OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES Compression guide: To shorten instruction because of time limitations, omit Section 4. 9 Energy and Energy Resources Chapter Planning Guide Chapter Opener 237A Chapter 9 • Energy and Energy Resources OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P32 Energy and Work* TR P33 Thermal Energy in Water* CRF SciLinks Activity* g SE Internet Activity, p. 244 g CD Science Tutor TE Demonstration Forms of Energy, p. 240 g TE Demonstration All Wound Up!, p. 241 g TE Activity El Niño, p. 244 a SE Quick Lab Hear That Energy!, p. 245 g CRF Datasheet for Quick Lab* LB Whiz-Bang Demonstrations Wrong-Way Roller?* b LB Calculator-Based Labs Power of the Sun* a Section 1 What Is Energy? • Explain the relationship between energy and work. • Compare kinetic and potential energy. • Describe the different forms of energy. OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P34 Potential Energy and Kinetic Energy* TR P35 From Light Energy to Chemical Energy* TR LINK TO LINK TO LIFE SCIENCE LIFE SCIENCE L46 Photosynthesis* TR P36 Energy Conversions in a Bicycle* VID Lab Videos for Physical Science CD Science Tutor TE Connection Activity Environmental Science, p. 250 g SE Skills Practice Lab Finding Energy, p. 264 g CRF Datasheet for Chapter Lab* SE Skills Practice Lab Energy of a Pendulum, p. 723 g CRF Datasheet for LabBook* LB Whiz-Bang Demonstrations Pendulum Peril * b PACING • 90 min pp. 248–253 Section 2 Energy Conversions • Describe an energy conversion. • Give examples of energy conversions for the different forms of energy. • Explain how energy conversions make energy useful. • Explain the role of machines in energy conversions. OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P37 Energy Conversions in a Roller Coaster* CD Science Tutor TE Demonstration Where Does the Energy Go?, p. 254 g TE Activity Chemical Energy to Thermal Energy, p. 255 g SE School-to-Home Activity Energy Conversions, p. 256 g LB Labs You Can Eat Power-Packed Peanuts* b PACING • 45 min pp. 254–257 Section 3 Conservation of Energy • Explain how energy is conserved within a closed system. • Explain the law of conservation of energy. • Give examples of how thermal energy is always a result of energy conversion. • Explain why perpetual motion is impossible. OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P38 Formation of Fossil Fuels* TR LINK TO LINK TO EARTH SCIENCE EARTH SCIENCE E11 Porous Rocks as Reservoirs for Fossil Fuels* CD Interactive Explorations CD-ROM The Generation Gap g CD Science Tutor TE Activity Sources of Energy, p. 258 g TE Connection Activity Math, p. 259 g TE Connection Activity History, p. 259 g TE Activity The Ozone Layer, p. 261 a LB Labs You Can Eat Now You’re Cooking!* b LB Long-Term Projects & Research Ideas Great Balls of Fire* a SE Science in Action Math, Social Studies, and Language Arts Activities, pp. 270–271 g LB Calculator-Based Labs Solar Homes* a PACING • 45 min pp. 258–263 Section 4 Energy Resources • Name several energy resources. • Explain how the sun is the source of most energy on Earth. • Evaluate the advantages and disadvantages of using various energy resources. OSP Parent Letter ■ CD Student Edition on CD-ROM CD Guided Reading Audio CD ■ TR Chapter Starter Transparency* VID Brain Food Video Quiz SE Start-up Activity, p. 239 g pp. 238–247 PACING • 90 min CRF Vocabulary Activity* g SE Chapter Review, pp. 266–267 g CRF Chapter Review* ■ g CRF Chapter Tests A* ■ g , B* a , C* s SE Standardized Test Preparation, pp. 268–269 g CRF Standardized Test Preparation* g CRF Performance-Based Assessment* g OSP Test Generator, Test Item Listing CHAPTER REVIEW, ASSESSMENT, AND STANDARDIZED TEST PREPARATION PACING • 90 min Online and Technology Resources Visit go.hrw.com for access to Holt Online Learning, or enter the keyword HP7 Home for a variety of free online resources. This CD-ROM package includes: • Lab Materials QuickList Software • Holt Calendar Planner • Customizable Lesson Plans • Printable Worksheets • ExamView ® Test Generator • Interactive Teacher’s Edition • Holt PuzzlePro ® • Holt PowerPoint ® Resources
Transcript
OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES
Compression guide:To shorten instructionbecause of time limitations,omit Section 4.
9 Energy and Energy ResourcesChapter Planning Guide
Chapter Opener
237A Chapter 9 • Energy and Energy Resources
OSP Lesson Plans (also in print)TR Bellringer Transparency*
TR P32 Energy and Work* TR P33 Thermal Energy in Water*CRF SciLinks Activity*g SE Internet Activity, p. 244gCD Science Tutor
TE Demonstration Forms of Energy, p. 240g TE Demonstration All Wound Up!, p. 241g TE Activity El Niño, p. 244a SE Quick Lab Hear That Energy!, p. 245g
CRF Datasheet for Quick Lab*LB Whiz-Bang Demonstrations Wrong-Way Roller?*bLB Calculator-Based Labs Power of the Sun*a
Section 1 What Is Energy?• Explain the relationship between energy and work.• Compare kinetic and potential energy.• Describe the different forms of energy.
OSP Lesson Plans (also in print)TR Bellringer Transparency*
TR P34 Potential Energy and KineticEnergy*
TR P35 From Light Energy to ChemicalEnergy*
TR LINK TOLINK TO LIFE SCIENCELIFE SCIENCE L46Photosynthesis*
TR P36 Energy Conversions in a Bicycle*VID Lab Videos for Physical ScienceCD Science Tutor
TE Connection Activity Environmental Science,p. 250g
SE Skills Practice Lab Finding Energy, p. 264gCRF Datasheet for Chapter Lab* SE Skills Practice Lab Energy of a Pendulum,
p. 723gCRF Datasheet for LabBook*
LB Whiz-Bang Demonstrations Pendulum Peril*b
PACING • 90 min pp. 248–253Section 2 Energy Conversions• Describe an energy conversion.• Give examples of energy conversions for the different
forms of energy.• Explain how energy conversions make energy useful.• Explain the role of machines in energy conversions.
OSP Lesson Plans (also in print)TR Bellringer Transparency*
TR P37 Energy Conversions in a RollerCoaster*
CD Science Tutor
TE Demonstration Where Does the Energy Go?,p. 254g
TE Activity Chemical Energy to Thermal Energy,p. 255g
SE School-to-Home Activity Energy Conversions,p. 256g
LB Labs You Can Eat Power-Packed Peanuts*b
PACING • 45 min pp. 254–257Section 3 Conservation of Energy• Explain how energy is conserved within a closed
system.• Explain the law of conservation of energy.• Give examples of how thermal energy is always a
result of energy conversion.• Explain why perpetual motion is impossible.
OSP Lesson Plans (also in print)TR Bellringer Transparency*
TR P38 Formation of Fossil Fuels* TR LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E11 Porous
Rocks as Reservoirs for Fossil Fuels* CD Interactive Explorations CD-ROM
The Generation GapgCD Science Tutor
TE Activity Sources of Energy, p. 258g TE Connection Activity Math, p. 259g TE Connection Activity History, p. 259g TE Activity The Ozone Layer, p. 261aLB Labs You Can Eat Now You’re Cooking!*bLB Long-Term Projects & Research Ideas Great Balls of
Fire*a SE Science in Action Math, Social Studies, and Language
Arts Activities, pp. 270–271gLB Calculator-Based Labs Solar Homes*a
PACING • 45 min pp. 258–263Section 4 Energy Resources• Name several energy resources.• Explain how the sun is the source of most energy
on Earth.• Evaluate the advantages and disadvantages of using
various energy resources.
OSP Parent Letter ■
CD Student Edition on CD-ROM CD Guided Reading Audio CD ■
TR Chapter Starter Transparency*VID Brain Food Video Quiz
SE Start-up Activity, p. 239gpp. 238–247PACING • 90 min
CRF Vocabulary Activity*g SE Chapter Review, pp. 266–267g
CRF Chapter Review* ■g
CRF Chapter Tests A* ■ g, B*a, C*s SE Standardized Test Preparation, pp. 268–269g
CRF Standardized Test Preparation*gCRF Performance-Based Assessment*gOSP Test Generator, Test Item Listing
CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION
PACING • 90 min
Online and Technology Resources
Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HP7 Homefor a variety of freeonline resources.
SE Reading Strategy Discussion, p. 240g SE Math Focus Kinetic Energy, p. 241g SE Math Focus Gravitational Potential Energy, p. 242g TE Support for English Language Learners, p. 245
SE Reading Checks, pp. 240, 243, 245, 246g TE Reteaching, p. 246b TE Quiz, p. 246g TE Alternative Assessment, p. 246g SE Section Review,* p. 247 ■g
SE Reading Strategy Brainstorming, p. 248g TE Support for English Language Learners, p. 251 MS Math Skills for Science A Bicycle Trip*gCRF Reinforcement Worksheet See What I Saw; Energetic
Cooking*b
SE Reading Checks, pp. 249, 250, 252g TE Reteaching, p. 252b TE Quiz, p. 252g TE Alternative Assessment, p. 252g SE Section Review,* p. 253 ■g
CRF Section Quiz* ■g
UCP 3; PS 3a, 3d, 3f; ChapterLab: UCP 2; SAI 1, 2; PS 3a;LabBook: SAI 1, 2; PS 3a
SE Reading Strategy Reading Organizer, p. 258g TE Inclusion Strategies, p. 260 TE Support for English Language Learners, p. 261
CRF Critical Thinking The Armchair Enviro-Challenge*a
SE Reading Checks, pp. 258, 260, 262g TE Reteaching, p. 262b TE Quiz, p. 262g TE Alternative Assessment, p. 262g SE Section Review,* p. 263 ■g
CRF Section Quiz* ■ g
SPSP 2; PS 3a, 3e, 3f
SE Pre-Reading Activity, p. 238gOSP Science Puzzlers, Twisters & Teasersg
National ScienceEducation Standards
PS 3a; SAI 1, 2
CRF Chapter Resource File SS Science Skills Worksheets IT Interactive TextbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner
SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish
KEY
Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.
www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HP5CS09T.
• Lab Videos demonstratethe chapter lab.
• Brain Food Video Quizzeshelp students review thechapter material.
ClassroomVideos
Holt Lab GeneratorCD-ROM
Search for any lab by topic, standard,difficulty level, or time. Edit any labto fit your needs, or create your ownlabs. Use the Lab Materials QuickListsoftware to customize your labmaterials list.
1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2
2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2
3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1
4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2
5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2
6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2
7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2
8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2
9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2
10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2
TEACHER RESOURCE PAGE
Lesson Plan
Section: Waves
PacingRegular Schedule: with lab(s): 2 days without lab(s): 2 days
Block Schedule: with lab(s): 1 1/2 days without lab(s): 1 day
Objectives1. Relate the seven properties of life to a living organism.
2. Describe seven themes that can help you to organize what you learn aboutbiology.
3. Identify the tiny structures that make up all living organisms.
4. Differentiate between reproduction and heredity and between metabolismand homeostasis.
National Science Education Standards CoveredLSInter6: Cells have particular structures that underlie their functions.
LSMat1: Most cell functions involve chemical reactions.
LSBeh1:Cells store and use information to guide their functions.
UCP1:Cell functions are regulated.
SI1: Cells can differentiate and form complete multicellular organisms.
PS1: Species evolve over time.
ESS1: The great diversity of organisms is the result of more than 3.5 billion yearsof evolution.
ESS2: Natural selection and its evolutionary consequences provide a scientificexplanation for the fossil record of ancient life forms as well as for the strikingmolecular similarities observed among the diverse species of living organisms.
ST1: The millions of different species of plants, animals, and microorganismsthat live on Earth today are related by descent from common ancestors.
ST2: The energy for life primarily comes from the sun.
SPSP1: The complexity and organization of organisms accommodates the needfor obtaining, transforming, transporting, releasing, and eliminating the matterand energy used to sustain the organism.
SPSP6: As matter and energy flows through different levels of organization ofliving systems—cells, organs, communities—and between living systems and thephysical environment, chemical elements are recombined in different ways.
HNS1: Organisms have behavioral responses to internal changes and to externalstimuli.
This CD-ROM includes all of the resources shown here and the following time-saving tools:
• Lab Materials QuickList Software
• Customizable lesson plans
• Holt Calendar Planner
• The powerful ExamView ® Test Generator
Chapter Resources
Dear Parent,
Your son's or daughter's science class will soon begin exploring the chapter entitled “The
World of Physical Science.” In this chapter, students will learn about how the scientific
method applies to the world of physical science and the role of physical science in the
world. By the end of the chapter, students should demonstrate a clear understanding of the
chapter’s main ideas and be able to discuss the following topics:
1. physical science as the study of energy and matter (Section 1)
2. the role of physical science in the world around them (Section 1)
3. careers that rely on physical science (Section 1)
4. the steps used in the scientific method (Section 2)
5. examples of technology (Section 2)
6. how the scientific method is used to answer questions and solve problems (Section 2)
7. how our knowledge of science changes over time (Section 2)
8. how models represent real objects or systems (Section 3)
9. examples of different ways models are used in science (Section 3)
10. the importance of the International System of Units (Section 4)
11. the appropriate units to use for particular measurements (Section 4)
12. how area and density are derived quantities (Section 4)
Questions to Ask Along the Way
You can help your son or daughter learn about these topics by asking interesting questions
such as the following:
• What are some surprising careers that use physical science?
• What is a characteristic of a good hypothesis?
• When is it a good idea to use a model?
• Why do Americans measure things in terms of inches and yards instead of centimeters
Not all of the cars’ potential energy (PE) is converted into kinetic energy (KE) as the cars go down the first hill. In addition, not all of the cars’ kinetic energy is converted into potential energy as the cars go up the second hill. Some of it is changed into thermal energy because of friction.
PE is greatest at the top of the first hill.
KE at the bottom of the first hill is less than the PE at the top was.
PE at the top of the sec-ond hill is less than KEand PE from the first hill.
a
c
b
Chapter: Energy Resources
Strange butTrue!
Energy and Energy Resources CHAPTER STARTER
Vast treasures are buried at sea. No, they’renot gold doubloons—they’re gas hydrates(HIE DRAYTS), energy resources that maybecome more important in the future.
Gas hydrates are icy formations of waterand methane, the main component of natural gas. The methane in hydrates is produced by bacteria that help decomposeorganic material in the ocean. Hydratesform at depths of 300–800 m.
Gas-hydrate deposits are found underthe Arctic permafrost and in marine sedi-ments. Off the coasts of North Carolina andSouth Carolina, scientists have found twodeposits that may contain 37 trillion cubicmeters of methane gas. That’s 70 times theamount of natural gas consumed by theUnited States in 1 year!
When brought to temperatures of around15°C, the snowball-like hydrates fizz like effer-vescent tablets. And holding a flame near ahydrate ignites the evaporating methane,making the gas hydrate look like a burningice cube. In both instances, the energyreleased could be used to drive machineryor generate electrical energy.
Unfortunately, mining gas hydrates isexpensive. But as more research isdone, gas hydrates may play abigger role in the wayenergy is used every day.In this chapter, you’lllearn about energy,energy conversions, andenergy resources.
Because of the methane locked inside theseicy formations, gas hydrates may become avery valuable energy resource.
Section: What Is Energy?Finish the following phrase:
“Energy is the ability to ____.”
Write your completed phrase in your science
journal. We often use the words energy and power
synonymously, but they have specific meanings.What is the distinction between energy and power?
Section: Energy ConversionsWhat do the following objects have in common:a plant, a Bunsen burner, a pendulum. Can you think ofthree more objects that have the same common link?
Record your guesses in your science journal.
can be a combination of
which is theenergy of
which depends on
which is theenergy of
may beconverted by
speed
Energy and Energy Resources CONCEPT MAPPING TRANSPARENCY
Use the following terms to complete the concept map below:potential energy, position, mechanical energy, motion, kinetic energy,mass, machines
SAMPLE SAMPLE SAMPLE
Meeting Individual Needs
Review and Assessments
Labs and Activities
DIRECTED READING A VOCABULARY ACTIVITY REINFORCEMENT
STANDARDIZED TEST PREPARATIONCHAPTER TEST BCHAPTER REVIEWSECTION QUIZ
SCILINKS ACTIVITY
MARINE ECOSYSTEMS
Go to www.scilinks.com. To find links relatedto marine ecosystems, type in the keywordHL5490. Then, use the links to answer thefollowing questions about marine ecosys-tems.
1. What percentage of the Earth’s surface iscovered by water?
2. What percentage of the Earth’s water is found in the oceans?
3. What is the largest animal on Earth?
4. Describe an ocean animal.
Name Class Date
SciLinks ActivityActivity
Developed and maintained by theNational Science Teachers Association
Getting the Dirt on the SoilAfter you finish reading Chapter: [Unique Title], try this puzzle! Use the clues belowto unscramble the vocabulary words. Write your answer in the space provided.
1. the breakdown of rock intosmaller and smaller pieces:AWERIGNETH
2. layer of rock lying beneath soil:CROKDEB
3. type of crop that is plantedbetween harvests to reduce soilerosion: CROVE
4. action of rocks and sedimentscraping against each other andwearing away exposed surfaces:SABRONIA
5. a mixture of small mineral frag-ments and organic matter: LISO
6. rock that is a source of soil:PRATEN CORK
7. type of reaction that occurs whenoxygen combines with iron toform rust: oxidation
8. type of weathering caused byphysical means: CLEMANIACH
9. the chemical breakdown of rocksand minerals into new substances: CAMILCHETHEARIGWEN
10. layers of soil, to a geologist:SNORHIZO
11. the uppermost layer of soil:SPOTOIL
12. process in which rainwater car-ries dissolved substances fromthe uppermost layers of soil to thebottom layers: HELANCIG
13. small particles of decayed plantand animal material in soil:MUUSH
14. the process in which wind, water,or ice moves soil from one location to another: ROOSINE
15. the methods humans use to takecare of soil:OSIL VASETONRICON
LONG-TERM PROJECTS & RESEARCH IDEAS LABS YOU CAN EAT
1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.
2. What is unusual about the way that Proteus moves through the water?
MATTER + AIR ➔ PHYSICAL SCIENCE
3. What do air, a ball, and a cheetah have in common?
4. What is one question you will answer as you explore physical science?
5. Chemistry and physics are both fields of . Chemists
study the different forms of and how they interact.
and how it affects are
studied in physics.
Identify the field of physical science to which each of the following descriptionsbelongs by writing physics or chemistry in the space provided.
_______________________ 6. how a compass works
_______________________ 7. why water boils at 100°C
_______________________ 8. how chlorine and sodium combine to form table salt
_______________________ 9. why you move to the right when the car you are inturns left
Directed Reading A
Name Class Date
Skills Worksheet
DIRECTED READING B
Section: ExploringTHAT’S SCIENCE!
1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.
2. What is unusual about the way that Proteus moves through the water?
MATTER + AIR ➔ PHYSICAL SCIENCE
3. What do air, a ball, and a cheetah have in common?
Directed Reading B
Name Class Date
Skills Worksheet
Section: UniqueVOCABULARY
In your own words, write a definition of the following term in the space provided.
1. scientific method
2. technology
3. observation
Name Class Date
Vocabulary & NotesSkills Worksheet
Name Class Date
ReinforcementSkills Worksheet
The Plane TruthComplete this worksheet after you finish reading the Section: [Unique SectionTitle]
You plan to enter a paper airplane contest sponsoredby Talkin’ Physical Science magazine. The personwhose airplane flies the farthest wins a lifetime sub-scription to the magazine! The week before the con-test, you watch an airplane landing at a nearbyairport. You notice that the wings of the airplane haveflaps, as shown in the illustration at right. The paperairplanes you’ve been testing do not have wing flaps.What question would you ask yourself based on these observations? Write yourquestion in the space below for “State the problem.” Then tell how you could usethe other steps in the scientific method to investigate the problem.
Dear Mr. Burns,I’ve got this great idea for a new product called the BlissHeater. It’s a portable, solar-powered space heater. The heater’s design includes these features:•T
he heater will be as longas an adult’s arm and aswide as a
packing box.
•T
he heater will have aglass top set at an angleto catch the sun’s rays.
•T
he inside of the heaterwill be dark colored toabsorb solar heat.If you think my idea will work, I will make the Bliss
Heaters right away without wasting time and money on test-ing and making models. Please write back soon with youropinion.
SECTION REVIEW
Section: UniqueKEY TERMS
1. What do paleontologist study?
2. How does a trace fossil differ from petrified wood?
In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.
______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.
______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.
______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.
______ 4. Which of the following does NOT control surface currents?a. global wind c. Coriolis effectb. tides d. continental deflections
______ 5. Whitecaps break a. in the surf. c. in the open ocean.b. in the breaker zone. d. as their wavelength increases.
______ 6. Most ocean waves are formed by a . earthquakes. c. landsides.b. wind. d. impacts by cosmic bodies.
______ 7. Which factor controls surface currents? a. global winds c. continental deflectionb. the Coriolis effect d. all of the above
______ 8. Streamlike movments of ocean water far below the surface arecalleda. jet currents c. surface currents.b. Coriolis currents. d. deep currents.
______ 9. When the sunlit part of the moon that can be seen from Earthgrows larger, it is a. waxing. c. in the new moon phase.b. waning. d. in the full moon phase.
______10. The Milky Way is thought to be a. an elliptical galaxy. c. a spiral galaxy.
Read the passages below. Then, read each question that follows the passage.Decide which is the best answer to each question.
Passage 1 adventurous summer camp in the world. Billy can’twait to head for the outdoors. Billy checked the recommendedsupply list: light, summer clothes; sunscreen; rain gear; heavy,down-filled jacket; ski mask; and thick gloves. Wait a minute! Billythought he was traveling to only one destination, so why does heneed to bring such a wide variety of clothes? On further investiga-tion, Billy learns that the brochure advertises the opportunity to“climb the biomes of the world in just three days.” The destinationis Africa’s tallest mountain, Kilimanjaro.
______ 1. The word destination in this passage means A camp B vacation.C place. D mountain.
______ 2. Which of the following is a FACT in the passage? F People ski on Kilimanjaro.G Kilimanjaro is Africa’s tallest mountain.H It rains a lot on Kilimanjaro.J The summers are cold on Kilimanjaro.
______ 3. Billy wondered if the camp was advertising only one destination afterhe read the brochure, which said thatA the camp was the most adventurous summer camp in the world. B he would need light, summer clothes and sunscreen.C he would need light, summer clothes and a heavy, down-filled
jacket.D the summers are cold on Kilimanjaro.
Name Class Date
Standardized Test PreparationAssessment
PERFORMANCE-BASEDASSESSMENT
OBJECTIVEDetermine which factors cause some sugar shapes to break down faster than others.
KNOW THE SCORE!As you work through the activity, keep in mind that you will be earning a gradefor the following:
• how you form and test the hypothesis (30%)
• the quality of your analysis (40%)
• the clarity of your conclusions (30%)
ASK A QUESTIONSWhy do some sugar shapes erode more rapidly than others?
2. Describe the characteristics of a savanna and a desert.
3. Identify the relationship between tundra and permafrost.
4. Compare the open-water zone and the deep-water zone.
5. Use each of the following terms in an original sentence: plankton, littoralzone, and estuary.
6. Describe how marshes and swamps differ.
Name Class Date
Chapter ReviewSkills Worksheet
SCIENCE PUZZLERS, TWISTERS & TEASERS
CHAPTER TEST A
[UniqueMULTIPLE CHOICE
In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.
______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.
______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.
______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.
______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect
Name Class Date
Chapter Test AAssessment
CHAPTER TEST C
[UniqueMULTIPLE CHOICE
In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.
______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.
______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.
______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.
______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect
Name Class Date
Chapter Test CAssessment
TEACHER-LED DEMONSTRATION
DEMO
50
Purpose
Students observe the movement of a water-balloon pendulum to understandconversions between potential and kinetic energy.
Time Required
10–15 minutes
What to Do
1. Attach the string to the ceiling. Fill theballoon with water and attach it se-curely to the free end of the string.
2. Adjust the length of the string so thatthe balloon just reaches your nosewhen you stand with your back againsta wall. Securely tighten all of the knots.
3. Stand against the wall and hold the wa-ter balloon a few centimeters from yourface. Ask students what they expect tohappen when you release the balloon.(Expected answer: It will swing forwardand then swing back and hit you in theface. You will get soaked!)
4. Now, with feigned anxiety, release theballoon and wait for it to swing back.Do not push the balloon or move yourhead!
Explanation
When the balloon is held in place, there isgravitational potential energy associatedwith its position. When the balloon is re-leased, some of this potential energy isgradually converted into kinetic energy. Atthe midpoint of the swing, the kinetic en-ergy is at a maximum, so the balloon isswinging at its fastest. After the midpointof the swing, the kinetic energy is gradu-ally converted back into potential energy.In the absence of friction, this cycle wouldcontinue indefinitely, and the balloon
continued...
Pendulum Peril
MATERIALS
• tap water• balloon• nylon string about 3 m long
Donna NorwoodMonroe Middle SchoolMonroe, North Carolina
TEACHER PREP
CONCEPT LEVEL
CLEAN UP
E A S Y H A R D
Lab Ratings
Chapter 9 • Chapter Resources 237D
LABS YOU CAN EAT
STUDENT WORKSHEET
LAB
20
Name Date Class
The world runs on many different kinds of fuel—cars runon gas, and our homes are often heated by oil. But did youknow you can burn a peanut to heat water? A peanut maybe small, but this amazing underground fruit can packquite a punch! Let’s take a look at just how much energywe can find in a peanut.
Power-Packed Peanuts
Ask a QuestionHow do you measure the amount of energy in apeanut?
Conduct an Experiment1. Set up the apparatus as shown below. Be sure to place the
thermometer so that the tip is in the can but does not touchthe bottom of the can. The can should be 2.5–5 cm from thetop of the peanut.
2. Pour 100 mL of water into the can, and record the watert t i th T t Ch t 97
MATERIALS
• alcohol thermometer• support stand with
ring clamp• wire gauze• clean, empty can• shelled peanut• paper clip• cork covered in
aluminum foil• metric ruler• 125 mL graduated
For a preview of available worksheets covering math and science skills, see pages T26–T33. All of these resources are also on the One-Stop Planner®.
When They Were in the 8th Grade (Tall Tales)1. When they were in the 8th grade, some famous scientists and
inventors had some strange ideas about various types of energy.From the clues, identify the types of energy and write them in theblanks.a. Sir Isaac Newton wanted to invent an air conditioner for birds.
He constructed a wind tunnel and pointed it at the apple treewhere his favorite birds perched themselves. As a result, the
energy of the apples was con-
verted into energy and they fellon Newton’s head. And now we have a theory of gravity.
b. Dennis Oppenheimer wanted to make water lighter so that hispack would weigh less when he went hiking. He decided to dothis by splitting the hydrogen atom (of which there are two pereach water molecule) in half. The result was a large explosion
Name _______________________________________________ Date ________________ Class______________
SCIENCE PUZZLERS, TWISTERS & TEASERS9
Energy and Energy Resources
CHAPTER
While sitting on her front porch during a thunderstorm in 1985, a Massachusettswoman saw a “white ball of fire” rolling up her street. It was sparking and crack-ling and sending out small fingers of lightning to the cars and telephone poles itpassed. The ball, about a meter in diameter, split into three pieces, then into six,then joined back to three, and then back to its original size before disappearing.The power in the neighborhood went out for 2 hours.
Seem strange? Most people have witnessed lightning bolts in thunderstorms, butfew have ever seen ball lightning. Although rare, it has been noted by individualsall the way back to the ancient Greeks. Ball lightning has been reported to enterairplanes and even to “chase” a flight attendant around the cabin! The nature ofball lightning is not well understood, ranking it among the more interestingscientific mysteries of the day.
1�2
A Striking Idea1. Using the library and the Internet, find out more about
ball lightning. How often is it reported? What are sometheories to explain it? Are there any myths about balllightning? Write a report in the form of a scientific maga-zine article. If possible, include quotes from firsthandreports of its sightings.
Another Research Idea2. Where will the energy your children use come from? Though
we rely on fossil fuels for the majority of our energy today,their limited supply and environmental impact force us tokeep seeking new ways to generate energy. What are themost promising alternative energy sources being exploredtoday? Choose one technology and create a Web page orreport about it. Include its advantages and disadvantages,its potential for large-scale use, and a brief history of itsdevelopment.
Long-Term Project Idea3. Is your refrigerator taking money from you? Is your
dishwasher sapping precious energy? Some appliancesuse more energy than others to do the same amount of
work. Visit an appliance store, choose one type ofappliance, and record the information shown on theyellow Energy Guide tag (the estimated cost of usingthat appliance for one year) for each model of thatappliance. Make a chart listing several appliances in onecategory from highest to lowest Energy Guide rating.What features might lower the Energy Guide rating forthe appliance you chose? Prepare a report with your
findings.
Name ___________________________________________________ Date _________________ Class _____________
Reaction to StressQuick Lab DATASHEET FOR QUICK LAB
BackgroundThe graph below illustrates changes that occur in the membrane potential of aneuron during an action potential. Use the graph to answer the followingquestions. Refer to Figure 3 as needed.
Analysis1. Determine about how long an action potential lasts.
2. State whether voltage-gated sodium, chanels are open or closed at point A.
3. State whether voltage-gated potassium channels are open or closed atpoint B.
4. Critical Thinking Recognizing Relationships What causes the menberneotential to become less negative at point A?
5. Critical Thinking Recognizing Relationships What causes the membranepotential to become more negative at point B?
Have you ever walked barefoot across a black surface on a hotsummer day? Ouch! The black surface gets much hotterthan the air around you because the surface is an ef-fective absorber of the sun’s rays, or solar energy. Thepavement absorbs solar energy and stores it as heat.
Solar energy can be used to cook other things be-sides your feet. In this project, you will be part of ateam that will compete to build the best solar energy col-lector for cooking a hot dog. The winning cooker will be the firstone to raise the internal temperature of a hot dog to 100°C. The planningand construction of the cooker is up to you, so put your hot ideas to work!
Now You’re Cooking!
Ask a QuestionWhat kind of solar cooker will most effectivelyheat a hot dog to 100°C?
BrainstormAs a team, determine how you will solve the above problem.Ask yourself questions such as the following:
• What size and shape should your cooker be in order to col-lect sunlight most effectively?
• What is the best way to trap heat in the cooker?
• Should you include a lid in the design?
• How will different materials, colors, thicknesses, and texturesaffect your cooker’s performance?
• Will you need to adjust your cooker as the position of thesun changes?
• Will your cooker work well in partial sunlight?
Form a Hypothesis Based on your discussion, record a hypothesis in yourScienceLog about what kind of solar cooker will best accom-plish your goal.
MATERIALS
• boxes with removabletops
• reflective emergencyblanket
• oven cooking bag• aluminum foil• newspaper• white glue• scissors• masking tape• pen or marker• metric ruler• 2 oven mitts• cooking thermometer• 2 hot dogs or other
food items• hot dog buns,
mustard, relish, etc.
CALCULATOR-BASED LABS
Energy from the sun or any light source travels as light (orradiant) energy. This energy radiates in every direction.How much radiant energy an object receives depends onhow close that object is to the radiant energy source. Asyou move farther from the source, the amount of energythat is received decreases. When light energy is absorbed byan object it is converted into heat energy.
Power is the rate at which one form of energy is con-verted into another in a given amount of time. It is meas-ured in watts (W). Because power is related to distance,nearby objects can be used to measure the power of far-away objects. For example, the rate at which the electric light bulb you will usein this experiment changes electric energy into light or heat energy is 100 W.
Procedure
1. Put on your protective gloves. To set up the experiment,gently shape the piece of aluminum around the pencil sothat it attaches to the middle and has two wings, one onith id f th il
STUDENT WORKSHEET8
Power of the Sun
LAB
Name _______________________________________________ Date ________________ Class______________
The materials listed on the student page are enough for a group of 4–5 students.Large, dried beans of any kind will work well in this exercise.
SAFETY CAUTION
Remind students to review all safety cautions and icons before beginning this labactivity.
Using Scientific MethodsSkills Practice Lab DATASHEET FOR CHAPTER LAB
TEACHER RESOURCE PAGE
1 2 3 4Easy Hard
Jason MarshMontevideo High
and Country School
SAMPLE
DATASHEETS FORLABBOOK
Teacher’s NotesTIME REQUIRED
One 45-minute class period.
Does It All Add Up?Skills Practice Lab DATASHEET FOR LABBOOK LAB
TEACHER RESOURCE PAGE
Jason MarshMontevideo High
SAMPLE
ENG-P0
This Chapter Enrichment provides relevant and
interesting information to expand and enhance
your presentation of the chapter material.
What Is Energy?Energy• Energy is the ability to do work. Work occurs when a
force causes an object to move in the direction of the force. Both energy and work are expressed in units called joules (J), named for James Prescott Joule. One joule is the amount of work done when a force of 1 N acts through a distance of 1 m (1 J � 1 N � 1 m).
James Prescott Joule• The English scientist James Prescott Joule (1818–1889)
was the son of a wealthy brewery owner. Joule used his financial resources to conduct research in a variety of areas. Joule worked to improve the efficiencyof electric motors so that they could be used to replace steam engines. His research was some of the first to show the connec-tion between thermal energy and other formsof energy.
Is That a Fact!◆ The countries of North America consume about 30%
of the total world energy output. The countries of the former Soviet Union consume about 11% to 15%.
Energy ConversionsKinetic and Potential Energy• The conversion of potential energy to kinetic
energy (and vice versa) is classically demonstrated by a bouncing ball.
• A moving object has kinetic energy. The amount of kinetic energy is proportional to the mass of the object and the square of the speed of the object.
Gravitational Potential Energy• An object that has been lifted from its position on
Earth’s surface has gravitational potential energy. If you drop the object and nothing is in its way, the gravitational potential energy will immediately begin to change into kinetic energy as the object accelerates toward Earth.
Light Energy to Chemical Energy• Plants use photosynthesis to make molecules
that have high chemical energy, such as sugars, from water and carbon dioxide, which have low chemical energy. To increase the amount of chemical energy, light energy is converted to chemical energy, and ATP is formed. In a separate series of reactions, plants convert sugars to starches.
• When you eat plants, your digestive system transforms the high-energy sugars and starches into smaller, lower-energy molecules. The chemical energy in the sugars and starches fuels your body functions and movements and pro vides the thermal energy that keeps your body temperature constant.
Chapter Enrichment9
237E Chapter 9 • Energy and Energy Resources
SciLinks is maintained by the National Science Teachers Associationto provide you and your students with interesting, up-to-date links thatwill enrich your classroom presentation of the chapter.
Developed and maintained by theNational Science Teachers Association
Visit www.scilinks.org and enter the SciLinks code for moreinformation about the topic listed.
Chemical Energy to Electrical Energy• Batteries consist of cells. A cell converts chemical
energy into electrical energy. A cell has two electrodesand an electrolyte. Between the electrodes are positiveand negative ions. In positively charged ions, thereare fewer electrons than protons, and in negativelycharged ions, there are more electrons than protons.When a circuit is completed, the electrodes react withthe electrolyte. In this reaction, electrons leave one ofthe electrodes and build up on the other. Work is donein separating the charges, and that work is stored inthe battery as electrical potential energy.
• Whenever the electrodes of the battery are connectedwith a wire, work is done on the electrons in the wireas charges flow from the negative electrode of thebattery to the positive electrode.
Conservation of EnergyThe Law of Conservation of Energy• In the presence of friction, mechanical energy (KE �
PE) is not conserved. But mechanical energy does nottake into account the other objects and conversionswithin a closed system. Total energy is always con-served even if mechanical energy is not.
Is That a Fact!◆ The British Patent Office does not accept applications
for perpetual motion machines. Such machines wouldviolate the laws of physics and are thereforeconsidered impossible.
◆ The United States Patent Office accepts about100 applications for perpetual motion machinesevery year.
Energy ResourcesFossil Fuels• Fossil fuels take hundreds of thousands—or even
millions—of years to form.
• Coal is formed from plant material that iscompressed in swamps.
• Petroleum and natural gas form from theremains of dead organisms.
Energy Alternatives• Energy sources can be found in nature in a variety
of forms. Wind energy, tidal energy, hydroelectricenergy, and solar energy are alternatives to thenonrenewable fossil fuels used today.
• Although the sun is technically a limited energysource, it still has approximately 5 billion yearsleft in its life span. In the time frame of humanexperience, the sun is considered a limitlesssource of energy.
For background information about teaching strategies and
issues, refer to the Professional Reference for Teachers.
Topic: What Is Energy?SciLinks code: HSM1660
Topic: Forms of EnergySciLinks code: HSM0612
Topic: Energy ConversionsSciLinks code: HSM0511
Topic: Law of Conservation ofEnergy
SciLinks code: HSM0856
Topic: Energy ResourcesSciLinks code: HSM0515
Chapter 9 • Chapter Enrichment 237F
National Science Education Standards
The following codes indicate the National Science EducationStandards that correlate to this chapter. The full text of thestandards is at the front of the book.
Chapter OpenerSAI 1, 2; PS 3a
Section 1 What Is Energy?SAI 1; PS 3a, 3e, 3f
Section 2 Energy ConversionsUCP 3; PS 3a, 3d, 3f; LabBook: SAI 1, 2; PS 3a
Section 3 Conservation of EnergyUCP 1, 3; ST 2; PS 3a
Section 4 Energy ResourcesSPSP 2; PS 3a, 3e, 3f
Chapter LabUCP 2; SAI 1; PS 3a
Chapter ReviewSAI 1; PS 3a
Science in ActionSAI 2; ST2; SPSP 5; HNS 1; PS 3a
OverviewTell students that this chapterwill help them recognize energyin its different forms, learn howenergy is measured, and learnhow energy can be convertedfrom one form to another.
Assessing PriorKnowledgeStudents should be familiarwith the following topics:
• matter
• motion
• forces
IdentifyingMisconceptionsStudents may believe either thatenergy is associated only withinanimate objects or only withhumans or that energy is a fluid,ingredient, or fuel. Many stu-dents believe that energy trans-formations involve only oneform of energy at a time.Transformations such as thetransformation from motion toheat are especially hard to visu-alize. The idea of energy conser-vation is counter-intuitive tomany students. Students ofteninterpret “Energy is neither cre-ated nor destroyed” to mean thatenergy is stored up in a systemand often is released in its origi-nal form. Teaching energy (heat)dissipation ideas and energyconservation at the same timemay help alleviate confusion. Standards Correlations
9
238 Chapter 9 • Energy and Energy Resources
Energy and Energy Resources
About the
Imagine that you’re a driver in this race. Yourcar needs a lot of energy to fi nish. So, itprobably needs a lot of gasoline, right? No, itjust needs a lot of sunshine! This car runs onsolar energy. Solar energy is one of the manyforms of energy. Energy is needed to drive acar, turn on a light bulb, play sports, and walkto school. Energy is always being changedinto different forms for different uses.
Layered Book Beforeyou read the chapter, createthe FoldNote entitled “Lay-
ered Book” described in the Study Skillssection of the Appendix. Label the tabs ofthe layered book with “Types of energy,”“Energy conversions,” “Conservation ofenergy,” and “Energy resources.” As youread the chapter, write information youlearn about eachcategory under theappropriate tab.
SECTION
Energy can be changed fromone form into another form,but energy cannot be createdor destroyed.
9
1 What Is Energy? . . . . . . . . . . . . 240
2 Energy Conversions . . . . . . . . . 248
3 Conservation of Energy . . . . . 254
4 Energy Resources. . . . . . . . . . . 258
START-UPEnergy Swings! In this activity, you’ll observe a moving pendulum to learn about energy.
Procedure1. Make a pendulum by tying a 50 cm long string
around the hook of a 100 g hooked mass.
2. Hold the string with one hand. Pull the mass slightly to the side, and let go of the mass without pushing it. Watch it swing at least 10 times.
3. Record your observations. Note how fast and how high the pendulum swings.
4. Repeat step 2, but pull the mass farther tothe side.
5. Record your observations. Note how fast and how high the pendulum swings.
Analysis1. Does the pendulum have energy? Explain your
answer.
2. What causes the pendulum to move?
3. Do you think the pendulum had energy before you let go of the mass? Explain your answer.
Chapter 9 • Energy and Energy Resources 239
START-UPSTART-UP vvM A T E R I A L S
FOR EACH GROUP• mass, 100 g hooked• string, 50 cm long
Safety Caution: Remind stu-dents to review all safety cau-tions and icons before beginning this activity. Goggles must be worn for this activity.
Answers
1. Accept all reasonable responses. Sample answer: The pendulum has energy because it moves.
2. Accept all reasonable responses. Sample answer: Gravity causes the pendulum to move.
3. Accept all reasonable responses. Sample answer: The pendulum has energy. It is storing the energy that I used to move it. That energy is released when I let go of the pendulum.
Strange butTrue!
Energy and Energy Resources CHAPTER STARTER
Vast treasures are buried at sea. No, they’renot gold doubloons—they’re gas hydrates(HIE DRAYTS), energy resources that maybecome more important in the future.
Gas hydrates are icy formations of waterand methane, the main component of natural gas. The methane in hydrates is produced by bacteria that help decomposeorganic material in the ocean. Hydratesform at depths of 300–800 m.
Gas-hydrate deposits are found underthe Arctic permafrost and in marine sedi-ments. Off the coasts of North Carolina andSouth Carolina, scientists have found twodeposits that may contain 37 trillion cubicmeters of methane gas. That’s 70 times theamount of natural gas consumed by theUnited States in 1 year!
When brought to temperatures of around15°C, the snowball-like hydrates fizz like effer-vescent tablets. And holding a flame near ahydrate ignites the evaporating methane,making the gas hydrate look like a burningice cube. In both instances, the energyreleased could be used to drive machineryor generate electrical energy.
Unfortunately, mining gas hydrates isexpensive. But as more research isdone, gas hydrates may play abigger role in the wayenergy is used every day.In this chapter, you’lllearn about energy,energy conversions, andenergy resources.
Because of the methane locked inside theseicy formations, gas hydrates may become avery valuable energy resource.
Chapter Starter TransparencyUse this transparency to help students begin thinking about energy and energy resources.
CHAPTER RESOURCESTechnology
Transparencies • Chapter Starter Transparency
Student Edition on CD-ROM
Guided Reading Audio CD • English or Spanish
Classroom Videos • Brain Food Video Quiz
Workbooks
Science Puzzlers, Twisters & Teasers • Energy and Energy Resources g
READINGSKILLS
READING STRATEGY
What Is Energy?It’s match point. The crowd is silent. The tennis player tosses the ball into the air and then slams it with her racket. The ball flies toward her opponent, who swings her racket at the ball. THWOOSH!! The ball goes into the net, causing it to shake. Game, set, and match!!
The tennis player needs energy to slam the ball with herracket. The ball also must have energy in order to cause thenet to shake. Energy is around you all of the time. But what,exactly, is energy?
Energy and Work: Working TogetherIn science, energyenergy is the ability to do work. Work is done whena force causes an object to move in the direction of the force.How do energy and work help you play tennis? The tennisplayer in Figure 1 does work on her racket by exerting a forceon it. The racket does work on the ball, and the ball does workon the net. When one object does work on another, energyis transferred from the first object to the second object. Thisenergy allows the second object to do work. So, work is atransfer of energy. Like work, energy is expressed in units ofjoules (J).
✓✓Reading Check What is energy? (See the Appendix for answers to Reading Checks.)
1
Figure 1 The tennis player does work and transfers energy to the racket. With this energy, the racket can then do work on the ball.
energyenergy the capacity to do work
What You Will Learn
Explain the relationship betweenenergy and work.Compare kinetic and potentialenergy.Describe the different forms ofenergy.
Vocabularyenergykinetic energypotential energymechanical energy
Discussion Read this section silently.Write down questions that you haveabout this section. Discuss yourquestions in a small group.
OverviewThis section introduces the con-cept of energy. Students willlearn how kinetic and potentialenergy differ and how theseforms of energy relate tomechanical energy. This sectionalso discusses and compares dif-ferent forms of energy.
BellringerWrite the following on theboard: “Energy is the abilityto ____.” Ask students to thinkabout this sentence and to writein their science journal howthey think it should be com-pleted. Lead a brief discussion tointroduce the concept of energyas the ability to do work.
Demonstration --------------gForms of Energy At the begin-ning of class, strike a match andlet it burn for a few moments.Wind up a windup toy, and letit run. Turn off the lights in theclassroom, and turn on a flash-light. Knock a tennis ball off atable so that the ball bouncesonto the floor. Ask studentsto explain how energy wasinvolved in each event. Leadstudents to conclude that thereare many forms of energy.l Visual Answer to Reading Check
Kinetic EnergyIn tennis, energy is transferred from the racket to the ball. As it flies over the net, the ball has kinetic (ki NET ik) energy. Kinetic energy is the energy of motion. All moving objects have kinetic energy. Like all forms of energy, kinetic energy can be used to do work. For example, kinetic energy allows a hammer to do work on a nail, as shown in Figure 2.
Kinetic Energy Depends on Mass and SpeedAn object’s kinetic energy can be found by the following equation:
The m stands for the object’s mass in kilograms. The v stands for the object’s speed. The faster something is moving, the more kinetic energy it has. Also, the greater the mass of a moving object, the greater its kinetic energy is.
A large car has more kinetic energy than a car that has less mass and that is moving at the same speed does. But as you can see from the equation, speed is squared. So speed has a greater effect on kinetic energy than mass does. For this reason, car crashes are much more dangerous at higher speeds than at lower speeds. A moving car has 4 times the kinetic energy of the same car going half the speed! This is because it’s going twice the speed of the slower car, and 2 squared is 4.
Figure 2 When you swing a hammer, you give it kinetic energy, which does work on the nail.
kinetic energy the energy of an object that is due to the object’s motion
Kinetic Energy What is the kinetic energy of a car that has a mass of 1,200 kg and is moving at a speed of 20 m/s?
Step 1: Write the equation for kinetic energy.
Step 2: Replace m and v with the measure-ments given, and solve.
KE � 240,000 kg•m2/s2 � 240,000 J
Now It’s Your Turn1. What is the kinetic energy of a car that
has a mass of 2,400 kg and is moving at 20 m/s? How does this kinetic energy compare to the kinetic energy of the car in the example given at left?
2. What is the kinetic energy of a 4,000 kg elephant that is running at 2 m/s? at 4 m/s? How do the two kinetic energies compare with one another?
3. What is the kinetic energy of a 2,000 kg bus that is moving at 30 m/s?
4. What is the kinetic energy of a 3,000 kg bus that is moving at 20 m/s?
kinetic energy � 2mv2
KE �mv2
2
KE �1,200 kg � (20 m/s)2
2
KE �1,200 kg � 400 m2/s2
2
KE �480,000 kg•m2/s2
2
Section 1 • What Is Energy? 241
Demonstration --------------gAll Wound Up! Divide the class into small groups, and provide each group with a windup toy. Instruct the groups to wind up their toy and observe what hap-pens. Ask students how many types of energy are involved in this activity. At this point, stu-dents may identify only the kinetic energy of the toy as it moves. Explain that there are at least three other forms of energy here. (chemical energy from food that enables the student to wind up the toy, potential energy in the wound-up spring of the toy, and a small amount of thermal energy as the spring unwinds)
Teacher’s Notes: The equation to determine kinetic energy is
kinetic energy � mv2/2
Speed has a greater impact on kinetic energy than mass does because speed is squared. When mass doubles, kinetic energy doubles. But when speed dou-bles, kinetic energy quadruples. In this equation, the term speed is used instead of velocitybecause energy is a scalar, rather than a vector, quantity. l Kinesthetic
Answers to Math Focus
1. KE � [2,400 kg � (20 m/s)2]/2 �480,000 J. It has twice the kinetic energy of the 1,200 kg car in the example.
2. KE � [4,000 kg � (2 m/s)2]/2 �8,000 JKE � [4,000 kg � (4 m/s)2]/2 �32,000 J
At twice the speed, the ele-phant’s kinetic energy is 4 times what is was before.
3. KE � [2,000 kg � (30 m/s)2]/2 �900,000 J
4. KE � [3,000 kg � (20 m/s)2]/2�600,000 J
The kinetic energy of a snail that has a mass of 5 g and is traveling at 0.014 m/s is 0.00000048 J. By comparison, the kinetic energy of an 18-wheel truck traveling at 26.69 m/s (about 44 mi/h) is 2,200,000 J.
Is That a Fact!One joule is approximately the amount of energy required to lift an apple 1 m. In sports, some activities require consid-erably more energy. The average serve of a tennis ball requires 75 J of kinetic energy, a single fastball pitch requires 120 J, and a forward pass in football requires 150 J.
Potential EnergyNot all energy has to do with motion. Potential energyPotential energy is theenergy an object has because of its position. For example, thestretched bow shown in Figure 3 has potential energy. The bowhas energy because work has been done to change its shape.The energy of that work is turned into potential energy.
Gravitational Potential EnergyWhen you lift an object, you do work on it. You use a forcethat is against the force of gravity. When you do this, youtransfer energy to the object and give the object gravitationalpotential energy. Books on a shelf have gravitational potentialenergy. So does your backpack after you lift it on to your back.The amount of gravitational potential energy that an objecthas depends on its weight and its height.
Calculating Gravitational Potential EnergyYou can find gravitational potential energy by using thefollowing equation:
Because weight is expressed in newtons and height in meters,gravitational potential energy is expressed in newton-meters(N•m), or joules (J).
Recall that work � force � distance. Weight is the amountof force that you must use on an object to lift it, and heightis a distance. So, gravitational potential energy is equal tothe amount of work done on the object to lift it to a certainheight. Or, you can think of gravitational potential energy asbeing equal to the work that would be done by the object ifit were dropped from that height.
gravitational potential energy � weight � height
Figure 3 The stored potentialenergy of the bow and stringallows them to do work onthe arrow when the string isreleased.
Gravitational Potential Energy What is thegravitational potential energy of a book witha weight of 13 N at a height of 1.5 m off theground?
Step 1: Write the equation for gravitationalpotential energy (GPE).
GPE � weight � height
Step 2: Replace the weight and height with themeasurements given in the problem,and solve.
GPE � 13 N � 1.5 m
GPE � 19.5 N•m � 19.5 J
Now It’s Your Turn1. What is the gravitational potential
energy of a cat that weighs 40 N stand-ing on a table that is 0.8 m above theground?
2. What is the gravitational potentialenergy of a diver who weighs 500 Nstanding on a platform that is 10 m offthe ground?
3. What is the gravitational potentialenergy of a diver who weighs 600 Nstanding on a platform that is 8 m offthe ground?
Potential and Kinetic Energy ina Pendulum Use a pendulum toshow the difference betweenpotential energy and kineticenergy. As you pull the pendu-lum to the side, explain that youare giving it potential energy.Write the term potential energyon the board. Draw a picture ofthe pendulum’s position next tothe term. Allow the pendulumto swing down, and write theterm kinetic energy on the board.Discuss with students the differ-ence between kinetic energy andpotential energy. l Visual
Answers to Math Focus
1. GPE � 40 N � 0.8 m � 32 J2. GPE � 500 N � 10 m � 5,000 J3. GPE � 600 N � 8 m � 4,800 J
CulturalAwarenessCulturalAwareness g
Origins of Bungee Jumping Bungeejumping began as a ritual called landdiving that was practiced by the peopleof Pentecost Island in the Pacific archi-pelago of Vanuatu. Every year, a towerthat is about 25 m tall is built. Menwith vines attached to their ankles divefrom platforms on the tower. Membersof the Dangerous Sport Club at OxfordUniversity, England, held the firstbungee jump off a bridge in 1979.
242 Chapter 9 • Energy and Energy Resources
Height Above What?When you want to find out an object’s gravitational potential energy, the “ground” that you measure the object’s height from depends on where it is. For example, what if you want to measure the gravitational potential energy of an egg sitting on the kitchen counter? In this case, you would measure the egg’s height from the floor. But if you were holding the egg over a balcony several stories from the ground, you would measure the egg’s height from the ground! You can see that gravitational potential energy depends on your point of view. So, the height you use in calculating gravitational poten-tial energy is a measure of how far an object has to fall.
Mechanical EnergyHow would you describe the energy of the juggler’s pins in Figure 4? To describe their total energy, you would state their mechanical energy. Mechanical energy is the total energy of motion and position of an object. Both potential energy and kinetic energy are kinds of mechanical energy. Mechanical energy can be all potential energy, all kinetic energy, or some of each. You can use the following equation to find mechanical energy:
✓Reading Check What two kinds of energy can make up the
mechanical energy of an object?
Mechanical Energy in a Juggler’s PinThe mechanical energy of an object remains the same unless it transfers some of its energy to another object. But even if the mechanical energy of an object stays the same, the potential energy or kinetic energy it has can increase or decrease.
Look at Figure 4. While the juggler is moving the pin with his hand, he is doing work on the pin to give it kinetic energy. But as soon as the pin leaves his hand, the pin’s kinetic energy starts changing into potential energy. How can you tell that the kinetic energy is decreasing? The pin slows down as it moves upwards. Eventually, all of the pin’s kinetic energy turns into potential energy, and it stops moving upward.
As the pin starts to fall back down again, its potential energy starts changing back into kinetic energy. More and more of its potential energy turns into kinetic energy. You can tell because the pin speeds up as it falls towards the ground.
potential energy the energy that an object has because of the position, shape, or condition of the object
mechanical energy � potential energy � kinetic energy
Figure 4 As a pin is juggled, its mechanical energy is the sum of its potential energy and its kinetic energy at any point.
mechanical energy the amount of work an object can do because of the object’s kinetic and potential energies
Gravity and Potential EnergyTell students that objects on the moon weigh one-sixth of what they weigh on Earth. Ask stu-dents to suppose that an ele-phant that has a mass of 4,000 kg goes to the moon to participate in the Elephant Olympics. Then, ask students what the elephant’s gravitational potential energy would be if the elephant stood on the 3 m div-ing board and waited for its turn to dive. (Hint: 1 kg � approximate 10 N on Earth, so 4,000 kg � 10 �40,000 N. The elephant on the diving board on the moon would have gravitational potential energy of approximately 20,000 J � 40,000 N � 1/6 � 3 m). l Logical
Answer to Reading Check
kinetic energy and potential energy
StrategiesStrategiesINCLUSIONINCLUSION
• Developmentally Delayed• Hearing Impaired• Learning DisabledFor some students, an entire chapter of information is a lot to handle, and sum mar-izing the key ideas from a chapter makes the informa-tion more manageable. Divide the class into teams. Ask each team to create a poster show-ing some examples of the following types of energy: thermal, chemical, electrical, sound, light, and nuclear. l Interpersonal ccMISCONCEPTION
ALERT
Non-conservation of Mechanical EnergyAt this point in the chapter, the discus-sion of mechanical energy does not yet take friction into account. As the pins are juggled, some of their mechanical energy is converted into thermal energy because of friction and air resistance. The role of friction in the conservation of mechanical energy is discussed in subsequent sections of this chapter.
Potential Energy in a Music Box Before a music box will play music, it must be wound up. When you wind a music box, you do work on the spring inside. The energy required to do this work gets stored as potential energy. The music box then has the ability to do the work of playing music. An example of a simi-lar device is a windup watch.
Section 1 • What Is Energy? 243
ENG-P01-007c
Other Forms of EnergyEnergy can come in a number of forms besides mechanicalenergy. These forms of energy include thermal, chemical,electrical, sound, light, and nuclear energy. As you read thenext few pages, you will learn what these different forms ofenergy have to do with kinetic and potential energy.
Thermal EnergyAll matter is made of particles that are always in randommotion. Because the particles are in motion, they have kineticenergy. Thermal energy is all of the kinetic energy due torandom motion of the particles that make up an object.
As you can see in Figure 5, particles move faster at highertemperatures than at lower temperatures. The faster theparticles move, the greater their kinetic energy and the greaterthe object’s thermal energy. Thermal energy also depends onthe number of particles. Water in the form of steam has a highertemperature than water in a lake does. But the lake has morethermal energy because the lake has more water particles.
Chemical EnergyWhere does the energy in food come from? Food is made ofchemical compounds. When compounds such as sugar form,work is done to join the different atoms together. Chemicalenergy is the energy of a compound that changes as its atomsare rearranged. Chemical energy is a form of potential energybecause it depends on the position and arrangement of theatoms in a compound.
The particles in an ice cubevibrate in fixed positions and donot have a lot of kinetic energy.
The particles of water in a lakecan move more freely and havemore kinetic energy than waterparticles in ice do.
The particles of water in steammove rapidly, so they have moreenergy than the particles in liquidwater do.
Thermal Energy in WaterFigure 5
For another activity relatedto this chapter, go togo.hrw.com and type in thekeyword HP5ENGW.
vv--------------------------------------a
El Niño The thermal energy ofEarth’s oceans has a profoundeffect on climate and weather.An example of this effect is thephenomenon known as El Niñoand its counterpart, La Niña.Have students research El Niñoand La Niña and write a reportor create a poster that describeshow thermal energy is responsi-ble for them. l Logical
Using the Figure -----g
Thermal Energy Use Figure 5to help students understand thatthe thermal energy of a sub-stance is related to the sub-stance’s temperature as well asto its state. Point out the differ-ence in the appearance of theparticles of ocean water and theparticles of steam. Explain thatat 100°C, equal masses of liquidwater and steam have differentamounts of thermal energy. Thereason is that work must bedone to force particles of liquidwater apart when water changesto steam. The energy used to dothis work is stored by the parti-cles of steam as potential energy.As a result, the steam has morethermal energy than the liquidwater does. l Visual
CHAPTER RESOURCESTechnology
Transparencies• P33 Thermal Energy in Water
Heat Versus Thermal Energy Studentsmay confuse heat with thermal energy.Energy is transferred from higher-temperature objects to lower-temperature objects. Heat is this energyas it is being transferred. After the energyis transferred, it is thermal energy.
MISCONCEPTIONALERT
244 Chapter 9 • Energy and Energy Resources
Electrical EnergyThe electrical outlets in your home allow you to useelectrical energy. Electrical energy is the energy of movingelectrons. Electrons are the negatively charged particlesof atoms.
Suppose you plug an electrical device, such as theamplifier shown in Figure 6, into an outlet and turn iton. The electrons in the wires will transfer energy todifferent parts inside the amplifier. The electrical energyof moving electrons is used to do work that makes thesound that you hear from the amplifier.
The electrical energy used in your home comes frompower plants. Huge generators turn magnets inside loopsof wire. The changing position of a magnet makeselectrical energy run through the wire. This electricalenergy can be thought of as potential energy that is usedwhen you plug in an electrical appliance and use it.
Sound EnergyFigure 7 shows how a vibrating object trans-mits energy through the air around it. Soundenergy is caused by an object’s vibrations.When you stretch a guitar string, the stringstores potential energy. When you let thestring go, this potential energy is turned intokinetic energy, which makes the string vibrate.The string also transmits some of this kineticenergy to the air around it. The air particlesalso vibrate, and transmit this energy to yourear. When the sound energy reaches your ear,you hear the sound of the guitar.
✓Reading Check What does sound energy
consist of?
Figure 6 Themovement ofelectrons producesthe electricalenergy that anamplifier and amicrophone use toproduce sound.
Hear That Energy!1. Make a simple drum by covering the open
end of an empty coffee can with wax paper.Secure the wax paper with a rubber band.
2. Using the eraser end of a pencil, tap lightlyon the wax paper. Describe how the paperresponds. What do you hear?
3. Repeat step 2, but tap the paper a bit harder.Compare your results with those of step 2.
4. Cover half of the wax paper with one hand.Now, tap the paper. What happened? Howcan you describe sound energy as a form ofmechanical energy?
Figure 7 As the guitar strings vibrate,they cause particles in the air to vibrate.These vibrations transmit sound energy.
Electrical Energy in the HomeToday, we take electrical energyfor granted. It is always there atthe flick of a switch. However, aslate as 1930, only 1 out of 10rural homes in the United Stateshad electric service. Runninglines many miles out to homesin the countryside was costly,and many power companies didnot spend the money to do so.In 1935 and 1936, the RuralElectrification Administration(REA) was established to provideelectrical energy to rural homesand farms. The REA made loansto nonprofit cooperatives tobuild electric systems in ruralareas. Because of the REA, morethan 99% of rural homes andfarms in the United States nowhave electric service.
M A T E R I A L SFOR EACH STUDENT
• coffee can, empty• pencil with an eraser• rubber band• wax paper
Answers
2. Sample answer: a soundsomething like a drum
3. Sample answer: The soundwas louder when I tappedharder. The paper has alarger vibration when it is hitharder. This larger vibrationcauses the air particles nearthe paper to vibrate more.More energy is transmittedby the air particles, so thesound is louder.
4. Sample answer: The paperwas not able to vibrate asmuch when it was held still,so the sound was more muf-fled. Sound energy is a formof mechanical energybecause vibration involves achange of position andchanges in back-and-forthmotion.
Answer to Reading Check
Sound energy consists of vibrations carriedthrough the air.
SUPPORT FOR
English Language LearnersEnergy Types To check comprehen-sion of the types of energy learned inthis section, ask groups of 4 studentsto make a poster. The posters shouldinclude drawings or cutout photos frommagazines illustrating each differenttype of energy. Examples should begrouped together and labeled by energytype. Check the posters for accuracy andspelling, and have students make correc-tions if necessary. Display the completedposters around the class.l Verbal/Visual/Interpersonal Section 1 • What Is Energy? 245
Light EnergyLight allows you to see, but did you know that not all light can be seen? Figure 8 shows a type of light that we use but can’t see. Light energy is produced by the vibrations of electrically charged particles. Like sound vibrations, light vibrations cause energy to be transmitted. But the vibrations that transmit light energy don’t need to be carried through matter. In fact, light energy can move through a vacuum (an area where there is no matter).
Nuclear EnergyThere is a form of energy that comes from a tiny amount of matter. It is used to generate electrical energy, and it gives the sun its energy. It is nuclear (NOO klee uhr) energy, the energy that comes from changes in the nucleus (NOO klee uhs) of an atom.
Atoms store a lot of potential energy because of the positions of the particles in the nucleus of the atoms. When two or more small nuclei (NOO klee ie) join together, or when the nucleus of a large atom splits apart, energy is given off.
The energy given off by the sun comes from nuclear energy. In the sun, shown in Figure 9, hydrogen nuclei join together to make a larger helium nucleus. This reaction, known as fusion,gives off a huge amount of energy. The sun’s light and heat come from these reactions.
When a nucleus of a heavy element such as uranium is split apart, the potential energy in the nucleus is given off. This kind of nuclear energy is called fission. Fission is used to generate electrical energy at nuclear power plants.
✓Reading Check Where does nuclear energy come from?
Figure 9 Without the nuclear energy from the sun, life on Earth would not be possible.
Figure 8 The energy used to cook food in a microwave is a form of light energy.
246 Chapter 9 • Energy and Energy Resources
Reteaching -------------------------------------bDifferent Kinds of EnergyOn the board, list each type of energy mentioned in this sec-tion (show mechanical energy as comprising both kinetic and potential energy). Ask students to brainstorm examples of each kind of energy. l Logical
1. Compare energy and work. What does one have to do with the other? (Energy is the ability to do work. Work cannot occur without energy.)
2. What is the difference between kinetic and potential energy? Can you describe an object that has both? (Kineticenergy is the energy of motion. Potential energy is the energy that an object has because of the object’s position or shape. A child’s swing has both kinetic and potential energy.)
Alternative Assessment ---------------------------g
Different Forms of Energy Ask students to list and describe in their science journal examples of at least three forms of energy. One source should relate to their own body. l Intrapersonal
Answer to Reading Check
Nuclear energy comes from changes in the nucleus of an atom.
Nuclear Fusion Hydrogen nuclei can join together to form a helium nucleus only at temperatures close to 100,000,000°C! For this reason, duplicat-ing this reaction on Earth is not practical.
For a variety of links related to this chapter, go to www.scilinks.org
SummarySummary
Review
• Energy is the ability to do work, and work equals the transfer of energy. Energy and work are expressed in units of joules (J).
• Kinetic energy is energy of motion and depends on speed and mass.
• Potential energy is energy of position. Gravitational potential energy depends on weight and height.
• Mechanical energy is the sum of kinetic energy and potential energy.
• Thermal energy and sound energy can be considered forms of kinetic energy.
• Chemical energy, electrical energy, and nuclear energy can be considered forms of potential energy.
Using Key Terms
1. In your own words, write a definition for the term energy.
2. Use the following terms in the same sentence: kinetic energy, potential energy,and mechanical energy.
Understanding Key Ideas
3. What determines an object’s thermal energy?
a. the motion of its particlesb. its sizec. its potential energyd. its mechanical energy
4. How are energy and work related?
5. What two factors determine gravitational potential energy?
6. Describe why chemical energy is a form of potential energy.
Critical Thinking
7. Identifying Relationships When you hit a nail into a board by using a hammer, the head of the nail gets warm. In terms of kinetic and thermal energy, describe why you think the nail head gets warm.
8. Applying Concepts Explain why a high-speed collision may cause more damage to vehicles than a low-speed collision does.
Interpreting Graphics
9. Which part of mechanical energy does the girl in the picture below have the most of?
Topic: What Is Energy? ; Forms of EnergySciLinks code: HSM1660; HSM0612
Section 1 • What Is Energy? 247
Answers to Section Review
1. Sample answer: Energy is the ability to do work.
2. Sample answer: Mechanical energy can consist of kinetic energy, potential energy, or both.
3. a4. Energy is the ability to do work.5. weight and height6. It depends on the position of
atoms in a molecule.7. Kinetic energy is used to nail the
hammer into the board, and that energy becomes thermal energy.
8. A vehicle moving at high speed has a lot more kinetic energy than a vehicle moving at low speed does, so the high-speed vehicle is able to cause more damage in a collision.
9. potential energy
CHAPTER RESOURCES
Chapter Resource File
• Section Quiz g• Section Review g• Vocabulary and Section Summary g• SciLinks Activity g• Datasheet for Quick Lab
CRF
READING STRATEGY
Energy ConversionsImagine you’re finishing a clay mug in art class. You turn around, and your elbow knocks the mug off the table. Luckily, you catch the mug before it hits the ground.
The mug has gravitational potential energy while it is on thetable. As the mug falls, its potential energy changes into kineticenergy. This change is an example of an energy conversion. Anenergy conversionenergy conversion is a change from one form of energy toanother. Any form of energy can change into any other form ofenergy. Often, one form of energy changes into more than oneother form.
Kinetic Energy and Potential EnergyLook at Figure 1. At the instant this picture was taken,the skateboarder on the left side of the picture was hardlymoving. How did he get up so high in the air? As you mightguess, he was moving at a high speed on his way up thehalf-pipe. So, he had a lot of kinetic energy. What happenedto that energy? His kinetic energy changed into potentialenergy. Imagine that the picture below is a freeze-frame of avideo. What happens once the video starts running again? Theskateboarder’s potential energy will become kinetic energy onceagain as he speeds down the side of the half-pipe.
2
energy conversionenergy conversion a change from one form of energy to another
Potential Energy and Kinetic EnergyFigure 1
When the skateboarder reaches the top of the half-pipe, his potential energy is at a maximum.
As he speeds down through the bot-tom of the half-pipe, the skateboarder’s kinetic energy is at a maximum.
What You Will Learn
Describe an energy conversion.Give examples of energy conversionsfor the different forms of energy.Explain how energy conversionsmake energy useful.Explain the role of machines inenergy conversions.
Vocabularyenergy conversion
Brainstorming The key idea ofthis section is energy conversion.Brainstorm words and phrasesrelated to energy conversion.
OverviewThis lesson discusses energy con-versions. Students will be givenexamples of ways that energyis converted from one form toanother. This section also explainsthe role of machines in energyconversions.
BellringerDisplay a plant, a Bunsen burneror small propane camping stove,and a pendulum. Ask studentswhat they think these objectshave in common. (All are capableof converting energy from one formto another.)
Discussion ----------------------------------gKinetic and Potential EnergyHave a windup alarm clock setup for students to see. Display alabel next to the clock that reads“Potential energy.” The clockshould be wound and set to gooff when students are seated andattentive. When the clock alarmsounds, turn the label aroundso that it reads “Kinetic energy.”Ask students to try to definekinetic energy and potentialenergy based on the demonstra-tion. You may need to describehow the alarm clock works. Leada discussion that addressesenergy conversions. l Logical
Elastic Potential EnergyA rubber band can be used to show another example of an energy conversion. Did you know that energy can be stored in a rubber band? Look at Figure 2. The wound-up rubber band in the toy airplane has a kind of potential energy called elastic potential energy. When the rubber band is let go, the stored energy becomes kinetic energy, spins the propeller, and makes the airplane fly.
You can change the shape of a rubber band by stretch-ing it. Stretching the rubber band takes a little effort. The energy you put into stretching it becomes elastic potential energy. Like the skateboarder at the top of the half-pipe, the stretched rubber band stores potential energy. When you let the rubber band go, it goes back to its original shape. It releases its stored-up potential energy as it does so, as you know if you have ever snapped a rubber band against your skin!
✓Reading Check How is elastic potential energy stored
and released? (See the Appendix for answers to Reading Checks.)
Conversions Involving Chemical Energy You may have heard someone say, “Breakfast is the most important meal of the day.” Why is eating breakfast so important? As shown in Figure 3, chemical energy comes from the food you eat. Your body uses chemical energy to function. Eating breakfast gives your body the energy needed to help you start the day.
Figure 3 Chemical energy of food is converted into kinetic energy when you are active. It is converted into thermal energy to maintain body temperature.
Figure 2 The wound-up rubber band in this model airplane has potential energy because its shape has been changed.
Using the Figure -----gConversions of Potential and Kinetic Energy Use Figure 1to help students understand the conversion of potential energy to kinetic energy. Then, display a pendulum, and use it to illus-trate the energy conversions. Discuss how the pendulum dis-plays potential energy (at the top of the swing) and kinetic energy (as it moves through the swing). When the pendulum is at the top of its swing, kinetic energy is 0. When the pendu-lum is at the bottom of its swing, potential energy is 0. Make sure that students under-stand why the value for each kind of energy at the respective position is 0. l Visual
Answer to Reading Check
Elastic potential energy can be stored by stretching a rubber band. Elastic potential energy is released when the rubber band goes back to its original shape.
Is That a Fact!One appliance that uses a great deal of electrical energy (4,200 to 4,800 kWh per year) is the water heater. At the other extreme, an electric toothbrush uses only about 5 kWh per year.
If sound waves could be converted into electrical energy, 100 quadrillion (1015)mosquitoes buzzing could power a read-ing lamp.
Section 2 • Energy Conversions 249
Sugar in food
Light Energy Chlorophyll ingreen leaves
Carbondioxidein the air
Water in the soil
Photosynthesis
sugar � oxygencarbon dioxide� water
light energy
chlorophyll
Energy Conversions in PlantsDid you know that the chemical energy in the food you eatcomes from the sun’s energy? When you eat fruits, vegetables,or grains, you are taking in chemical energy. This energy comesfrom a chemical change that was made possible by the sun’senergy. When you eat meat from animals that ate plants, youare also taking in energy that first came from the sun.
As shown in Figure 4, photosynthesis (FOHT oh SIN thuhsis) uses light energy to make new substances that havechemical energy. In this way, light energy is changed intochemical energy. The chemical energy from a tree can bechanged into thermal energy when you burn the tree’s wood.So, if you follow the conversion of energy back far enough,the energy from a wood fire actually comes from the sun!
✓Reading Check Where does the energy that plants use to grow
come from?
The Process ContinuesLet’s trace where the energy goes. Plants change light energyinto chemical energy. The chemical energy in the food youeat is changed into another kind of chemical energy that yourbody can use. Your body then uses that energy to give youthe kinetic energy that you use in everything you do. It’s anendless process—energy is always going somewhere!
From Light Energy to Chemical EnergyFigure 4
Energy fromPlants All living
things need energy. Plantsplay a major role in provid-ing sources of energy that ourbodies use, from the oxygenwe breathe to the food weeat. Research the differentways that plants help providethe energy requirements ofall living things, and write aone-page report in yourscience journal describingwhat you learn.
WRITINGSKILL
MISCONCEPTIONALERT
Energy from Food Studentsmay assume that they getenergy from the sun onlywhen they eat plants or plantproducts. However, when aperson eats meat, that personis still getting energy fromthe sun. For example, a cowgets energy from the sun byeating plants. The cow storessome of this energy in itscells. When a person eatsbeef, that person’s body usesthe energy that was stored inthe cow’s cells. This energyoriginally came from the sun.
CONNECTIONCONNECTION vvEnvironmentalScience ----------------------------------------------------gPhotosynthesis in Rain ForestsDivide the class into two groups.Have one group research therate of growth and the rate ofphotosynthesis in tropical rainforests. Have the second groupresearch the rate of rain-forestdestruction. Ask both groups topresent their findings to theclass. Encourage a discussion ofthe usefulness of photosynthesisversus the usefulness of clearingthe land occupied by rainforests. l Logical
Answer to Reading Check
Plants get their energy from the sun.CHAPTER RESOURCES
Technology
Transparencies• P35 From Light Energy to Chemical Energy
Workbooks
Math Skills for Science• A Bicycle Trip
250 Chapter 9 • Energy and Energy Resources
Why Energy Conversions Are ImportantEnergy conversions are needed for everything we do. Heat-ing our homes, getting energy from a meal, and many otherthings use energy conversions. Machines, such as the hair dryershown in Figure 5, help harness energy and make that energywork for you. Electrical energy by itself won’t dry your hair.But you can use a hair dryer to change electrical energy intothe thermal energy that will help you dry your hair.
Conversions Involving Electrical EnergyYou use electrical energy all of the time. When you listen tothe radio, when you make toast, and when you take a picturewith a camera, you use electrical energy. Electrical energy caneasily be changed into other forms of energy. Table 1 lists somecommon energy conversions that involve electrical energy.
Electrical energyenters the hairdryer and isconverted intokinetic energy asa small electricmotor spins afan blade.
Electrical energyis also convertedinto thermalenergy in a gridof wires thatheats up.
The fan forces airacross the hot wires,and hot air blows outof the nozzle of thehair dryer. You canhear the sound energythat also comes out.
Table 1 Some Conversions of Electrical Energy
Alarm clock electrical energy light energy and sound energy
Battery chemical energy electrical energy
Light bulb electrical energy light energy and thermal energy
Blender electrical energy kinetic energy and sound energy
Energy Conversions in a Hair DryerFigure 5
1
2
3
Using the Figure -----gConcept Mapping Have stu-dents refer to Figure 5 andTable 1 to create a concept mapof ways that electrical energy isconverted. The map shouldbegin with the nature of thework done on each object andend with the type(s) of energyproduced. l Visual
CulturalAwarenessCulturalAwareness g
Bicycles for DailyTransportation There aremore than 33 million cyclistsin the United States. Mostpeople in the United Statesride bicycles for competition,recreation, or exercise, butpeople in other parts of theworld use bicycles for dailytransportation. For example,people in China often use abicycle when they need totravel short distances, such asfrom home to work. Howwould U.S. traffic problemsbe different if most people inthe United States rode bicy-cles to work? l Logical
A Nuclear Car? The design for anuclear-powered automobile was pro-posed by Ford automotive designers inthe 1950s. The name of the car was tobe the Ford Nucleon, and the car was tobe propelled by a small atomic reactorlocated in the rear of the car. For severalreasons, the car was never built.
Is That a Fact!Only about 20% of the energy releasedby burning gasoline in a car engine isconverted to kinetic energy to movethe car forward. Most of the rest isconverted to thermal energy, whichis wasted.
SUPPORT FOR
English LanguageLearnersEnergy Conversions in theHome Show pictures of somecommon machines studentsmight find at home one at atime. Have students note thename of the machine andthe kind of energy conver-sion that may occur in it.Call on volunteers to sharetheir responses with the class.l Visual/Verbal
Section 2 • Energy Conversions 251
Energy and MachinesYou’ve been learning about energy, its different forms, and the ways that it can change between forms. Another way to learn about energy is to look at how machines use energy. A machine can make work easier by changing the size or direction (or both) of the force needed to do the work.
Suppose you want to crack open a walnut. Using a nutcracker, such as the one shown in Figure 6, would be much easier (and less painful) than using your fingers. You transfer energy to the nutcracker, and it transfers energy to the nut. The nutcracker allows you to use less force over a greater distance to do the same amount of work as if you had used your bare hands. Another example of how energy is used by a machine is shown in Figure 7. Some machines change the energy put into them into other forms of energy.
✓Reading Check What are two things that machines can
do to force that is put into them?
Figure 6 Some of the energy you transfer to a nutcracker is converted into sound energy as the nutcracker transfers energy to the nut.
Chemical energy in your body is converted into kinetic energy when your muscle fibers contract and relax.
1
Your legs transfer this kinetic energy to the pedals by pushing them around in a circle.
2
The pedals transfer this kinetic energy to the gear wheel, which transfers kinetic energy to the chain.
3The chain moves and transfers energy to the back wheel, which gets you moving!
4
Energy Conversions in a BicycleFigure 7
For your bike to start and keep moving, energy must be transferred and converted.
252 Chapter 9 • Energy and Energy Resources
Reteaching -------------------------------------bEnergy Conversions in Appliances Bring a few small appliances to class. Plug them in, demonstrate their operation (if feasible), and challenge students to identify the energy conversions taking place in each, as Table 1 does. l Visual
1. Give an example of an energy conversion that produces a useful result. (Answers may vary, but students might mention the conversion of chemical energy in their food into the kinetic energy of their movements.)
2. Demonstrate the conversion of potential energy to kinetic energy by using a pendulum model. (As the pendulum is lifted upward, it gains potential energy. When the pendulum is released and swings downward, that potential energy is converted to kinetic energy.)
Alternative Assessment ---------------------------g
Daily Energy Use Ask students to categorize their daily activ-ities according to the forms of energy the activities use. Cat -egories could include electrical energy, chemical energy, and mechanical energy. Instruct students to try to list five activities for each category. l Intrapersonal
Answer to Reading Check
Machines can change the size or direction of the input force.
For a variety of links related to thischapter, go to www.scilinks.org
SummarySummary
Review
Machines as Energy ConvertersMachines help you use energy by converting it into the formthat you need. Figure 8 shows a device called a radiometer.It was invented to measure energy from the sun. Inside theglass bulb are four small vanes that absorb light energy. Thevanes are dark on one side and light on the other. The darksides absorb light energy better than the light sides do. Asgases next to the dark sides of the vanes heat up, the gasmolecules move faster, which causes the vanes to turn. Theradiometer shows how a machine can convert energy from oneform into another. It changes light energy into heat energyinto kinetic energy.
• An energy conversion isa change from one formof energy to another.Any form of energy canbe converted into anyother form of energy.
• Kinetic energy isconverted to potentialenergy when an objectis moved against gravity.
• Elastic potential energyis another example ofpotential energy.
• Your body uses thefood you eat to convertchemical energy intokinetic energy.
• Plants convert lightenergy into chemicalenergy.
• Machines can transferenergy and can convertenergy into a moreuseful form.
Using Key Terms
1. In your own words, write adefinition for the term energyconversion.
Understanding Key Ideas
2. In plants, energy istransformed from
a. kinetic to potential.b. light to chemical.c. chemical to electrical.d. chemical to light.
3. Describe a case in whichelectrical energy is convertedinto thermal energy.
4. How does your body get theenergy that it needs?
5. What is the role of machines inenergy conversions?
7. Applying Concepts A carthat brakes suddenly comesto a screeching halt. Is thesound energy produced in thisconversion a useful form ofenergy? Explain your answer.
Interpreting Graphics
Look at the diagram below, andanswer the following questions.
8. What kind of energy doesthe skier have at the top ofthe slope?
9. What happens to that energyafter the skier races down theslope of the mountain?
Topic: Energy ConversionsSciLinks code: HSM0511
Figure 8 Machines can changeenergy into different forms. Thisradiometer converts light energyinto kinetic energy.
Answers to Section Review
1. Sample answer: a change fromone kind of energy to another
2. b3. Sample answer: a space heater,
whose heating coils are giventhermal energy from electricalenergy when the heater isplugged in
4. Your body gets its energy fromchemical energy found in food.
5. Machines can convert energyinto more useful forms of energy.
6. The potential energy of a basket-ball is at a maximum when theball is at its greatest height. Thepotential energy becomes con-verted to kinetic energy as theball falls to the ground, andkinetic energy is at a maximumas the ball reaches the ground.When the ball bounces back upagain, its kinetic energy is onceagain converted into potentialenergy, and so on.
7. No, the sound produced byscreeching brakes is not a usefulform of energy, because it doesnot contribute to stopping thecar.
8. potential energy9. It is converted to kinetic energy.
Transparencies • LINK TOLINK TO LIFE SCIENCELIFE SCIENCE L46 Photosynthesis
• P36 Energy Conversions in a Bicycle
CRF
Section 2 • Energy Conversions 253
READING STRATEGY
Conservation of EnergyMany roller coasters have a mechanism that pulls the cars up to the top of the first hill. But the cars are on their own for the rest of the ride.
As the cars go up and down the hills on the track, theirpotential energy is converted into kinetic energy and backagain. But the cars never return to the same height at whichthey started. Does energy get lost somewhere along the way?No, it is just converted into other forms of energy.
Where Does the Energy Go? To find out where a roller coaster’s original potential energygoes, you have to think about more than just the hills of theroller coaster. Friction plays a part too. FrictionFriction is a force thatopposes motion between two surfaces that are touching. Forthe roller coaster to move, energy must be used to overcomefriction. There is friction between the cars’ wheels and thetrack and between the cars and the air around them. As aresult, not all of the potential energy of the cars changes intokinetic energy as the cars go down the first hill. Likewise, asyou can see in Figure 1, not all of the kinetic energy of thecars changes back into potential energy.
Not all of the cars’ potential energy (PE) is converted into kinetic energy (KE) as the cars go down the first hill. In addition, not all of the cars’ kinetic energy is converted into potential energy as the cars go up the second hill. Some of it is changed into thermal energy because of friction.
PE is greatest at the top of the first hill.
KE at the bottom of the first hill is less than the PE at the top was.
PE at the top of the sec-ond hill is less than KEand PE from the first hill.
a
c
b
3
Energy Conversions in a Roller CoasterFigure 1
What You Will Learn
Explain how energy is conserved within a closed system.Explain the law of conservation of energy.Give examples of how thermal energy is always a result of energy conversion.Explain why perpetual motion is impossible.
Vocabularyfrictionlaw of conservation of energy
Paired Summarizing Read this section silently. In pairs, take turns summarizing the material. Stop to discuss ideas that seem confusing.
OverviewThis section introduces the lawof conservation of energy. Stu-dents will learn how all energyis continuously being convertedinto other forms, and they willlearn why the principle of energyconversion makes perpetualmotion impossible.
BellringerPose the following questionsto students:
• Where does the energy thatmakes a roller coaster car movecome from?
• Where does the energy go?
• What does “All of the energyput into a process still existssomewhere when the processhas ended” mean?
Demonstration --------------gWhere Does the Energy Go?Show students a high-densityrubber ball. Explain that it wasdesigned to bounce for a longtime but that it must eventuallystop. Allow the ball to beginbouncing. As it bounces, ask stu-dents to observe both the heightand the number of bounces. Askthem to theorize why the balleventually stops. Ask them whathappens to the kinetic energy ofthe ball’s movement. l Logical
3
MISCONCEPTIONALERT
Energy Lost as Friction Studentsmay assume that all processes involv-ing work and energy are 100% effi-cient. Remind students that all motionand all processes involving work areopposed by friction. Friction convertskinetic energy into thermal energy. Letstudents rub their palms together for30 s. They will feel the thermal energyproduced by friction.
Transparencies• Bellringer• P37 Energy Conversions in a Roller Coaster
254 Chapter 9 • Energy and Energy Resources
Energy Is Conserved Within a Closed SystemA closed system is a group of objects that transfer energy onlyto each other. For example, a closed system that involves aroller coaster consists of the track, the cars, and the air aroundthem. On a roller coaster, some mechanical energy (the sumof kinetic and potential energy) is always converted intothermal energy because of friction. Sound energy also comes fromthe energy conversions in a roller coaster. If you add togetherthe cars’ kinetic energy at the bottom of the first hill, thethermal energy due to overcoming friction, and the soundenergy made, you end up with the same total amount ofenergy as the original amount of potential energy. In otherwords, energy is conserved and not lost.
Law of Conservation of EnergyEnergy is conserved in all cases. Because no exception to thisrule has been found, this rule is described as a law. Accordingto the law of conservation of energy, energy cannot be createdor destroyed. The total amount of energy in a closed system isalways the same. As Figure 2 shows, energy can change fromone form to another. But all of the different forms of energyin a system always add up to the same total amount of energy.It does not matter how many energy conversions take place.
✓Reading Check Why is the conservation of energy considered ascientific law? (See the Appendix for answers to Reading Checks.)
friction a force that opposesmotion between two surfacesthat are in contact
Some energy is con-verted into thermalenergy, which makesthe bulb feel warm.
Some electricalenergy is convertedinto light energy.
As electrical energy iscarried through the wire,some of it is convertedinto thermal energy.
law of conservation of energythe law that states that energycannot be created or destroyedbut can be changed from oneform to another
Chemical Energy to ThermalEnergy Divide the class intothree groups, and go outside asa class. This activity will explorehow the body converts chemicalenergy to thermal energy. Onegroup should simply stand orsit for 5 min. Meanwhile, thesecond group should walk at acomfortable pace, and the thirdgroup should engage in a run-ning activity. After 5 min, havestudents discuss the amountof thermal energy producedby their bodies. Ask students,“Which group produced themost thermal energy? Whichproduced the least? Why?”l Kinesthetic
Answer to Reading Check
Conservation of energy is con-sidered a scientific law becauseno exception to it has ever beenobserved.
Is That a Fact!At extremely low temperatures, somematerials become superconductors,materials that have no resistance to theflow of electrical energy. These materialsare used to create giant electromagnetsthat generate strong magnetic fieldswith very little thermal-energy loss.
SUPPORT FOR
English Language LearnersLaw of Conservation of EnergyAfter students have read the rollercoaster and light bulb charts, have stu-dents copy them in their journals. Then,reinforce the concept of conservation ofenergy by having them paraphrase theinformation. Check their work foraccuracy. Ask if students can see anysimilarities between energy on the rollercoaster and energy in the light bulb.(Both energy conversions result in somethermal energy.)l Visual/Verbal
Section 3 • Conservation of Energy 255
No Conversion Without Thermal EnergyAny time one form of energy is converted into another form,some of the original energy always gets converted into thermalenergy. The thermal energy due to friction that results fromenergy conversions is not useful energy. That is, this thermalenergy is not used to do work. Think about a car. You putgas into a car. But not all of the gasoline’s chemical energymakes the car move. Some wasted thermal energy will alwaysresult from the energy conversions. Much of this energy leavesthrough the radiator and the exhaust pipe.
Perpetual Motion? No Way!People have sometimes tried to make a machine that wouldrun forever without any additional energy. This perpetual (puhrPECH oo uhl) motion machine would put out exactly as muchenergy as it takes in. But that’s impossible, because some wastethermal energy always results from energy conversions. Theonly way a machine can keep moving is to have a constantsupply of energy. For example, the “drinking bird” shown inFigure 3 uses thermal energy from the air to evaporate the waterfrom its head. So, it is not a perpetual motion machine.
✓✓Reading Check Why is “perpetual motion” impossible?
Energy ConversionsWith an adult, find three examples of energy conver-sions that take place in your home. In your science jour-nal, write down the kinds of energy that go into each conversion and the kinds of energy that result. For each type of energy that is output, indicate whether the energy is useful.
After the bird “drinks,” fluid returns to the tail, the bird flips upright, and the cycle repeats.
When the bird “drinks,” the felt covering its head gets wet.
1
When the bird is upright, water evaporates from the felt, which decreases the temperature and pressure in the head. Fluid is drawn up from the tail, where pressure is higher, and the bird tips downward.
2
3
The “Drinking Bird”Figure 3
Reteaching -------------------------------------bConservation of Roller-CoasterEnergy Revisit Figure 1 byshowing students the transpar-ency of that figure. Ask stu -dents why each successive hill issmaller than the last, and makesure that they know where theenergy went. l Visual
1. Think of an example otherthan the ones given in thissection that illustrates thelaw of conservation of energy.(Answers may vary but shouldreflect an understanding ofenergy conservation.)
2. What condition would haveto exist for perpetual motionto be possible? (no productionof waste thermal energy; nofriction)
Energy Conservation DiagramHave students draw a diagramof a system in which energyconservation is demonstrated.The diagram should includelabels that indicate the kindsof energy involved. l Visual
Answer to Reading Check
Perpetual motion is impossible because energyconversions always result in the production ofwaste thermal energy.
256 Chapter 9 • Energy and Energy Resources
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Developed and maintained by theNational Science Teachers Association
SummarySummary
Review
Making Conversions EfficientYou may have heard that a car is energy efficient if it gets good gas mileage, and that your home may be energy efficient if it is well insulated. In terms of energy conversions, energy efficiency (e FISH uhn see) is a comparison of the amount of energy before a conversion with the amount of useful energy after a conversion. A car with high energy efficiency can go farther than other cars with the same amount of gas.
Energy conversions that are more efficient end up wasting less energy. Look at Figure 4. Newer cars tend to be more energy efficient than older cars. One reason is the smooth, aerodynamic (ER oh die NAM ik) shape of newer cars. The smooth shape reduces friction between the car and the surrounding air. Because these cars move through air more easily, they use less energy to over-come friction. So, they are more efficient. Improving the efficiency of machines, such as cars, is important because greater efficiency results in less waste. If less energy is wasted, less energy is needed to operate a machine.
• Because of friction, some energy is always converted into thermal energy during an energy conversion.
• Energy is conserved within a closed system. According to the law of conservation of energy, energy cannot be cre-ated or destroyed.
• Perpetual motion is impossible because some of the energy put into a machine is converted into thermal energy because offriction.
Using Key Terms
1. Use the following terms in the same sentence: friction and thelaw of conservation of energy.
Understanding Key Ideas
2. Perpetual motion is impossible because
a. things tend to slow down.b. energy is lost.c. machines are very inefficient.d. machines have friction.
3. Describe the energy conver-sions that take place on a roller coaster, and explain how energy is conserved.
Math Skills
4. A bike is pedaled with 80 J of energy and then coasts. It does 60 J of work in moving forward until it stops. How much of the energy that was put into the bike became thermal energy?
Critical Thinking
5. Evaluating Conclusions Imagine that you drop a ball. It bounces a few times and then it stops. Your friend says that the energy that the ball had is gone. Where did the energy go? Evaluate your friend’s statement based on energy conservation.
6. Evaluating Assumptions If someone says that a car has high energy output, can you conclude that the car is efficient? Explain.
Topic: Law of Conservation of EnergySciLinks code: HSM0856
Figure 4 The shape of newer cars reduces friction between the body of the car and the air.
More aerodynamic car
Less aerodynamic car
Answers to Section Review
1. Sample answer: According to the law of conservation of energy, energy is not lost, although kinetic energy can be converted into thermal energy by friction.
2. d3. Sample answer: At the top of a
“hill,” a roller-coaster car has maximum potential energy. As the car rolls down the hill, its potential energy is turned into kinetic energy and thermal energy due to friction. Because the car “loses” energy because of friction, the next hill that the car climbs must be lower than the first one, and so on.
4. 80 J � 60 J � 20 J5. The energy that the ball had ini-
tially is not “gone” but was con-verted into thermal energy and sound energy.
6. No, efficiency depends on the ratio of energy input to energy output, and you do not know the energy input. If the energy input is much higher than the energy output, the car is not efficient.
CHAPTER RESOURCES
Chapter Resource File
• Section Quiz g• Section Review g• Vocabulary and Section Summary g
CRF
Section 3 • Conservation of Energy 257
READING STRATEGY
Energy ResourcesEnergy is used to light and warm our homes. It is used to make food, clothing, and other things. It is also used to transport people and products from place to place. Where does all of this energy come from?
An energy resource is a natural resource that can be convertedinto other forms of energy in order to do useful work. Inthis section, you will learn about several energy resources,including the one that most other energy resources comefrom—the sun.
Nonrenewable ResourcesSome energy resources, called nonrenewable resources,nonrenewable resources, cannot bereplaced or are replaced much more slowly than they are used.Fossil fuels are the most important nonrenewable resources.
Oil and natural gas, shown in Figure 1, as well as coal, arethe most common fossil fuels. Fossil fuelsFossil fuels are energy resourcesthat formed from the buried remains of plants and animalsthat lived millions of years ago. These plants stored energyfrom the sun by photosynthesis. Animals used and stored thisenergy by eating the plants. So, fossil fuels are concentratedforms of the sun’s energy. Now, millions of years later, energyfrom the sun is released when these fossil fuels are burned.
✓✓Reading Check Why are fossil fuels considered nonrenewable resources? (See the Appendix for answers to Reading Checks.)
4
nonrenewable resourcenonrenewable resource a resource that forms at a rate that is much slower than the rate at which it is consumed
fossil fuelfossil fuel a nonrenewable energy resource formed from the remains of organisms that lived long ago
Formation of Fossil FuelsFigure 1
Crushed by sediment and heated by Earth, remains of organisms that lived millions of years ago slowly turned into oil or petroleum.
Formed in much the same way that petro-leum formed, natural gas is often found with petroleum deposits.
What You Will Learn
Name several energy resources.Explain how the sun is the sourceof most energy on Earth.Evaluate the advantages anddisadvantages of using variousenergy resources.
Reading Organizer As you readthis section, make a table comparingnonrenewable resources andrenewable resources.
OverviewStudents will learn aboutrenewable and nonrenewableenergy resources and aboutadvantages and disadvantagesof energy resources.
BellringerWrite the names of several typesof energy resources (such assunlight, coal, and wind) onthe board. Ask students to pre-dict which resources are nonre-newable and which resources arerenewable.
Sources of Energy Tell studentsto pick an activity that they doevery day. Ask them to trace theenergy involved in their activityback to its source. For example,if their activity consists of play-ing computer games, they wouldtrace the light and sound energyfrom the computer. Then, theywould trace the production ofthe electrical energy used by thecomputer back to the energy’ssource. The power plant pro-duced electrical energy from afuel such as coal or natural gas.If they can, students shouldtrace the fuel back to its source,too. l Logical
Answer to Reading Check
Fossil fuels are nonrenewable resourcesbecause they are used up more quickly thanthey are replaced.
Uses of Fossil FuelsAll fossil fuels contain stored energy from the sun, which can be converted into other kinds of energy. Figure 2 shows some different ways that fossil fuels are used in our society.
People have been getting energy from the burning of coal, a fossil fuel, for hundreds of years. Today, burning coal is still a very common way to generate electrical energy. Many products, such as gasoline, wax, and plastics, are made from petroleum, another fossil fuel. A third kind of fossil fuel, natural gas, is often used in home heating.
Finding alternative energy resources will become more impor-tant in years to come.
Most coal used in the United States is burned to pro-duce steam to run electric generators.
Gasoline, kerosene, wax, and petrochemicals come from petroleum.
Natural gas is used in heating systems, stoves, ovens, and vehicles.
Compared to other fossil fuels, natural gas has very low emission levels when burned.
Worldwide Coal DistributionThe worldwide distribution of coal reserves in billions of metric tons (1 metric ton �1,000 kg) is as follows:
• 66 in Africa
• 695 in Asia
• 404 in Europe
• 271 in North America
• 7 in South and Central America
Help students construct both a pie chart and a bar graph to display this information. Discuss the two presentations, including when each might be useful. l Logical
Writing Use of Fossil Fuels Askstudents to write a short story about how a day in
their life would be if no fossil-fuel energy (oil, gasoline, natural gas, and coal) were available. The story should include descrip tionsof when and how their daily activities would be performed, which things would be different, and which things might stay the same.l Intrapersonal PORTFOLIO
Energy Density of Fossil Fuels It takes about 454 kg of lead-acid batteries (such as the one in most cars) to store the same amount of energy that about 4 L of gasoline contains.
Is That a Fact!The pioneers who settled the American West often dug wells to find water. Occasionally, they were disappointed because they struck oil, for which they had no use!
Is That a Fact!Recycling just one aluminum can saves enough energy to run a television set for 4 h.
260 Chapter 9 • Energy and Energy Resources
Electrical Energy from Fossil FuelsOne way to generate electrical energy is to burn fossil fuels. In fact, fossil fuels are the main source of electrical energy generated in the United States. Electric generators convert the chemical energy in fossil fuels into electrical energy by the process shown in Figure 3. The chemical energy in fossil fuels is changed into the electrical energy that you use every day.
Nuclear EnergyAnother way to generate electrical energy is to use nuclear energy. Like fossil-fuel power plants, a nuclear power plant generates thermal energy that boils water to make steam. The steam then turns a turbine, which runs a generator. The spinning generator changes kinetic energy into electrical energy. However, the fuels used in nuclear power plants differ from fossil fuels. Nuclear energy is generated from radioactive elements, such as uranium, shown in Figure 4. In a process called nuclear fission (NOO klee uhr FISH uhn), the nucleus of a uranium atom is split into two smaller nuclei, which releases nuclear energy. Because the supply of these elements is limited, nuclear energy is a nonrenewable resource.
✓Reading Check Where does nuclear energy come from?
1
24
3
56
Water is pumped into a boiler.
Coal, oil, or natural gas is burned in a combustion chamber. In this way, the chemical energy of the fossil fuels is converted into thermal energy.
Thermal energy is used to boil water and turn it to steam.
Thermal energy is converted into kinetic energy as the steam pushes against the blades of a turbine and causes the central shaft to spin.
An electric generator converts kinetic energy into electrical energy. The turbine spins a large magnet within a wire coil. As the magnet spins, electric current is generated in the wire.
The electrical energy can be distributed to a community through electrical wires.
Figure 4 A single uranium fuel pellet contains the energy equivalent of about 1 metric ton of coal.
Converting Fossil Fuels into Electrical EnergyFigure 3
Using the Figure ---g
Converting Fossil Fuels into Electrical Energy Have students study Figure 3 on this page. Make sure that students under-stand each step for converting fossil fuels into electrical energy by discussing each step. Ask stu-dents to create a concept map explaining each of the steps. l Logical
StrategiesStrategiesINCLUSIONINCLUSION
• Hearing Impaired• Learning Disabled• Developmentally DelayedSimplification of information can help some students understand complicated details. To make sure that students understand the concepts of renewable energy and nonrenewable energy, put on the board a chart that has the following row head-ings: “Coal,” “Petroleum,” “Natural gas,” “Nuclear energy,” “Solar energy,” “Wind energy,” “Energy from water,” “Geothermal energy,” and “Biomass.” Make columns that have the following headings: “Renewable” and “Nonrenew-able.” As a group, discuss each resource (row headings) and place a check in either the “Renewable” or “Nonrenewable”column. l Verbal ee
Answer to Reading Check
Nuclear energy comes from radioactive elements that give off energy during nuclear fission.
Is That a Fact!The First Electrical Generator In 1882 in Manhattan, Thomas Edison built the first electrical generating station designed to provide electrical energy to homes and businesses.
Renewable ResourcesSome energy resources, called renewable resources, arenaturally replaced more quickly than they are used.Some renewable resources, such as solar energy and windenergy, are considered practically limitless.
Solar EnergySunlight can be changed into electrical energy throughsolar cells. These cells can be used in devices such ascalculators. Solar cells can also be placed on the roof ofa house to provide electrical energy. Some houses canuse solar energy by allowing sunlight into the housethrough large windows. The sun’s energy can then beused to heat the house.
Energy from WaterThe sun causes water to evaporate and fall again as rainthat flows through rivers. The potential energy of waterin a reservoir can be changed into kinetic energy as thewater flows through a dam. Figure 5 shows a hydroelectricdam. Falling water turns turbines in a dam. The turbinesare connected to a generator that changes kinetic energyinto electrical energy.
Wind EnergyWind is caused by the sun’s heating of Earth’s surface.Because Earth’s surface is not heated evenly, wind iscreated. The kinetic energy of wind can turn the bladesof a windmill. Wind turbines are shown in Figure 6. Awind turbine changes the kinetic energy of the air intoelectrical energy by turning a generator.
renewable resource a natural resourcethat can be replaced at the same rate atwhich the resource is consumed
Figure 5 This dam converts theenergy from water going downstreaminto electrical energy.
Figure 6 These wind turbinesare converting wind energy intoelectrical energy.
vv--------------------------------------a
The Ozone Layer Have studentsresearch and prepare a presenta-tion about the importance ofthe ozone layer of the atmo-sphere and the effects of ozonelayer depletion on the environ-ment and on solar energy.Students should answer thefollowing questions: “Howmight the amount of thermalenergy received from the sunbe affected? How do holes inthe ozone layer affect the effi-ciency of solar energy as anenergy resource?” Encouragestudents to be creative in theirpresentations. l Logical
Oil from Shale and Tar SandsIt is estimated that Earth hasreserves of shale oil and tarsands that are about 500 timeslarger than the known crude-oilreserves. Shale oil and tar sandscould provide the world withpetroleum products long aftercrude oil reserves have beenexhausted. However, the produc-tion of petroleum from shale oiland tar sands is much moreexpensive than the productionof crude oil is. Have studentsdebate whether resources shouldbe spent to produce petroleumfrom shale oil and tar sands orto develop renewable energyresources. l Interpersonal
Of the total energy used by a standardincandescent light bulb, only one-tenthis converted to light energy. The rest isconverted to thermal energy. That’s whylight bulbs are so hot after they havebeen on for a while!
SUPPORT FOR
English Language LearnersTypes of Energy Resources To helpstudents assimilate all the informationpresented in this section, ask them tocreate T-charts for each type of energyresource as they read. T-charts should in-clude the advantages and disadvantagesof each type of energy. When studentshave finished their charts, ask them toshare what they have written to makea class T-chart for each type of energyresource. As a class, discuss the accuracyof the chart. Discuss the “best” type ofenergy.l Verbal/Interpersonal Section 4 • Energy Resources 261
Geothermal EnergyThermal energy caused by the heating of Earth’s crust is calledgeothermal energy. Some geothermal power plants pump waterunderground next to hot rock. The water returns to the surfaceas steam, which can then turn the turbine of a generator.
✓✓Reading Check Where does geothermal energy come from?
BiomassPlants use and store energy from the sun. Organic matter,such as plants, wood, and waste, that can be burned to releaseenergy is called biomass. Figure 7 shows an example. Somecountries depend on biomass for energy.
The Two Sides to Energy ResourcesAll energy resources have advantages and disadvantages. Howcan you decide which energy resource to use? Table 1 comparesseveral energy resources. Depending on where you live, whatyou need energy for, and how much energy you need, oneenergy resource may be a better choice than another.
Figure 7 Plants capture the sun’senergy. When wood is burned, itreleases the energy it got fromthe sun, which can be used togenerate electrical energy.
Table 1 Advantages and Disadvantages of Energy Resources
Energy Resource Advantages Disadvantages
Fossil fuels • provide a large amount of thermalenergy per unit of mass
• are easy to get and transport• can be used to generate electricity and
to make products such as plastic
• are nonrenewable• produce smog• release substances that can cause acid
precipitation• create a risk of oil spills
Nuclear • is a very concentrated form of energy• does not produce air pollution
• produces radioactive waste• is nonrenewable
Solar • is an almost limitless source of energy• does not produce pollution
• is expensive to use for large-scaleenergy production
• is practical only in sunny areas
Water • is renewable• does not produce air pollution
• requires dams, which disrupt ariver’s ecosystem
• is available only where there are rivers
Wind • is renewable• is relatively inexpensive to generate• does not produce air pollution
• is practical only in windy areas
Geothermal • is an almost limitless source of energy• power plants require little land
• is practical only in areas near hot spots• produces wastewater, which can
damage soil
Biomass • is renewable• is inexpensive
• requires large areas of farmland• produces smoke
Reteaching -------------------------------------bRenewable and NonrenewableChallenge the class to nameeach energy resource mentionedin this section. Prompt studentsto tell whether each resource isrenewable or nonrenewable andwhy. l Logical
1. Explain the process of fossil-fuel formation. (Organisms thatlived millions of years ago diedand were covered by layers ofsediment. The pressure and thetemperatures produced by theoverlying layers caused chemicalreactions that changed theorganic matter into fossil fuel.)
2. Name the five types ofenergy that are consideredrenewable resources. (solarenergy, energy from water, windenergy, geothermal energy, andbiomass)
When Fossil Fuels Run Out Askstudents to think about how lifewill change when fossil fuels runout. How will the environment,jobs, travel, sports, and industrybe affected? Ask students towrite or illustrate a short storythat describes a day in such atime. l Verbal
Answer to Reading Check
Geothermal energy comes from thethermal energy given off by undergroundareas of hot rock.
262 Chapter 9 • Energy and Energy Resources
For a variety of links related to thischapter, go to www.scilinks.org
Choosing the Right Energy ResourceAs Table 1 shows, each source of energy that we know abouton Earth has advantages and disadvantages. For example, youhave probably heard that fossil fuels pollute the air. They willalso run out after they are used up. Even renewable resourceshave their drawbacks. Generating lots of energy from solarenergy is difficult. So it cannot be used to meet the energyneeds of large cities. Geothermal energy is limited to the “hotspots” in the world where it is available. Hydroelectric energyrequires large dams, which can affect the ecology of riverlife. Energy planning in all parts of the world requires carefulconsideration of energy needs and the availability and respon-sible use of resources.
• An energy resource is anatural resource that canbe converted into otherforms of energy in orderto do useful work.
• Nonrenewable resourcescannot be replaced afterthey are used or can bereplaced only after longperiods of time. Theyinclude fossil fuels andnuclear energy.
• Renewable resourcescan be replaced innature over a relativelyshort period of time.They include energyfrom the sun, wind,and water; geothermalenergy; and biomass.
• The sun is the source ofmost energy on Earth.
• Choices about energyresources depend onwhere you live and whatyou need energy for.
Using Key Terms
1. In your own words, write a defi-nition for the term fossil fuel.
Complete each of the following sen-tences by choosing the correct termfrom the word bank.
nonrenewable resourcesrenewable resources
2. There is a practically limitlesssupply of .
3. are used up more quicklythan they are being replaced.
Understanding Key Ideas
4. Which of the following is arenewable resource?
a. windb. coalc. nuclear energyd. petroleum
5. Compare fossil fuels andbiomass as energy resources.
6. Trace electrical energy back tothe sun.
Critical Thinking
7. Making Comparisons Describethe similarities and differencesbetween transforming energy ina hydroelectric dam and a windturbine.
8. Analyzing Ideas Name anenergy resource that does NOTdepend on the sun.
Interpreting Graphics
9. Use the pie chart below toexplain why renewable resourcesare becoming more important tothe United States.
Topic: Energy ResourcesSciLinks code: HSM0515
Review
Earth’s EnergyResources Find
examples of places in theworld where the variousenergy resources mentionedin this chapter are used. Listthem in your science journal.Discuss any patterns that younotice, such as which regionsof the world use certainenergy resources.
Oil
Other
Nuclear
U.S. Energy Sources
Naturalgas
Coal
Answers to Section Review
1. Sample answer: fuel fromdecomposed organic matterfrom plants and animals thatlived millions of years ago
2. renewable resources3. nonrenewable resources4. a5. Both fossil fuels and biomass
come from organic matter, areburned to generate energy, andcause air pollution when used.Biomass is renewable, whereasfossil fuels are nonrenewable.
6. Sample answer: Electricalenergy comes from powergenerators, which may berun by burning fossil fuels, whichcarry stored energy from the sunharnessed in plants and animals.(Other answers are possiblebased on other methods of gen-erating electricity, includingwind, solar, and biomass.)
7. A hydroelectric dam and a windturbine both harness renewablesources of energy. Neithercauses air pollution. However, ahydroelectric dam can disruptriver life, whereas a wind turbinehas hardly any effect on theenvironment.
8. Possible answers includegeothermal and nuclear energy.
9. The pie chart indicates that non-renewable resources currentlyrepresent a large portion of U.S.energy sources. This use of fos-sil fuels, which are nonrenew-able, for such a large proportionof its energy may make theUnited States run out of fossilfuels. Therefore, renewableresources will become increas-ingly important in the future.
Interactive Explorations CD-ROM• The Generation Gap
CRF
Section 4 • Energy Resources 263
LabSkills PracticeUsing Scientifi c Methods
Form a hypothesis aboutwhere kinetic energy comesfrom.
Test your hypothesis bycollecting and analyzing data.
• books (2 or 3)
• masking tape
• meterstick
• metric balance
• rolling cart
• stopwatch
• wooden board
Finding EnergyWhen you coast down a hill on a bike or skateboard, youmay notice that you pick up speed, or go faster and faster.Because you are moving, you have kinetic energy—the energy ofmotion. Where does that energy come from? When you pedalthe bike or push the skateboard, you are the source of thekinetic energy. But where does the kinetic energy come fromwhen you roll down a hill without making any effort? In thislab, you will find out where such kinetic energy comes from.
Ask a Question
1 Where does the kinetic energy come from when you roll downa hill?
Form a Hypothesis
2 Write a hypothesis that is a possible answer to the questionabove. Explain your reasoning.
Test the Hypothesis
3 Copy the Data Collection Table below.
OBJECTIVES
Data Collection Table
Height oframp (m)
Length oframp (m)
Mass ofcart (kg)
Weight ofcart (N)
Time of trial (s) Averagetime (s)1 2 3
MATERIALS
DO NOT WRITE IN BOOKO NOT WRITE IN BOOK
Skills PracticeSkills Practice LabLab
Finding Energy
Teacher’s NotesTeacher’s Notes
Time RequiredTwo 45-minute class periods
Lab Ratings
rTeacher Prep f
Student Set-Up f
Concept Level fff
Clean Up f
M A T E R I A L SThe materials listed for this lab areenough for each group of 2–3 stu-dents. Rolling carts are availablefrom suppliers of science classroommaterials. The ramp should be atleast 1 m long.
Procedure NotesUse one day to set up andcollect data. Use the second dayfor calculations, or assign thecalculations as homework.
Ask a Question
1. Sample answer: The kineticenergy comes from the potentialenergy that you had at the top ofthe hill.
Form a Hypothesis
2. Accept all testable hypotheses.
CHAPTER RESOURCES
Chapter Resource File
CRF • Datasheet for Chapter Lab• Lab Notes and Answers
Technology
Classroom Videos• Lab Video
• Energy of a PendulumRebecca Ferguson
North Ridge Middle SchoolNorth Richland Hills, Texas
Holt Lab Generator CD-ROMSearch for any lab by topic, standard, difficulty level,or time. Edit any lab to fit your needs, or create yourown labs. Use the Lab Materials QuickList softwareto customize your lab materials list.
CLASSROOM
TESTED& APPRO
VED
264 Chapter 9 • Energy and Energy Resources
4 Use your books and board to make a ramp.
5 Use masking tape to mark a starting line atthe top of the ramp. Be sure the starting line isfar enough down from the top of the ramp toallow the cart to be placed behind the line.
6 Use masking tape to mark a finish line at thebottom of the ramp.
7 Find the height of the ramp by measuring theheight of the starting line and subtracting theheight of the finish line. Record the height ofthe ramp in your Data Collection Table.
8 Measure the distance in meters between thestarting line and the finish line. In the DataCollection Table, record this distance as thelength of the ramp.
9 Use the balance to find the mass of the cart ingrams. Convert this measurement to kilogramsby dividing it by 1,000. In your Data CollectionTable, record the mass in kilograms.
0 Multiply the mass by 10 to get the weight ofthe cart in newtons. Record this weight in yourData Collection Table.
q Set the cart behind the starting line, andrelease it. Use a stopwatch to time how longthe cart takes to reach the finish line. Recordthe time in your Data Collection Table.
w Repeat step 11 twice more, and average theresults. Record the average time in your DataCollection Table.
Analyze the Results
1 Organizing Data Copy the Calculations Tableshown at right onto a separate sheet of paper.
2 Analyzing Data Calculate and record thequantities for the cart in the Calculations Tableby using your data and the four equations thatfollow.
Final speed � 2 � average speed(This equation works because the cart acceler-ates smoothly from 0 m/s.)
(Remember that 1 kg • m²/s² � 1 J, the unitused to express energy.)
Gravitational potential energy �
weight � height(Remember that 1 N � 1 kg • m/s²,so 1 N � 1 m � 1 kg • m²/s² � 1 J)
Draw Conclusions
3 Drawing Conclusions How does the cart’sgravitational potential energy at the top of theramp compare with its kinetic energy at thebottom? Does this support your hypothesis?Explain your answer.
4 Evaluating Data You probably found that thegravitational potential energy of the cart at thetop of the ramp was almost, but not exactly,equal to the kinetic energy of the cart at thebottom of the ramp. Explain this finding.
5 Applying Conclusions Suppose that whileriding your bike, you coast down both a smallhill and a large hill. Compare your final speedat the bottom of the small hill with your finalspeed at the bottom of the large hill. Explainyour answer.
average speed �length of rampaverage time
kinetic energy �2
mass � (final speed)2
Calculations Table
Averagespeed(m/s)
Finalspeed(m/s)
Kineticenergy atbottom (J)
Gravitational potential
energyat top (J)
DO NOT WRITE IN BOOKO NOT WRITE IN B
Draw Conclusions
3. The magnitude of the cart’sgravitational potential energyat the top of the ramp is nearlyidentical to the magnitude ofits kinetic energy at the bottomof the ramp. Whether thisfinding supports the originalhypothesis will depend on theoriginal hypothesis.
4. The cart’s gravitational potentialenergy at the top of the rampis slightly greater than its kineticenergy at the bottom of the rampbecause some of the energyis used to do work against fric-tion. Without friction, the twoenergy measurements wouldbe the same.
5. You would have a greater finalspeed at the bottom of the largehill than at the bottom of thesmall hill. The amount of gravita-tional potential energy dependson the height of the startingposition. Starting from a greaterheight means starting with moregravitational potential energy,which is converted into kineticenergy as you coast downthe hill.
Labs You Can Eat• Power-Packed Peanutsb• Now You’re Cookingb
Long-Term Projects & Research Ideas• Great Balls of Firea
Calculator-Based Labs• Power of the Suna• Solar Homesa
Chapter 9 • Chapter Lab 265
For each pair of terms, explain how the meanings of the terms differ.
1potential energy and kinetic energy
2mechanical energy and energyconversion
3 friction and the law of conservation of energy
4 renewable resources and nonrenewable resources
5 energy resources and fossil fuels
Multiple Choice
6 Kinetic energy depends on
a. mass and volume.b. velocity and weight.c. weight and height.d. velocity and mass.
7 Gravitational potential energy depends on
a. mass and velocity.b. weight and height.c. mass and weight.d. height and distance.
8Which of the following types of energy is not a renewable resource?
a. wind energyb. nuclear energyc. solar energyd. geothermal
energy
9 Which of the following sentences describes a conversion from chemical energy to thermal energy?
a. Food is digested and used to regulate body temperature.
b. Charcoal is burned in a barbecue pit.c. Coal is burned to produce steam.d. All of the above
0 When energy changes from one form to another, some of the energy always changes into
a. kinetic energy.b. potential energy.c. thermal energy.d. mechanical energy.
Short Answer
q Name two forms of energy, and relate them to kinetic or potential energy.
w Give three examples of one form of energy being converted into another form.
e Explain what a closed system is, and how energy is conserved within it.
r How are fossil fuels formed?
Math Skills
t A box has 400 J of gravitational potential energy.
a. How much work had to be done to give the box that energy?
If the box weighs 100 N, how far above the ground is it?
UNDERSTANDING KEY IDEAS
USING KEY TERMS
266 Chapter 9 • Energy and Energy Resources
5. Sample answer: Energy resources are natural sources of energy that can be converted into other forms of energy to do useful work. Fossil fuels are energy resources that come from decayed organic matter from plants and animals that lived millions of years ago.
Understanding Key Ideas6. d7. b8. b9. d
10. c
11. Sample answer: Thermal energy depends partly on the kinetic energy of the particles that make up an object. Chemical energy is a kind of potential energy because it depends on the arrangement of atoms in a molecule, which is energy of position.
12. Sample answer: When a person jumps off a diving board, his or her potential energy is converted into kinetic energy. When steam turns the blades of a turbine, the thermal energy of the steam is converted into the kinetic energy of the moving turbine.
ANSWERS
Using Key Terms1. Sample answer: Potential
energy is the energy of position of an object. Kinetic energy is the energy of motion of an object.
2. Sample answer Mechanical energy is the total kinetic and potential energy of an object. Energy conversion is the change of energy from one form to another.
3. Sample answer: Friction is a force that opposes motion between two surfaces that are in contact. The law of conser-vation of energy states that energy is never created or lost; it simply changes form.
4. Sample answer: Renewable resources are replaced natu-rally more quickly than they are used up. Nonrenewable resources are not replaced—or are replaced very slowly—after they are used up.
Assignment GuideSECTION QUESTIONS
1 1, 6, 11, 15, 17, 23–25
2 2, 7, 9–10, 12, 16, 18, 20
3 3, 13, 21–22
4 4–5, 8, 14, 19
yConcept Mapping Use the following terms to create a concept map: energy, machines, sound energy, hair dryer, electrical energy, energy conversions, thermal energy, and kinetic energy.
uApplying Concepts Describe what hap-pens in terms of energy when you blow up a balloon and release it.
i Identifying Relationships After you coast down a hill on your bike, you will eventually come to a complete stop. Use this fact to explain why perpetual motion is impossible.
oPredicting Consequences Imagine that the sun ran out of energy. What would happen to our energy resources on Earth?
pAnalyzing Processes Look at the photo below. Beginning with the pole vaulter’s breakfast, trace the energy conversions necessary for the event shown to take place.
aForming Hypotheses Imagine two cars, one of which is more efficient than the other. Suggest two possible reasons one car is more efficient.
sEvaluating Hypotheses Describe how you would test the two hypotheses you proposed in item 21. How would you determine whether one, both, or neither hypothesis is a factor in the car’s efficiency?
Use the graphic below to answer the questions that follow.
dWhat is the skier’s gravitational potential energy at point a?
fWhat is the skier’s gravitational potential energy at point b?
gWhat is the skier’s kinetic energy at point b? (Hint: mechanical energy �potential energy � kinetic energy)
500 N
5 m
10 m
CRITICAL THINKING
INTERPRETING GRAPHICS
a
b
When a hair dryer is turned on, electricalenergy is converted into kinetic energy ofthe turning fan and thermal energy of thehot coils inside the hair dryer.
13. Within a closed system, objects transferenergy only to each other. Energy is con-served in a closed system because energyonly changes form and is neither creatednor destroyed.
14. Fossil fuels formed from decayed organicmatter of plants and animals, which wassubjected to millions of years of pressureunder Earth’s crust.
15. a. 400 Jb. 400 J � 100 N � 4 m
Critical Thinking16. An answer to this
exercise can befound at the endof this book.
17. The compression of the air inthe balloon is a kind of potentialenergy, which is released in theform of kinetic energy whenyou let the balloon go.
18. As the potential energy you hadon top of the hill is convertedinto kinetic energy, some of thekinetic energy is converted tothermal energy because of fric-tion, so you eventually come toa stop. In the same way, per-petual motion is impossiblebecause energy conversionsalways result in energy being“lost” as heat.
19. We would no longer have asource of solar, wind, or hydro-electric energy.
20. The food that the pole vaulterate for breakfast containedchemical energy, which hisbody turned into a different kindof chemical energy, which wasthen used as kinetic energywhen he pole-vaulted.
21. Sample answer: One car maybe more aerodynamic than theother, causing less energy to belost because of friction. One carmay have fewer moving partsthan the other does, causingless energy to be lost becauseof friction. (Other answers,including a difference inweight, are possible.)
22. Sample answer: To test theeffect of aerodynamics, mea-sure the efficiency of a slowercar that has the more aerody-namic design and compareit with the efficiency of aslower car that has the lessaerodynamic design. (Answersshould include controlledexperiments.)
Interpreting Graphics23. 500 N � 10 m � 5,000 J24. 500 N � 5 m � 2,500 J25. 5,000 J � 2,500 J � 2,500 J
CHAPTER RESOURCES
Chapter Resource File
• Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg
Workbooks
Study Guide• Study Guide is also available in Spanish.
CRF
Chapter 9 • Chapter Review 267
READINGRead each of the passages below. Then, answer the questions that follow each passage.
Passage 1 Gas hydrates are icy formations of water and methane. Methane is the main component of natural gas. The methane in gas hydrates is made by bacteria in the ocean. Large areas of hydrates have been found off the coasts of North Carolina and South Carolina in marine sediments. In just two areas that are each about the size of Rhode Island, scientists think there may be 70 times the amount of natural gas used by the United States in 1 year. The energy from gas hydrates could be used to drive machinery or generate electrical energy.
1. How large are each of the two gas hydrate deposits mentioned in this article?
A about the size of the United StatesB about the size of South CarolinaC about the size of North CarolinaD about the size of Rhode Island
2. What are gas hydrates mainly made of?
F bacteria and sedimentsG water and methaneH natural gas and waterI ice and sediments
3. How long could U.S. natural gas needs be met by all the gas in both deposits mentioned?
A 1 yearB 2 yearsC 70 yearsD 140 years
4. Where do methane gas hydrates come from?
F ocean waterG bacteriaH sedimentsI ice
Passage 2 Two new technologies may reduce the price of electric cars. One is called a hybridelectric vehicle. This vehicle has a small gasoline engine that provides extra power and recharges the batteries. The other technology uses hydro-gen fuel cells instead of batteries. These cells use the hydrogen present in more-conventional fuels, such as gasoline or ethanol, to produce an electric current that powers the car.
1. In this passage, what does vehicle mean?
A electricB hybridC carD current
2. Which of the following are conventional fuels?
F gasoline and ethanolG hydrogen and ethanolH gasoline and hydrogenI only hydrogen
3. Which of the following is a fact in this passage?
A A hybrid electric vehicle runs partly on gasoline.
B All electric cars are hybrid.C All electric cars use hydrogen fuel cells.D Hydrogen fuel cells use conventional fuel.
4. What do the two new technologies described in the passage have in common?
F They do not use conventional fuels.G They may reduce the price of electric cars.H They use hybrid engines.I They use hydrogen to produce an electric
current.
268 Chapter 9 • Energy and Energy Resources
READING
MISCONCEPTIONALERT
Passage 21. C2. F3. A4. G
Question 3: Answer D may be chosen by students if they incorrectly infer from the last sentence of the passage that hydrogen is a conventional fuel.
Passage 11. D2. G3. C4. G
Question 3: Students may misread the passage to say that there is 70 times the amount of natural gas used by the United States in 1 year in each of the two gas deposits mentioned and so may choose answer D.
Answers to the standardized test preparation can help you identify student misconcep-tions and misunderstandings.
Teacher’s NoteTeacher’s NoteTo provide practice under more realistic testing conditions, give students 20 minutes to answer all of the questions in this Standardized Test Preparation.
Stand
ardized
Test Prep
aration
1. According to the graph, the United States relies on fossil fuels for about what percentage of its energy?
A 30%B 45%C 60%D 80%
2. Nuclear energy represents about what percentage of U.S. energy sources?
F 15%G 30%H 50%I 70%
3. Which energy source accounts for about 25% of U.S. energy?
A oilB coalC natural gasD nuclear energy
1. Gerald bought 2.5 kg of apples. How many grams of apples did he buy?
A 0.0025 gB 0.25 gC 25 gD 2,500 g
2. Which group contains ratios that are equivalent to 3/8?
3. Carmen went to a bookstore. She bought three books for $7.99 each and four books for $3.35 each. Which number sentence can be used to fi nd c, the total cost of the books?
A c � 3 � (7.99 � 1) � (4 � 3.35)B c � (1 � 7.99) � (3 � 3.35)C c � (3 � 7.99) � (4 � 3.35)D c � (3 � 7.99) � (4 � 3.35)
4. Rhonda’s Mobile Car Washing charges $15 to wash a customer’s car. Vacuuming the car costs an extra $10. Rhonda wants to know how much money she earned last week. When she looks at her appointment book, Rhonda fi nds that she washed a total of 50 cars. Only 20 of these cars were vacuumed after being washed. How much money did Rhonda earn last week?
F $500G $750H $950I $1050
The pie chart below shows U.S. energy use by source of energy. Use the chart below to answer the questions that follow.
Read each question below, and choose the best answer.
INTERPRETING GRAPHICS MATH
Oil
Other
Nuclear
U.S. Energy Sources
Naturalgas
Coal
Chapter 9 • Standardized Test Preparation 269
INTERPRETING GRAPHICS1. D2. F3. B
Question 1: Correctly answering this question requires a recognition that oil, coal, and natural gas are fos-sil fuels. According to the pie chart, together they constitute about 80% of U.S. energy sources.
MATH1. D2. F3. C4. H
Question 4: Rhonda earned $950: $750 from 50 cars being charged $15 each for a wash, plus $200 for 20 of the cars being charged $10 each for a vacuum.
CHAPTER RESOURCES
Chapter Resource File
CRF • Standardized Test Preparation g
State Resources
For specifi c resources for your state, visit go.hrw.com and type in the keyword HSMSTR.
in Action
in Action
MathThe speed of light is approximately300,000,000 m/s. How much energy isequivalent to the mass of 0.00000002 gof hydrogen?
Social Studies
Scientific DiscoveriesE � mc²The famous 20th-century scientist AlbertEinstein discovered an equation that isalmost as famous as he is. That equation isE � mc². You may have heard of it before.But what does it mean?
The equation represents a relationshipbetween mass and energy. E representsenergy, m represents mass, and c representsthe speed of light. So, E � mc² means thata small amount of mass has a very largeamount of energy! Nuclear reactors harnessthis energy, which is given off when radioac-tive atoms split.
Science, Technology,
and SocietyUnderwater Jet EnginesAlmost all boats that have engines usepropellers. But in 2002, a British companyannounced that it had developed an under-water jet engine.
The underwater jet engine works byproducing steam in a gasoline-poweredboiler. When the steam hits the water, itcondenses to a very small volume, whichcreates a vacuum. This vacuum causes thrustby sucking in water from the front of thetube. The underwater jet engine is extremelyenergy-efficient, produces a great amount ofthrust, and creates very little pollution.
Research the kinds of water propulsionpeople have used throughout history.Note which kinds were improvements onprevious technology and which werecompletely new.
Science, Technology,
and Society
Discussion --------------------------------- GENERAL
Have students name differentkinds of water-propulsiontechnology that people haveused over the ages. Oars, sails,and propellers should be dis-cussed, and students should rec-ognize that each is a differentkind of technology. Draw stu-dents’ attention to the designfeatures of the underwater jetengine, and ask students tostate the similarities and differ-ences between the underwaterjet engine and propellers. Havestudents offer opinions aboutwhether the underwater jetengine is a completely new tech-nology or an improvement onthe propeller design.
Scientific Discoveries
BackgroundEinstein’s famous equation stat-ing the equivalence of mass andenergy was a direct result of histheory of special relativity. Thetheory and implications of rela-tivity were his life’s work, andthe results of that work havebeen confirmed by numerousexperiments.
Answer to Social Studies Activity
Oars were a very early—and probably thefirst—technology to be used in water propul-sion. Later boat designs utilized long rows ofoars on either side of the ship. Sails, which har-ness wind power, have also been used sinceancient times. Sail technology progressed froma single sail to a series of different types of sailson a single ship. With the industrial age andthe steam engine came paddleboats and thenpropellers.
Answer to Math Activity
2 � 10–8 g � 2 � 10–11 kg(2 � 10–11 kg) � (3 � 108 m/s)2 �(2 � 10–11 kg) � (9 � 1016 m/s) � 1,800,000 J
270 Chapter 9 • Energy and Energy Resources
Language Arts
Look up the word energyin a dictionary. Compare the different definitions you find to the definition given in this chapter.
Cheryl MelePower-Plant Manager Cheryl Mele is the manager of the Decker Power Plant in Austin, Texas, where she is in charge of almost 1 billion watts of electric power generation. Most of the electric power is generated by a steam-driven turbine system that uses natural gas fuel. Gas turbines are also used. Together, the systems make enough electrical energy for many homes and businesses.
Cheryl Mele says her job as plant manager is to do “any-thing that needs doing.” Her training as a mechanical engi-neer allows her to run tests and to find problems in the plant. Previously, Mele had a job help-ing to design more-efficient gas turbines. That job helped prepare her for the job of plant manager.
Mele believes that engineer-ing and power-plant manage-ment are interesting jobs because they allow you to work with many new technologies. Mele thinks young people should pur-sue what interests them. “Be sure to connect the math you learn to the science you are doing,” she says. “This will help you to under-stand both.”
To learn more about these Science in Action topics, visitgo.hrw.com and type in thekeyword HP5ENGF.
Check out Current Science®
articles related to this chapter by visiting go.hrw.com. Just type in the keyword HP5CS09.
Chapter 9 • Science in Action 271
Careers
Background Cheryl Mele earned a bachelor of science degree in mechanical engineering. She worked as a programmer for General Electric, became interested in power-plant design, and joined a General Electric design group. Mele worked as a mechanical engineer for Austin Energy, where her diverse experiences made her the top choice for plant manager. Students should be familiar with the general principles of the generation of electrical energy, including the use of various fuel sources (steam from coal, natural gas, or nuclear energy) to power a turbine .
Teaching Strategy-- GENERAL
As an extension of the investi-gation, students can find ways to use less electrical energy to minimize their impact on the environment.
Answer to Language Arts Activity
Other definitions may mention “force” or “power” or mention a “capacity for action.” Such definitions are similar to, but not as explicit and exact as, the definition given in this book.
