem A wind chill index of –29°C pres-

ents little danger to you if you areproperly dressed. Below this tempera-ture, however, your skin can becomefrostbitten within minutes. Use thetable to find wind chill values forconditions that present the greatestdangers.

Solving the Problem 1. Assuming you live in an area where

wind speeds in the winter rarelyreach 50 km/h, at which air temper-ature should you be certain to takeextra precautions?

2. What happens to the wind chillindex as wind speeds get higher andtemperatures get lower?

Wind Chill Index

Temperature Wind Speed (km/h)

(°C)

10 20 30 40 50 60 70 80

20 18°C 16°C 14°C 13°C 13°C 12°C 12°C 12°C

12 9°C 5°C 3°C 1°C 0°C 0°C �1°C �1°C

0 �4°C �10°C �14°C �17°C �18°C �19°C �20°C �21°C

�20 �26°C �36°C �43°C �47°C �49°C �51°C �52°C �53°C

�36 �44°C �57°C �65°C �71°C �74°C �77°C �78°C �79°C


Measuring TemperatureSome people might say that the water in a swimming pool feels

warm, although others might say it feels cool. Because the temper-ature of the water feels different to different people, you cannotdescribe or measure temperature accurately by how it feels.Remember that temperature is related to the kinetic energy of allthe atoms in an object. You might think that to measure tempera-ture, you must measure the kinetic energy of the atoms. But atomsare so small that even a tiny piece of material consists of trillionsand trillions of atoms. Because they are so small and objects con-tain so many of them, it is impossible to measure the kinetic ener-gy of all the individual atoms. However, a practical way to measuretemperature is to use a thermometer.

Why can’t the kinetic energy of all the atoms inan object be measured?

The Celsius Scale A temperature scale that is used widelythroughout the world is the Celsius (SEL see us) scale. On theCelsius temperature scale, the freezing point of water is giventhe temperature 0°C and the boiling point is given the tempera-ture 100°C as shown in Figure 13.

What are the boiling and freezing points ofwater on the Celsius temperature scale?

Figure 13 This thermometeruses the height of a liquid in a tubeto measure temperature. The liq-uid height changes with tempera-ture because the liquid expands asits temperature increases. Thethermometer is calibrated bymarking the liquid height at twoknown temperatures.

Boilingwater

Mark heightof liquid

Glass tube

Ice cube

Liquid

Mark heightof liquid

Beaker

The height of the liquid is markedwhen the thermometer is placed inwater at 0°C.

The height of the liquid is markedwhen the thermometer is placedin boiling water at 100°C.

Freezing point0°C

Boiling point100°C

One hundred equal divisions

Make a temperature scaleby dividing the distancebetween the two marksinto equal degrees.


The Fahrenheit Scale One temperature scale you might befamiliar with is the Fahrenheit (FAYR un hite) scale. TheFahrenheit scale currently is used mainly in the United States.On the Fahrenheit scale, the freezing point of water is given thetemperature 32°F, and the boiling point is 212°F.The space between the boiling point and thefreezing point is divided into 180 equal degrees.Because there are only 100 Celsius degreesbetween the boiling and freezing points of water,a temperature change of one Celsius degree isbigger than a change of one Fahrenheit degree.

Thermal Energy and HeatRecall that thermal energy is the energy of

the particles in an object due to their randommotion. As the temperature of the objectincreases, the particles move faster and the ther-mal energy of the object increases. Thermalenergy can be transferred between objects at dif-ferent temperatures.

For example, thermal energy is transferredwhen you hold a glass of iced tea, as shown in Figure 14. As youhold the glass of iced tea, the tea warms up. Thermal energymoves from your hand to the iced tea. The thermal energyadded to the tea causes the kinetic energy of the particles in thetea to increase. As a result, the temperature of the tea increases.

A transfer of thermal energy from a substance at a highertemperature to a substance at a lower temperature is heat.Thermal energy will stop moving from your hand to the iced teaonly when both are at the same temperature.

Temperature Changes Depend on the Material

When the temperature of a material changes, thermal energyhas been transferred to the material or from the material. Thetemperature change depends on the amount of thermal energytransferred. It also depends on the amount of material and thetype of material. For example, water is an unusual material.Compared to equal amounts of other materials, the temperatureof water rises more slowly as it absorbs thermal energy. As aresult, water is often used as a coolant. Water is used in a car’scooling system to absorb thermal energy produced by theengine, as shown in Figure 15. This keeps the engine tempera-ture low enough to prevent damage from overheating.

Figure 14 Your hand is warmerthan the iced tea. The particles inyour hand are moving faster andhave more thermal energy thanthe particles in the tea.

Figure 15 A car overheats whenthe cooling system doesn’t absorbenough thermal energy from theengine.

(t)Mark Burnett, (b)Paul Barton/The Stock Market/CORBIS


Lakes and Air Temperature How does the temperature ofwater in a lake compare to the temperature of the surroundingair on a hot summer day? You might have noticed that the wateris cooler than the air during the day and warmer than the air atnight. This is because it takes longer for a large body of water towarm up or cool down than it does for the surrounding air andland to change temperature. Even from season to season, a largebody of water can change temperature less than the surround-ing land, as shown in Figure 16.

Thermal Energy on the MoveA transfer of thermal energy occurs if there is a temperature dif-

ference between two areas in contact. Thermal energy is transferredfrom warm places to cooler ones. This transfer can take place inthree ways—radiation, conduction, and convection. Conductiontransfers thermal energy mainly through solids and liquids.Convection transfers thermal energy through liquids and gases.Radiation can transfer thermal energy through space.

Conduction Have you ever picked up a metal spoon that wasin a pot of boiling water? The spoon handle became hot becauseof conduction. Conduction (kun DUK shun) is the transfer ofthermal energy by collisions between the atoms and molecules ina material.

As the part of the spoon in the boiling water became warmer,its atoms and molecules moved faster. These particles then col-lided with slower-moving particles in the spoon. In these colli-sions, thermal energy was transferred from the faster-moving tothe slower-moving particles farther up the spoon’s handle.

Winter Summer

During the summer, the lake is cooler than thesurrounding land.

During the winter, the lake is warmer than thesurrounding land.

Figure 16 Water can absorb andlose a great deal of heat without alarge temperature change.

The Caloric Theory Atone time heat wasthought to be a fluidcalled caloric. In the lateeighteenth century,Benjamin Thompsonnoticed that largeamounts of thermal ener-gy were generated dur-ing the boring of theholes in cannons. He con-cluded the amount ofthermal energy produceddepended only on thework done by the drill.James Joule later showedthat other forms of ener-gy could be convertedinto thermal energy.Research how the workof Thompson and Jouledisproved the caloric theory.

LA.A.2.3.5

David Higgs/CORBIS


Conduction in a Solid When conduction occurs, thermalenergy is transferred. However, in a solid, the particles don’tmove from place to place. Instead, they vibrate back and forth,bumping into each other. These collisions transfer energy fromparticle to particle, while the particles stay in place.

How is energy transferred by conduction?

Conductors Conduction transfers thermal energy from oneplace to another. However, thermal energy moves at differentspeeds in different materials. Materials in which thermal energymoves easily are called thermal conductors. Most metals aregood conductors of thermal energy. Metals such as gold, silver,and copper are the best thermal conductors. Copper is a widelyused conductor because it is less expensive than gold or silver.Copper often is used in cooking pans. A pan with a copper bot-tom conducts thermal energy more evenly. It helps spread ther-mal energy across the bottom surface of the pan to prevent hotspots from forming. Some cooking pans are made of steel buthave copper bottoms. This allows food to cook evenly.

Insulators Some materials are poor conductors of thermalenergy. These materials can be used as thermal insulators. Whenyou are cold, for example, you can put on a sweater or a jacketor add another blanket to your bed. You are keeping yourselfwarm by adding insulation. The clothes and the blanket arepoor conductors of thermal energy. In fact, they make it moredifficult for thermal energy to escape from your body. By trap-ping the thermal energy your body produces,you feel warmer.

Blankets and clothes help keep you warmbecause they are made of materials that con-tain many air spaces, as shown in Figure 18.Air is a good insulator. Materials that containair also are good insulators. For example,building insulation is made from materialsthat contain air spaces.

Materials made of plastics also are oftengood insulators. If you put a plastic spoon inboiling water, it takes a long time for it to gethot. Many cooking pans have plastic handlesthat won’t melt instead of metal ones. Thesehandles remain at a comfortable temperaturewhile the pans are used for cooking. Otherexamples of insulators include wood, rubber,and ceramic materials such as tiles.

Figure 17 In a solid, particlescollide with each other as theyvibrate back and forth.

Figure 18 Under high magnifi-cation, this insulating material isseen to contain many air spaces.Explain how increasing the num-ber of air spaces in a materialaffects the movement of thermalenergy.

Magnification: notavailable

Thinsulate is a trademark of 3M. Photo courtesy 3M

An animated version of this diagram is available atfl6.msscience.com


Some Materials Feel Hotter Think about getting into acar that has been sitting in sunlight on a hot day. Would yourather sit on a vinyl-covered seat or a fabric-covered seat? Evenif the temperatures of the seats are the same, the vinyl seat feelshotter than the fabric seat. How hot something feels depends onhow quickly thermal energy moves in the material, as well as thetemperature of the material. Vinyl is a better thermal conductorthan fabric, so thermal energy flows to your skin more rapidlyfrom the vinyl seat than from the fabric seat. As a result, thevinyl feels hotter than the fabric does.

Convection Thermal energy also can be transferred by parti-cles that move from one place to another. Convection transfersthermal energy when particles move between objects or areasthat have different temperatures. This type of energy transfer ismost common in gases and liquids. As temperature increases,particles move around more quickly, and the distance betweenparticles increases. This causes density to decrease as tempera-ture increases. Cooler, denser material then forces the warmer,less dense material to move upward.

Some homes are heated by convection. Look at Figure 19.Air is warmed in the furnace. The warm, less dense air is thenforced up through the air duct by the furnace fan. The warm airgets pushed up through the room by the cooler air around it. Asthe warm air cools, it becomes more dense. Cool, dense air sinksand is then pulled into the return air duct by the furnace fan tobe warmed again and recirculated.

Figure 19 The furnace’s fanhelps circulate hot air through yourhome. Warmer air moves upwardwhile cooler air moves downward.Explain why the hot air ducts areplaced near the floor.

Exhaust

Hot air Cold air

Air duct

Furnace

Fan

Comparing EnergyContentProcedure1. Pour equal amounts of

hot, cold, and room-temperature water intoeach of three transpar-ent, labeled containers.

2. Measure and record thetemperature of the water in each container.

3. Use a dropper to gently put a drop of food color-ing in the center of eachcontainer.

4. After 5 min, observe eachcontainer.

Analysis1. Based on the speed at

which the food coloringspreads through the water,rank the containers fromfastest to slowest.

2. Infer how water tempera-ture affected the move-ment of the food coloring.

3. In which container do thewater particles have themost kinetic energy?

SC.A.1.3.3SC.H.1.3.5



Self Check1. Explain how the motion of particles in an object

changes when its temperature increases.

2. Explain why some insulating materials contain small airspaces.

3. Identify the type of thermal energy transfer that cantake place with little or no matter present. Explain.

4. Think Critically Popcorn is cooked in a hot-air popper,in a microwave oven, or in a pan on a stove. Identifyhow thermal energy is transferred in each case.

SummaryTemperature

• The particles that make up an object are inconstant random motion.

• The temperature of an object is a measure ofthe average kinetic energy of the particles inthe object.

Thermal Energy and Heat

• Heat is a transfer of thermal energy due to adifference in temperature.

• Thermal energy always flows from a highertemperature to a lower temperature.

• Conduction, convection, and radiation areways thermal energy is transferred.

• Insulators are materials in which thermalenergy does not flow easily.

5. Convert Temperature To change a temperature fromFahrenheit to Celsius, subtract 32 from the Fahrenheittemperature, then multiply by 5/9. If the temperatureis 77°F, what is the Celsius temperature?

Examples of ConvectionEagles and hawks float effort-

lessly high in the air. Sometimes a bird can stay in theair without flapping its wings because it is held up bya thermal.

As shown in Figure 20, a thermal is a column ofwarm air that is forced up as cold air around it sinks.It is a convection current in the air.

Convection also occurs in liquids. In a pot of boil-ing water, the warmer, less dense water is forced up asthe cooler, denser water sinks. Convection currentson a larger scale are formed in oceans by cold waterflowing from the poles and warm water flowing fromtropical regions.

Radiation The transfer of thermal energy bywaves is radiation (ray dee AY shun). These wavescan be visible light waves or types of waves that you cannot see.When these waves strike an object, their energy can be absorbedand the object’s temperature rises. Radiation can travel throughair and even through a vacuum.

The Sun transfers energy to Earth by radiation. When youstand by a fire, radiation makes you feel warm. Thermal energyis transferred by radiation from the fire and you become warmer.You also can use radiation to cook food. A microwave oven cooksfood by using microwave radiation to transfer energy to the food.

Figure 20 Thermals form whenhot, less-dense air is pushedupward by cooler, denser air.

More Section Review fl6.msscience.com

MA.B.2.3.2

SC.A.1.3.3

SC.B.1.3.5

SC.B.1.3.5

SC.B.1.3.5

fl6.msscience.com

Light from the Sun

Light energy heats up the ground.

Air heats up nearthe surface, expands,and is pushed upward.

Cool,dense

air

Cool,dense

air

Hot,less

denseair



Temperature Changes


Real-World ProblemSometimes a bowl of soup can be too hot to eat, and you have to waitfor the soup to cool. How long does it take for hot soup to cool? Doesthe soup cool faster if it isn’t as hot? In this lab, you will investigatehow the temperature of water changes over time.

Procedure1. Copy the data table into your Science Journal. Work in teams of

three. Decide who will be the timekeeper, who will read the ther-mometers and stir the beakers, and who will record observations.

2. Fill one beaker with the ice and 100 mL of water. Add 100 mL ofwater to another beaker.

3. Heat 100 mL of water in the third beaker until it is about 70°C.Remove the beaker from the heat source.

4. Remove the ice from the first beaker and put a thermometer ineach of the three beakers. Record the beginning temperatures ofthe three beakers of water.

5. Predict what will happen to the temperatures of each of the threebeakers of water as they sit at room temperature for 15 minutes.Record your predictions in your Science Journal.

Goals■ Predict how cold and

warm water willchange over time in aroom-temperatureenvironment.

■ Measure the tempera-ture changes that occurover time.

Materials thermometers (3)stirring rods (3)400-mL beakers (3)300 mL of waterstop watch or clock with

second handhot plateicepaper towelsgraph paper

Safety Precautions

Complete a safety work-sheet before you begin.

WARNING: Do not usemercury thermometers.Use caution when heatingwater with a hot plate.

Benchmark—SC.A.1.3.3: The student knows that temperature measures the averageenergy of motion of the particles that make up the substance; SC.H.1.3.4: knows thataccurate record keeping, openness, and replication are essential to maintaining aninvestigator’s credibility with other scientists and society; SC.H.1.3.5: knows that achange in one or more variables may alter the outcome of an investigation; SC.H.1.3.7:knows that when similar investigations give different results, the scientific challenge isto verify whether the differences are significant by further study.

Matt Meadows

6. At one minute intervals, have the timekeeper notify the thermometer reader totake a reading. The reader should read the temperature of each beaker of waterin the same order every minute. Continue taking readings for 15 minutes.

7. Graph your data. Using a different color pencil for each beaker, plot the timeand temperature data from the cold, lukewarm, and hot water on one x-axisand y-axis. Connect the points for each graph with a curve.

8. Extend the curve for each graph to predict how the temperature in each beakerwould change if you took temperature readings for five additional minutes.

Analyze Your Data1. Explain what the extended temperature curves appear to do.

2. Describe how your predictions compare to your results.

Conclude and Apply1. Predict what would happen if you combined the

warm water with the room temperature water.

2. Infer what you could do to slow the change intemperature among the beakers. How couldyou speed it up?

Compare your results with other studentsin your class. Discuss any differences in thedata and infer reasons for these differences.

LAB 553

Data Table

Time Cold Water (°C) Warm Water (°C) Room Temp. Water (°C)

Start

1 min

2 min

3 min

4 min

5 min

6 min

7 min

8 min

Do not write in this book.

Hiroshimaby Lawrence Yep

On August 6, 1945, an American B-29 bomber dropped a

new weapon called the atom bomb on the Japanese city

of Hiroshima. The bomb destroyed 60 percent of the city,

killing between 90,000 and 140,000 people.

Everything is made up of tiny particles called

atoms. They are so small they are invisible to

the eye. Energy holds these parts together like

glue. When the atom breaks up into its parts, the

energy goes free and there is a big explosion.

Inside the bomb, one uranium atom collides with

another. Those atoms both break up. Their parts

smash into more atoms and split them in turn.

This is called a chain reaction. There are millions

and millions of atoms inside the bomb. When they

all break up, it is believed that the atom bomb will be

equal to 20,000 tons of dynamite. In 1945, it is the

most powerful weapon ever made….

Up until then, no single bomb has ever caused so

much damage or so many deaths.

The wind mixes their dust with the dirt and debris.

Then it sends everything boiling upward in a tall

purple-gray column. When the top of the dust cloud

spreads out, it looks like a strange, giant mushroom.

The bomb goes off 580 meters above the ground.

The temperature reaches several million degrees

Celsius immediately.

One mile away, the fierce heat starts fires.

Even two miles away, people are burned by

the heat.

Respond to the Reading1. What was the author’s reason for

writing this piece?2. How is the atom bomb different from

other bombs?3. Linking Science and Writing Write a

one- or two-paragraph summary of oneof the sections in this chapter.

Energy can bereleased by chemical

reactions when the bonds between atoms arebroken. In this excerpt from Hiroshima,Lawrence Yep describes the effects of theenergy released in a different process—theenergy released when the nuclei of atoms aresplit. This reaction released an enormousamount of energy that destroyed a city.

UnderstandingLiteratureSummarize When you summarizesomething, you mention only the mainideas and necessary supporting details.The author of Hiroshima has chosen tosummarize the events. He briefly explainsthe science behind the atom bomb. Healso gives some details about the destruc-tion after the bomb was dropped onHiroshima, Japan. How are summariesuseful?


LA.B.2.3.1

Energy due to positionForm of energy that depends

on temperature

Energy

Temperature

Conduction

Transferred whenparticles move from one

place to another

Copy and complete the following concept map on energy.

Energy Changes

1. Energy is the ability to cause change.

2. Energy can be transformed from one forminto another.

3. Kinetic energy is the energy an object hasdue to its motion. Kinetic energy increasesas the speed of an object increases.

4. Potential energy is stored energy thatincreases as an object’s height increases.

5. According to the law of conservation of energy, energy is never created ordestroyed, but only changes form.

6. When energy is changed from one form toanother, some thermal energy is producedand the amount of useful energy decreases.

Thermal Energy

1. The temperature of a material is a measureof the average kinetic energy of the parti-cles in the material.

2. The most widely used temperature scale isthe Celsius scale. The Fahrenheit tempera-ture scale is used in the United States.

3. Thermal energy is the energy contained inan object that depends on the object’s temperature.

4. Heat is the transfer of thermal energy from ahigher temperature to a lower temperature.

5. Thermal energy can be transferred fromone place to another by conduction, con-vection, and radiation.

CHAPTER STUDY GUIDE 555Interactive Tutor fl6.msscience.com


Fill in the blanks with the correct vocabularyword or words.

1. A(n) _________ is a unit of energy.

2. The energy due to motion is _________.

3. The movement of thermal energy fromwarm to cool objects is _________.

4. Energy that is due to the random motionof the particles in a material is _________.

5. _________ is energy that is stored.

6. _________ is the transfer of thermalenergy by collisions between the particlesin a material.

7. The transfer of thermal energy by waves iscalled _________.

8. The transfer of thermal energy by particlesmoving from one place to another is_________.

9. _________ is the ability to cause change.

Choose the word or phrase that best answers thequestion.

10. Which of the following correctlydescribes energy?A) can be createdB) can be destroyedC) cannot change formD) can change form

11. The average kinetic energy of the particlesin an object is related to which of the following? A) chemical energy C) temperatureB) heat D) useful energy

12. The transfer of thermal energy due to themovement of warm air in a room is anexample of which process? A) convectionB) temperatureC) conductionD) potential energy

13. Which of the following describes how thetotal amount of energy changes during anenergy transformation?A) It increases.B) It decreases.C) It stays the same.D) It all becomes thermal energy.

14. How is energy from the Sun transferred toEarth?A) It is transferred by conduction.B) It is transferred by convection.C) It is transferred by radiation.D) It is transferred by contact.

15. When would you have the mostpotential energy?A) walking up the hillB) sitting at the top of the hillC) running up the hillD) sitting at the bottom of the hill

16. What form of energy is always producedwhen energy changes from one form toanother? A) radiant C) thermalB) chemical D) electrical

17. Thermal energy moves most easily inwhich of these materials? A) plastic C) airB) wood D) copper

556 CHAPTER REVIEW

calorie p. 540conduction p. 548convection p. 550energy p. 534heat p. 547kinetic energy p. 535

law of conservationof energy p. 541

potential energy p. 537radiation p. 551temperature p. 545thermal energy p. 539

Vocabulary PuzzleMaker fl6.msscience.com

FCAT Vocabulary

SC.B.1.3.2

SC.A.1.3.3

SC.B.1.3.5

SC.B.1.3.2

SC.B.1.3.5

SC.B.1.3.1

SC.B.1.3.4

SC.B.1.3.5


CHAPTER REVIEW 557

18. Concept Map Below is a concept map on theenergy changes that occur when a personjumps upward. Copy and complete themap by indicating the type of energy—kinetic, potential, or both—the person hasat each of the following stages: halfway up,the highest point, halfway down, and justbefore hitting the ground.

19. Infer When a ball falls and hits the ground,how does the initial potential energy ofthe ball compare with the amount of ther-mal energy produced?

Use the table below to answer question 20.

20. Make a Graph Using the data in the tableabove, graph the kinetic energy of the ballon the y-axis and the speed of the ball onthe x-axis. Describe the shape of your graph.How does the kinetic energy change whenthe speed doubles?

21. Explain why the amount of useful energyalways decreases when energy is changedfrom one form to another.

22. Explain why the walls of houses often arefilled with fiberglass insulation.

23. Determine the energy transformations thatoccur in each of the following situations—alog burns in a fireplace, a ball is dropped, aslice of pizza is heated in a microwave oven.

24. Explain why a blanket is a better conductorof heat when it is wet than when it is dry.

25. Design an Experiment to determine how quicklythe temperature of different materialschanges as they absorb radiant energy. Usethe following items—three different colorsof construction paper, three thermometers,and a sunny window or a heat lamp.

Kinetic Energy of a Ball

Speed of Ball (m/s) Kinetic Energy (J)

5 2.5

10 10.0

15 22.5

20 40.0

25 62.5

30 90.0

just after jumping

KineticEnergy

Fahrenheit and Celsius Temperatures

Celsius Temperature (°C) Fahrenheit Temperature (°F)

100 212

50 122

0 32

�25 �13

�50 �58

Use the table below to answer question 26.

26. Temperature Scales Graph the data in thetable with the Celsius temperature on the x-axis and the Fahrenheit temperature onthe y-axis. From your graph, determine thetemperature that has the same value on bothtemperature scales.

Chapter Review fl6.msscience.com

SC.B.1.3.1

SC.B.1.3.2

SC.B.1.3.1

SC.B.1.3.5

SC.B.1.3.4

SC.B.1.3.2

SC.A.2.3.3

SC.B.1.3.5

MA.E.1.3.1


558 FLORIDA

a The illustration below shows how a roomis heated by a furnace.

How does the air at point G compare tothe air at point H?

A. The air at point G is warmer but hasthe same density.

B. The air at point G is cooler and ismore dense.

C. The air at point G is cooler but has agreater density.

D. The air at point G is warmer and lessdense.

s Which of the following is an example ofan object with kinetic energy?

F. a ball lying in the grass

G. a pencil resting on a desk

H. an apple falling to the ground

I. a skier waiting at the top of a hill

ExhaustAir duct

Furnace

Fan

G H

d How does thermal energy flow as you holda glass of iced tea?

A. by radiation from the ice to your hand

B. by convection from the ice to yourhand

C. by conduction from your hand to theglass

D. by convection from your hand to theglass

f The illustration below shows the energytransformations that occur in a flashlight.

How much thermal energy is produced bythe bulb if 42.0 joules (J) of electricalenergy are changed into 4.2 J of radiantenergy?

F. 4.2 J

G. 37.8 J

H. 42.0 J

I. 46.2 J

Light bulb

Batteries

Thermalenergy

SC.B.1.3.5

SC.B.1.3.2

SC.B.1.3.5

SC.B.1.3.4

FloridaFloridachapter chapter

The assessed Florida Benchmark appears above each question.Record your answers on the answer sheet provided by your teacher or on a sheet of paper.

FC

AT FOCUSF

C

AT FOCUS

FCAT PRACTICE 559FCAT Practice fl6.msscience.com

g Shaun is using a ball to experiment withpotential energy. Which should Shaun doto increase the ball’s potential energy?

A. The ball should be rolled down a ramp.

B. The ball should be cooled.

C. The ball should be dropped.

D. The ball should be lifted higher.

h At which temperature is the averagekinetic energy of molecules the largest?

F. 30°C

G. 20°C

H. 10°C

I. �5°C

j The diagram below shows a wind chillindex.

If the outside temperature is 12°C, at whatwind speed in kilometers per hour (km/h)will the wind chill be the same as thefreezing point of water?

k Explain why when foods are placed in arefrigerator, the temperature of frozenfoods increases, while the temperature ofhot foods decreases.

l The illustration below shows a rollercoaster. The labels show different positionsof the roller-coaster car as it travels overthe tracks.

PART A Describe how the energy in aroller-coaster car is continuallytransformed as it moves fromleft to right along the track.

PART B Compare and contrast thekinetic and potential energy ofthe roller-coaster car at points F,G, H, and K.

F

GK

H

READINQUIREEXPLAIN

READINQUIREEXPLAIN

Wind Chill Index

Temperature(°C)

Wind Speed (km/h)

20 30 40 50 60

20 16°C 14°C 13°C 13°C 12°C

12 5°C 3°C 1°C 0°C 0°C

0 �10°C �14°C �17°C �18°C �19°C

�20 �36°C �43°C �47°C �49°C �51°C

�36 �57°C �65°C �71°C �74°C �77°C

SC.B.1.3.1

SC.A.1.3.3

SC.B.1.3.5

SC.B.1.3.5

SC.B.1.3.1

FCAT PracticeFCAT Practice FC

AT FOCUSF

C

AT FOCUS

Be Prepared Bring at least two sharpened No. 2 pencils and agood eraser to the test. Before the test, check to make surethat your eraser erases completely.


Chapter 18: Energy - Wikispacesocala-chc.wikispaces.com/file/view/ch18.pdf · 538 CHAPTER 18 Energy...

Documents

Transcript of Chapter 18: Energy - Wikispacesocala-chc.wikispaces.com/file/view/ch18.pdf · 538 CHAPTER 18 Energy...