FOCUS ON EARTH SCIENCE (17)

Earth’s resources provide materials and energy for >ˆ˜Ê`i> People use a variety of materials from different parts of Earth to meet a diverse range Earth’s natural resources can be used f

584

This is a field of crops that can eventually be used for energy This energy source—called biodiesel—can be made from vegetable oils or animal fats According to the National Biodiesel Board, as many as 250 school districts nationwide use biodiesel for their buses.

Earth’s resources provide

materials and energy for

>ˆ˜Ê`i> People use a

variety of materials from

different parts of Earth

to meet a diverse range

Earth’s natural resources

can be used for energy,

usually through

resources can help

pre-vent shortages and

reduce pollution

6.b, 6.c, 7.c

6.a, 6.b, 6.c, 7.a, 7.d, 7.e

6.a, 6.b, 7.b, 7.e

Visit to:

▶ view

▶ explore Virtual Labs

▶ access content-related Web links

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Start-Up Activities

585

Where did that

come from?

Look around your classroom

Do you know what materials

are used to make objects you

use? Where did the materials

come from?

Procedure

1 On a blank sheet of paper, draw a table

with three columns—one for objects, one

for materials, and one for original source

2 Name five or six items in your classroom

each made of a different material

3 List the main material you think is used

to make each item

4 Guess the original source of the material

for each item

Think About This:

• Determine if it is obvious that some

items are made from natural materials,

such as wood

• List the items you think might be made

from oil or petroleum products

STEP 1 Fold the bottom of a horizontal

sheet of paper up about 4 cm

STEP 2 Fold in half.

STEP 3 Unfold once and dot with glue

or staple to make two pockets Label as

shown

'LUE

,i˜iÜ>Li œ˜Ài˜iÜ>Li

Renewable and Nonrenewable Make the following Foldable to show the differences between renewable and

nonrenewable resources

Analyzing

As you read this chapter, use note cards to list natural and material resources Explain why each resource is considered renewable

or nonrenewable Collect your note cards

in the appropriate pocket

6.c

ca6.msscience.com

ELA6: R 2.4

Learn It! Knowing how to find answers

to questions will help you on reviews and tests Some

answers can be found in the textbook, while other

answers require you to go beyond the textbook These

answers might be based on knowledge you already have

or things you have experienced.

Practice It! Read the excerpt below

Answer the following questions and then discuss them

with a partner.

Most of us use natural energy resources each day without thinking about it For example, you might awaken to an electric alarm clock, turn on the lights, and take a hot shower You might listen to a radio as you eat pancakes cooked on a natural gas stove You arrive at school on a bus and enter a classroom heated

by oil or electricity Before the school day even starts, you depended on many energy resources

—from page 612

Questions and Answers

Apply It! Look at some tions in the text Which questions can be answered directly from the text? Which require you to go beyond the text?

ques-• Can you name six ways you used energy resources today?

• What processes do you think were used to bring those resources to

your home or school?

• What effect does using energy resources have on the environment?

Target Your Reading

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

1 Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

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

you’ve changed your mind about any of the statements

• If any of your answers changed, explain why

• Change any false statements into true statements

• Use your revised statements as a study guide

1 Items you use every day, such as clothes, books, and food, come from Earth’s resources

2 Nonrenewable resources are replaced faster than they can be used

3 Water is a renewable resource because it moves through cycles on Earth

4 Fossil fuels formed millions of years ago from cayed plants and animals

5 Oil is the most abundant fossil fuel on Earth

6 Most of our energy comes from solar power and wind because the energy can be readily stored for later use

7 Energy sources other than fossil fuels have not been fully developed because they cause pollution

8 Most plastic is made from oil

Before You Read

swer in t he chapter This w

ill help y ou rememb er what

LESSON 1

Figure 1 Everything on this shelf

is made of natural materials on Earth.

Identify which products are from plant

material Which are from animals?

Organic resourcesNatural resources are materials and energy sources that

are useful or necessary to meet the needs of Earth’s isms, including people Plants and animals that are living,

organ-or were alive at sometime in the past, are organ-organic material resources Think about your food Nearly all of it is either animal or plant material How many items like those in

Figure 1 come from plants or animals? Some of your clothes, such as denim jeans, are made from cotton plants Wool, silk, and leather come from animals Many buildings are made of wood and most home furnishings are manu-factured from plant materials All of these are made from organic material resources

Reading Guide

What You’ll Learn

▼Identify material resources

used by people to meet

their basic needs and to

make their lives more

comfortable.

▼Give examples of material

resources used to make

common objects.

▼Classify Earth’s material

resources as renewable or

nonrenewable.

Why It’s Important

Understanding Earth’s natural

resources will help you use

6.b Students know different natural

energy and material resources, including air,

soil, rocks, minerals, petroleum, fresh water,

wildlife, and forests, and know how to

classify them as renewable or nonrenewable.

6.c Students know the natural origin of

the materials used to make common objects.

7.c Construct appropriate graphs from

data and develop qualitative statements

about the relationship between variables.

Lesson 1 • Natural Resources 589

Inorganic resources

Not all natural resources are from plants or

animals Inorganic material resources, which

include metals and minerals, do not come

from organisms Gold, boron, calcium

car-bonate, granite, and lanthanides are mined

and exported to other countries from

Cali-fornia You are probably familiar with how

gold is used Boron is used in agriculture,

detergents, ceramics, glass, fiberglass, wood

treatments, and as a fire retardant Calcium

carbonate is used in paper, plastics, industry,

agriculture, and food, and it has many other

uses Granite is used for making roads and

building materials Lanthanide products are

used in cellular phones, televisions,

comput-ers, and transportation systems

Name two examples of inorganic material resources.

Mining Costs A large amount of a mineral

must be in one place to make it worth the

cost of the mining operation If the deposits

are too small, it would cost more to separate

the metal or minerals from the earth than

what the materials are worth The price of

natural resources varies and so does the cost

of the equipment to find and extract the

resources Throughout history, sometimes it

was worthwhile to mine a particular resource

and other times it was impractical to extract

the same resource

Building Structures Other inorganic

re-sources include industrial and building

mate-rials, like those shown in Figure 2 Steel is

made from iron that is extracted from Earth

Sand and gravel may not seem very valuable,

but they are important resources for

construc-tion Sand is used to make concrete that

pro-vides strength and stability to buildings,

side-walks, bridges, and other structures Sand and

gravel production in California is worth more

than $1 billion each year This is much more

than the value of gold mined in the state

Building Bridges Sand and Gravel

Figure 2 Iron ore, sand, and gravel are important inorganic resources used for construction.

Determine which inorganic resource is used to

make the steel structure in the bridge.

Iron Mining

590 Chapter 14 • Resources

Renewable Resources

Earth’s material resources that are capable

of being replaced by nature as quickly as it is

being used are called renewable natural

resources Some renewable resources include

trees, food resources and animal resources

Using up Renewable Resources

You might think that renewable resources will always be available for human use But even renewable resources can be used up if

we do not manage them carefully For ple, Douglas fir trees in California are used for lumber These trees might be over

exam-200 years old when they are cut down It can

be difficult to manage such slow-growing renewable resources if they can’t be replaced

as fast as they are cut Some trees do grow faster and the populations of these trees are easier to manage

Explain how trees can be a able resource.

renew-Habitats as a Resource

Resources are more than the products that you use For instance, a chicken needs food and water and protection from predators in order to become food for you The whole habitat becomes a resource

Forest Habitat Think about other resources

that might be affected when cutting trees Roads must be built to allow heavy machines into forested areas to cut trees Road-building, cutting trees, and hauling them out of the forest can destroy forest habitat Although young trees are usually planted to replace those that are lost, the forest habitat might not

be completely replaced In this case, the forest habitat is not a renewable resource The trees are a renewable resource, they can replenish themselves The habitat that a mature forest provides—food, shelter, and mates—is not a renewable resource It would take more than a lifetime to replace the interactions

How old is that tree?

Trees have adaptations that help them

stay healthy and allow them to live a very

long time Do you think there is a

correla-tion between the age and the height of a

tree?

Data

1 Read the following facts about

Califor-nia trees and arrange them in a table.

• Ponderosa pines grow to 50 m and

can live 125 years.

• Sequoias grow to 95 m and can live

2 Graph the tree heights.

3 Graph how long each tree can live.

Data Analysis

1 Interpret from your graph which trees

live the longest.

2 Give examples of uses you think

humans might have for these trees.

3 Infer which trees might not be

consid-ered a renewable resource.

6.b, 7.c

Lesson 1 • Natural Resources 591

Estuary Habitat When the rate of fish caught

exceeds the rate of fish reproduction, this

important renewable resource is affected But

fish populations can also decrease if areas the

fish need for growth and reproduction are

destroyed An estuary, like the one in Figure 3,

is a fertile area where a river meets an ocean

Estuaries contain a mixture of freshwater and

salt water Many species of fish and other

organ-isms use estuaries to breed and raise their young

because the calm waters and abundant food

sources are ideal for young But the ocean and

its harbors are important resources for humans,

too Goods are transported by ships into

har-bors The beautiful ocean view makes coastal

areas ideal for marinas, houses, and hotels

Habitat Loss In Colonial times, wetlands

occupied more than 890,312 km2 of the lower

48 states By 1983, just 415,034 km2 remained

This represents less than half the original

wet-lands In California, 90 percent of wetlands have

been developed In fact, the San Francisco bay

area alone has lost 85 percent of its wetlands

For fish species that depend on estuaries, the

numbers of young fish that hatch each year and

grow into adults decline as their nursery areas

are destroyed Many bird species depend on

these coastal wetland habitats, too

Effects of Habitat Loss Estuaries aren’t the

only areas in danger Populations of many

organisms in California and the United States

are declining in numbers California has nearly

300 threatened and endangered plant and

animal species Most of these declining numbers

are due in some way to habitat loss Not all of

these species are resources used directly by

humans You learned in Chapter 13 that plants

and animals are interconnected through food

webs A decrease in the population of one

species whose habitat has been destroyed might

have negative effects on species that serve as

resources for people For example, humans eat

fish that are caught off the coast Lost habitat

means lost resources

Estuary

Developed Harbor

Figure 3 Estuaries are important ing and breeding grounds They are also attractive places to live and work

nest-Describe how development in estuaries can

affect populations of adult fish.

Nonrenewable Resources

Resources that are used more quickly than they can be

replaced by natural processes are called nonrenewable

natu-ral resources Some nonrenewable resources are used at rates

far faster than their geologically slow formation rates For example, gold, a nonrenewable resource, is deposited when hot water and molten rock, called magma, flows through spaces in underground rock The hot magma heats water and gold travels with mineral solutions in the water When the magma and solution cools, gold collects

How is gold deposited in rocks?

Gold is extracted from two types of mines in California, shown in Figure 4 Because gold is removed from Earth much faster than it can be deposited, it is a nonrenewable natural resource Gold is worth a lot of money because it can easily can be formed into various shapes, it is pleasing to look at, and there is a limited amount of it on Earth

California Gold Rush

In 1848, large veins of gold were discovered in California Within months, thousands of people were traveling across the country in hopes of striking it rich The gold seekers were called “49ers” because most left home in 1849 The California gold rush was a world attraction—gold seekers from all over the world flocked to California

Although gold was easy to find at first, it quickly became difficult to make money because the mines yielded less and less gold Those who did find gold often spent it on all the basic necessities of life The people who made the most money were those who supplied the gold miners with food and other goods and services

Figure 4 Gold can be

dislodged from rock

through erosion Placer

mines are used to

sepa-rate this gold from the

rocks Large veins are

also taken from

Table 1 Average Water Use

Watering the lawn or plants with a hose 30 L/min

Lesson 1 • Natural Resources 593

Water

Recall from Chapter 13 that water moves through cycles,

evaporating from Earth’s surface and condensing into clouds

in the atmosphere Water then returns to Earth’s surface

through precipitation All the water on Earth is already here

Currently, there is no way to create new water Freshwater is

an important nonrenewable resource for California Even

though most of California is arid and dry, people use large

amounts of water for irrigation, industry, and personal use

Most of the large soft-drink bottles hold two liters Imagine

how many liters of water you use for each activity in Table 1

Table 1 Estimate how much water your family uses every day

California gets some of its freshwater from the Colorado

River Water from the lower Colorado River is divided

between Arizona, California, Nevada, Native Americans, and

Mexico Many state and federal laws, as well as treaties with

Mexico have been passed to try to regulate the use of this

water resource As states in the Colorado basin have increased

their use of the river’s water, there is concern about how long

the Colorado River can be relied on as a water source One

way to solve this problem is to reuse water Water that has

been reclaimed from municipal wastewater, called sewage,

can be treated and reused

regulate (REH gyuh layt)

(verb) to control or direct

according to rule, principle, or law

Stoplights help regulate traffic flow.

LESSON 1 Review

What have you learned?

Earth has many natural resources that we have learned to use to manufacture materials Renewable resources are those that can be replaced as quickly as they are used Resources that are used faster than they can be replaced are nonrenew-able You will learn in the next section how some of Earth’s natural resources are used for energy As you read, think about how we can conserve natural resources without increasing our use of energy resources

Create your own lesson

summary as you organize

an outline

1 Scan the lesson Find and

list the first red main

heading.

2 Review the text after

the heading and list 2–3

details about the heading.

3 Find and list each blue

subheading that follows

the red main heading.

4 List 2–3 details, key terms,

and definitions under

each blue subheading.

5 Review additional red

main headings and their

supporting blue

subhead-ings List 2–3 details about

each.

ca6.msscience.com

Standards Check

Using Vocabulary

1 Materials and energy sources

used to meet the needs of Earth’s organisms are

Understanding Main Ideas

3 Label the following natural resources as either renewable

or nonrenewable: silver, ton, diamonds, fish, gravel,

change bird populations 6.b

6 Compare Create a chart like the one below to compare renewable and nonrenewable

Renewable Resources

Nonrenewable Resources

7 Deduce how renewable resources could become

Applying Science

8 Recommend a plan to save freshwater during the next week Describe the steps and provide the amount of water you would save on the

Figure 5 Use of fossil fuels has increased since 1950.

Use Graphs How many more tons of fuel were used in 2000 than in 1970?

Lesson 2 • Energy Resources 595

Szent-Fossil Fuels Fossil fuels are fuels formed in Earth’s crust over hun-

dreds of millions of years Fossil fuels are nonrenewable resources because they cannot form as fast as they are used Coal, oil, and natural gas are fossil fuels Cars, buses,

trains, and airplanes are powered by gasoline, diesel fuel, and jet fuel, which are made from oil Coal is used in many power plants to produce electricity Natural gas is used in manufacturing, for heating and cooking, and sometimes as

a vehicle fuel People on Earth are using more fossil fuels for energy today than they did in 1950, as shown in Figure 5

Reading Guide

What You’ll Learn

▼Compare and contrast

the development and

extraction of fossil fuels.

▼List the energy resources

that are used to create

steam to turn turbines.

▼Assess the advantages and

disadvantages of each

energy resource.

Why It’s Important

People use vast amounts of

energy resources daily.

6.a Students know the utility of energy

sources is determined by factors that are

involved in converting these sources to

useful forms and the consequences of the

conversion process.

6.b Students know different natural

energy and material resources, including air,

soil, rocks, minerals, petroleum, freshwater,

wildlife, and forests, and know how to

classify them as renewable or nonrenewable.

7.b Select and use appropriate tools and

technology (including calculators, computers,

balances, spring scales, microscopes, and

binoculars) to perform tests, collect data, and

display data.

7.e Recognize whether evidence is

consistent with a proposed explanation.

Generator

Magnet

596 Chapter 14 • Resources

Energy from Fossil Fuels

The most useful energy sources can be readily converted to heat, electricity, and transportation Today, people use fossil fuels as the primary source for energy because existing

technologies readily convert energy from fossil fuels into

forms we can use Fossil fuels contain a lot of stored energy and burn easily to heat water and make steam The steam then is used to turn large turbines that power generators, like the one in Figure 6, to create electricity

Formation of Fossil Fuels

Fossil fuels are made from decayed plants and animals that have been preserved in Earth’s crust by pressure, bacterial processes, and heat This means that fossil fuels are organic natural resources About 300 million years ago, before the age

of the dinosaurs, Earth was covered with green, leafy plants

Earth’s oceans and freshwater contained a large amount of algae and other small organisms Over many hundreds of years, the decaying organisms were covered by sand and clay

The sand and clay layers formed into rock

What are fossil fuels made from?

As more rock was formed, the weight pressed down on the trapped remains of organisms Eventually, over millions of years, heat and pressure from layers of rock pressing down the plant and animal remains turned them into the three main forms of fossil fuels—coal, oil, and natural gas—as shown in Table 2

technology (tek NAH luh

jee)

(noun) the application of

sci-ence, especially for industrial

or commercial use

Communication technology has

help develop cellular telephones.

Figure 6 Most power plants use turbine generators to produce electricity

Explain what causes the turbine blades to turn.

Table 2 Formation of Fossil Fuels

Oil Formation

Microscopic plants and bacteria are the main source of oil.

1 Some of these organisms were producers,

using energy from the Sun to make food for growth and reproduction When they died, they fell to the seafloor.

2 The microscopic organisms were buried

under clay.

3 Many layers of clay and mud increased the

pressure and temperature, forming liquid oil.

2 The partially decayed plant material, called

peat, becomes sandwiched between layers

of sediment

3 Soft coal forms under moderate pressure

and heat

4 As more heat and pressure are applied, the

soft coal becomes hard coal

Natural Gas Formation

Natural gas forms along with oil

1 Because it is less dense than oil, natural gas

is usually found above oil deposits

2 At low temperatures, more oil is produced

relative to natural gas At higher temperatures, however, more natural gas is created, as opposed to oil Natural gas is usually associated with oil in deposits that are 1–3 km below Earth’s crust

3 Natural gas is found in areas beneath layers

of solid rock The rock prevents the gas from escaping to the surface.

Lesson 2 • Energy Resources 597

598 Chapter 14 • Resources

Oil

Oil, sometimes called petroleum, is used for heating and can be refined into gasoline, kerosene, or diesel fuel As you will read later in this chapter, petroleum is also used for many other every day materials

Oil formed mainly from ancient, microscopic plants and bacteria that lived in the ocean and saltwater seas When these organisms died, they were quickly buried by clay and did not completely decay but formed muds rich in materials that form fossil fuels The temperature and pressure increased

as more clay and mud collected on top of the dead organisms Further increases in temperature and pressure caused liquid oil to form The oil flowed into spaces and pools in the rock

To get the oil out of the rock spaces, geologists drill wells deep into Earth to the level of the reservoir of oil, as shown in

Figure 7 Most of this oil is under pressure, so it flows to the surface, where it is collected Oil collected out of the ground

is sometimes called crude oil Crude oil must be refined for use in cars, large trucks, airplanes, and trains

Figure 7 How is oil extracted from Earth?

Natural Gas

Natural gas forms along with oil Because it is less dense, it most often is found on top of oil pools Natural gas is valu-able because it burns cleanly and can be transported easily in underground pipelines Natural gas is used in many ways, such as for heating homes and cooking food

Coal

Coal is the most abundant fossil fuel in the world Coal forms where plant matter collects but is prevented from com-plete decay The partially decayed plant material forms layers

of spongy material called peat Over time, the peat becomes buried and compressed Increased pressure and temperature produce a solid, sedimentary rock known as coal

Coal developed under moderate amounts of heat and sure is called soft coal If more heat and pressure is applied to soft coal, it can become hard coal Soft coal retains some moisture and sulfur When soft coal burns, it can release pollutants into the air Hard coal is the cleanest-burning coal and has the greatest amount of carbon, so it provides more energy than soft coal Coal is removed from Earth by strip mining and underground mining

pres-Figure 7 Oil is found

deep within Earth’s crust

Drill rigs can be located

on land or in the ocean.

Figure 9 Underground mines must be supported

by beams and pillars Miners must be protected from polluted air

Figure 8 Coal near Earth’s surface can be extracted by stripping away the land surface.

Strip Mines In strip mining, shown in Figure 8, large

machinery is used to scrape the plants, soil, and rock layers

off the ground above a vein of coal Machines remove the

surface of Earth, including the trees and other organic

mate-rial, and place it beside the mine Once the layer of coal is

exposed, it can be broken apart and loaded into containers

for transportation Strip mining is cost-effective if the coal is

close to the surface

Underground Mines If the coal is deeper, underground

mines, like the one in Figure 9, are used instead of strip

min-ing Underground mines are created by digging down into

the earth at an angle to form tunnels These tunnels go

deeper and deeper until they reach the coal Wooden beams

and pillars are used to support the tunnel and make it safe

for the miners In some mines, tracks are laid to allow

wagons to roll along the tunnels to move the coal toward

the surface

Mining coal produces a fine, black coal dust If miners

inhale coal dust, their lungs can be damaged In the past,

many miners suffered from a disease, called black lung

Today, miners wear protective clothing and masks to avoid

inhaling coal dust

Why do underground coal miners need to wear masks?

600 Chapter 14 • Resources

Alternatives to Fossil Fuels

Generating electricity doesn’t have to come from burning fossil fuels Alternative energy sources, including water, wind, ocean waves, and natural heat sources beneath Earth’s sur-face can be used to produce electricity

Hydroelectric power is a renewable energy source Large dams block the flow of water from major rivers and create lakes behind the dams As the water moves rapidly through the narrow openings in the dam, turbines generate electricity More water can be released when needs are great

Scientists are searching for cost-effective ways of harnessing energy from wind to generate enough energy to power local communities Near Palm Springs, California, wind farms with long rows

of wind towers connect to generators This polluting, renewable method has proven success-ful on a small scale Wind towers require a steady wind that is not too strong or too weak The lack of consistent wind, however, prevents it from being reliable as a sole source of electricity

Have you ever seen pictures of volcanoes? Perhaps you have visited a geyser spewing hot water In some places on Earth, the magma is near Earth’s surface The heat energy in Earth’s crust is called

geothermal energy The extreme heat found near

geysers and volcanoes can be used to generate steam for electricity Geothermal energy is clean, renewable, and safe, but there are only a few places where sufficient heat is near enough to the surface

Can you explain why these alternative energy resources are renewable? Because water moves through cycles driven by solar energy, hydro-electric power is a renewable resource Can wind

be used up as it turns a turbine? Geothermal energy is renewable because magma supplies a continuous source of heat

3 Geothermal Energy

2 Wind Energy

1 Hydroelectric Power

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Figure 10 Nuclear reactors rely on fission to generate heat Heated

water turns to steam that turns a turbine to generate electricitỵ

Describe what is happening in this illustration.

Lesson 2 • Energy Resources 601

Nuclear Energy

All matter is made of atoms—tiny particles that we cannot

seẹ Even though atoms are very small, when they split, a

large amount of energy is released Splitting atoms to release

energy is called nuclear fission Atoms from uranium, an

ele-ment that is mined from ore deposits in Earth, are split in a

nuclear reactor, like the one in Figure 10 When atoms split,

the energy that is released heats water in the reactor Steam is

produced and turns a turbinẹ The turbine runs a generator

that creates electricitỵ

How is nuclear fission used to generate electricitỷ

Combining atoms also generates heat In a nuclear fusion

reaction, two atoms of hydrogen that are heavier than

normal, called deuterium, join together to form one atom It’s

the same type of reaction that powers the Sun Like nuclear

fission, nuclear fusion gives off large amounts of energỵ

Fusion reactions, however, are not easy to start Have you

ever tried to make the same ends of a magnet join together?

Like the ends of a magnet, an atom’s center has a positive

chargẹ In order to get the atoms to fuse and start the fusion

reaction, temperatures must be over 100,000,000°C

Very little uranium is needed to supply a nuclear fission

reactor; however, uranium is a nonrenewable resourcẹ

Deu-terium can be made from water, which you learned is

nonre-newable if not managed well

S CIENCE U SE V C OMMON U SE reaction

Science Use a change or

transformation in which

a substance decomposes

or combines with other

substances Sugars are made from carbon dioxide and water

in a photosynthesis reaction

Common Use a response to a

stimulus Poison ivy can cause

a severe skin reaction.

WORD ORIGIN

fission

from Latin fissionem; means a

breaking up, cleaving

602 Chapter 14 • Resources

Solar Energy

Sunlight is a perpetual renewable resource because we can never use up all the energy from the Sun Solar energy converts the light and heat energy from the Sun into electricity Solar cells capture energy from the Sun and convert it to energy for calculators and other small appliances Solar panels are made

up of many solar cells and store the energy in

a series of batteries for later use For solar energy to be effective for larger-scale use, there must be a way to harness large amounts

of energy from the Sun

Solar Generated Power Have you ever

noticed that it is hotter near the ceiling or on the upstairs level of a house? This is because warm air rises Scientists in California are experimenting with panels constructed at the bottom of large towers, like the one in

Figure 11, that collect sunlight and heat up

As the warm air rises, it turns turbines that generate electricity Solar energy is a possibility for a clean, endless supply of energy in the future We just need to develop reliable, cost-effective ways to get large amounts of energy from the Sun and store that energy for later use Figure 12 shows other ways solar energy is harnessed

How does a solar tower generate electricity?

Drawbacks of Solar Power The Sun seems

like the perfect source of clean energy

Currently though, solar energy is not effective because the equipment is expensive, the batteries store a limited amount of energy, and solar panels do not collect energy at night

cost-or on very cloudy days Solar energy is not a practical way to power cars and trucks The weight of the batteries required to store the energy would use additional energy to trans-port These added batteries would take up much needed space in a small car

Figure 11 Science and engineering are

exciting careers because there are so many

new ideas to investigate This is a new

design to use the energy of the Sun for

Lesson 2 • Energy Resources 603

Visualizing Solar Energy

▲ Power Plants In California’s Mojave Desert, an experimental solar power plant used hundreds

of mirrors to focus sunlight on a water-filled tower The steam pro- duced by this system generates enough electricity to power 2,400 homes.

▼ Electricity Photovoltaic (PV) cells turn

sun-light into electric current They are commonly

used to power small devices, such as

calcula-tors Panels that combine many PV cells provide

enough electricity for a home—or an orbiting

satellite, such as the International Space

Station, shown below.

▼ Cooking In hot, sunny

weather, a solar oven or

panel cooker can be used

to cook a pot of rice or

heat water The powerful

solar cooker shown below

reaches even higher

tem-peratures It is being used

to fry food. ▲ Water Heating Water is heated

as it flows through small pipes in this roof-mounted solar heat col- lector The hot water then flows into an insulated tank for storage.

▼ Indoor Heating South-facing windows and heat-absorbing construction materials turn a room into a solar collector that can help heat an entire building, such as this Connecticut home.

Figure 12

Sunlight is a renewable energy source that

provides an alternative to fossil fuels Solar

technologies use the Sun’s energy in many

ways—from heating to electricity generation.

Contributed by National Geographic

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604 Chapter 14 • Resources

Biomass

Organic matter that makes up plants is known as biomass Biomass can be used to produce fuels for electricity and transportation Food crops, like corn and soybeans, grasses, trees, and even garbage are forms of biomass However, most biomass must be converted, or refined, into usable energy forms While there are many petroleum refineries today that convert oil into many different types of fuels and materials, there are few refineries for biomass

What is biomass?

Wave Energy

Have you ever tried to stand up in the ocean when the waves were crashing over you? If so, you have experienced the energy of the waves Harnessing the energy from the waves is challenging It is difficult to find a location with regular, strong wave action, where a system of turbines would not be damaged on the rocks, and where it would work during low and high tides

Total Energy Contributions

Figure 13 shows that in the United States, about 40 percent

of energy use is from oil, 23 percent is from coal, 22 percent from natural gas, 8 percent from nuclear energy, and 3 per-cent from hydroelectric power The rest is from a combina-tion of geothermal, solar, and wind energy

Figure 13 Both renewable

and nonrenewable resources

are used for energy in the

United States

Calculate how much energy

comes from fossil fuels.

LESSON 2 Review

Lesson 2 • Energy Resources 605

What have you learned?

Billions of people all over the world use fossil fuels every

day Because fossil fuels are nonrenewable, Earth’s supply of

them is limited In the future, they might become more

expensive and difficult to obtain You will learn in the next

chapter how using fossil fuels can cause environmental

prob-lems Developing alternative energy resources, such as wind

and solar power, can help reduce pollution and conserve

Create your own lesson

summary as you write a

newsletter

1 Write this lesson title,

number, and page

num-bers at the top of a sheet

of paper

2 Review the text after

the red main headings

and write one sentence

about each These will be

the headlines of your

newsletter

3 Review the text and write

2–3 sentences about each

blue subheading These

sentences should tell who,

what, when, where, and

why information about

each headline.

4 Illustrate your newsletter

with diagrams of

impor-tant structures and

pro-cesses next to each

headline

ca6.msscience.com

Standards Check

Using Vocabulary

1 In your own words, write the

definition of fossil fuels 6.b

2 The heat energy in Earth’s

crust is called 6.a

Understanding Main Ideas

3 List three types of fossil

4 Complete the concept map

about alternative fuels 6.a

alternative fuels include

5 Summarize the effect on the environment from extracting

fossil fuels 6.a

6 Illustrate how oil forms 6.b

7 Why is solar energy not

in the United States 6.a

9 Rank the energy resources in order of risk to the natural environment Explain your

ELA6: W 1.2