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Informational Text • Pro/Con
Grade 5
Lexile 970L
Learning A–Z level
Word Count 1,809
Multi-level N/A
Refer to the Focus Question on page 2 of this title to guide
discussion and support additional learning connected to the text.
Z
Energy Sources: The Pros and Cons informs readers
about the major sources of energy consumed in the world
today: fossil fuels, hydroelectric energy, solar and wind
energy, and nuclear power. Discussions of the pros and
cons of each source are included, allowing readers to form
their own opinion about the use of each type of energy.
Photographs, charts, and diagrams accompany the text.
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ENERGY SOURCES:
THE PROS AND CONS
Written by David L. Dreier
ENERGY SOURCES:
THE PROS AND CONS
[Word count: 215]
ENERGY SOURCES:
THE PROS AND CONS
Written by David L. Dreier
Words to Know
energy
environmentalists
fossil fuels
global
hydroelectric
pollutants
sediment
turbines
Focus Question
What impact does the production of
energy have on Earth’s environment?
[Word count: 36]
3
Table of Contents
The Endless Need for Energy . . . . . . . . . . . . . . . . 4
Fossil Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Hydroelectric Power . . . . . . . . . . . . . . . . . . . . . . . 10
Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Nuclear Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Looking to the Future . . . . . . . . . . . . . . . . . . . . . 20
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Energy Sources: The Pros and Cons4
The Endless Need for Energy
The United States is a modern society . Like all
modern societies, it uses a lot of energy . Scientists
define energy as the ability to do work .
Many kinds of things can be called work .
Getting an automobile to move down a road or
an airplane to
fly is work, and
so is producing
electricity or
running the
machinery
in a factory .
The energy
used by the
United States
and other
modern
societies comes
from many
sources . Much
of it comes from
the burning of fuels, such as coal and gasoline .
Other energy comes from the power of flowing
water, from the light of the Sun, the wind, or from
the splitting of atoms .
Machines in this car factory need energy to
build cars.
[Word count: 390]
5
Energy Use in the United States, 1949–2005
YearConsumptionProductionImportsExports
194931.9831.721.451.59
195034.6235.541.911.47
195540.2140.152.792.29
196045.0942.84.191.48
196554.0250.685.891.83
197067.8463.58.342.63
197169.2962.729.532.15
197272.763.9211.392.12
197375.7163.5814.612.03
197473.9962.3714.32.2
19757261.3614.032.32
197676.0161.616.762.17
19777862.0519.952.05
197879.9963.1419.111.92
197980.965.9519.462.86
198078.2867.2315.83.69
198176.3467.0113.724.31
198273.2966.6111.864.61
198373.1564.1511.753.69
198476.7968.8912.473.79
198576.5867.7611.784.2
198676.8367.1314.154.02
198779.2267.6115.43.81
198882.8768.9817.34.37
19898569.4118.774.66
199084.7370.7918.824.75
199184.6770.4318.335.14
199286.017019.374.94
199387.6568.3321.274.26
199489.2970.7222.394.06
199591.271.1322.264.51
199694.2372.4723.74.63
199794.872.4625.224.51
199895.272.8426.584.3
199996.8471.7127.253.71
200098.9871.2928.974.01
200196.571.9130.163.77
200297.9770.8629.413.67
200398.2770.1431.064.05
2004100.4170.3933.544.43
200599.8969.1734.264.64
Consumption
Production
Imports
Exports
Quadrillion BTU
The United States uses more
energy than it produces.
What does this tell you
about the energy future of
the United States?
All energy sources have their pros and cons—
their good points and bad points . Modern societies
have to make many decisions about how best
to produce energy . The needs of the society have
to be balanced against the need to protect the
environment . These choices are not always easy
to make .
SOURCE: U.S. Energy Information Administration, Annual Energy Review 2005
Energy Use in the United States, 1949–2005
The United States uses more energy
than it produces. What does this tell
you about the energy future of the
United States?
Energy Sources: The Pros and Cons6
Fossil Fuels
Fossil fuels—coal, oil, and natural gas—are a
leading energy source around the world . They are
called fossil fuels because they were formed from
the remains of plants and animals that died many
millions of years ago . Over time, great heat and
pressure underground changed the remains into
materials we use as fuel .
About 85
percent of energy
used each year in
the United States
comes from fossil
fuels . Coal is
burned in many
power plants to
produce electricity .
Fuels made from
oil—such as
gasoline, diesel
fuel, and jet fuel—
power our cars,
trucks, and
airplanes . Most
homes use natural
gas to provide
power for stoves and water heaters .
Gasoline is a common fossil fuel.
[Word count: 300]
7
1
2
3
4
Marine plants and animals die and sink to the ocean floor. They mix with dirt and sand to form a sediment layer.
Time passes, more layers are added, pressure builds, and the buried plant and animal material changes to kerogen while the sediment forms into sedimentary rock.
More time, more layers, and more pressure change the kerogen into oil, which begins to rise through tiny holes in the sedimentary rock.
Oil rises until it hits rock it can’t pass through. Oil rigs drill through this rock to pump out the collected oil.
How Oil Forms
Energy Sources: The Pros and Cons8
One of the main
advantages of fossil
fuels is that they are abundant—found in many
places and in large amounts . In addition, they
contain a lot of usable energy . Coal is especially
abundant . The United States has enough coal to
last another 200 to 300 years .
A special advantage of natural gas is that it
burns very cleanly . When natural gas burns, it
produces mostly carbon dioxide and water vapor .
Oil’s main advantage is that it burns
efficiently—meaning that little is wasted in the
change to energy . Also, the refining process that
produces gasoline and diesel fuel produces other
petroleum products used in crayons, bubble gum,
eyeglasses, and even artificial heart valves .
A pump jack
is used for
extracting
petroleum
from an
oil well.
A close-up
of coal
[Word count: 242]
9
All fossil fuels are essentially nonrenewable
energy sources because nature cannot create
enough to keep up with demand . Many experts
think that the world’s oil wells will be empty in a
few decades . But, even before then, the oil supply
will be too small to meet global demands .
Also, fossil fuels (except for natural gas)
produce pollutants . Cars, factories, and many
power plants release harmful chemicals into the
air . Since fossil
fuels are
burned, air
pollution will
continue to be
a problem .
Another
problem is
called the
greenhouse effect . Gases released from burning
fossil fuels trap more heat in Earth’s atmosphere
than would be trapped naturally . This heating up
of Earth’s atmosphere is called global warming .
Scientists think carbon dioxide contributes most
to worsening the greenhouse effect, so even
natural gas adds to the problem .
Pollutants rise into the atmosphere.
Energy Sources: The Pros and Cons10
Hydroelectric Power
Water is widely used to produce electricity .
You might wonder how electricity can be
produced using water . The answer is by building
dams . A dam is a huge, wide wall, usually made
of concrete . It is built across a river to hold back
the river’s flow . The river’s water then fills up
a large area behind the dam, forming a lake
or reservoir .
Water from the lake is released through the
bottom of the dam . The water moves very fast .
It passes through big machines called turbines .
Fanlike blades inside the turbines spin when
water rushes through them . The turbines are
connected to other machines, called generators,
making them spin too .
Inside a generator, a shaft is surrounded by
giant magnets . All around the shaft and magnets
is a huge coil of wire . When the turbines spin
the shafts and magnets of the generators, they
move electrons in the coil of wire . The movement
of these electrons creates an electric current .
Electricity made at dams is called hydroelectric
power . Hydro is a prefix (first part of a word) that
means water .
[Word count: 358]
11
penstock
turbine
generator
power lines
dam
reservoir
Generators inside a dam
How a Dam Works
Water from the reservoir flows into
the penstock. As the water rushes
downward, it turns the blades of the
turbine before emptying into the river.
Energy Sources: The Pros and Cons12
Dams produce a great deal of needed
electricity . There are more than 2,000 hydroelectric
dams in the United States . They produce about
10 percent of the nation’s
electricity . Hydroelectric
dams produce about 20
percent of the world’s
electricity .
Dams have many
other uses too . They
prevent flooding by
storing the water
from heavy rain and
snowmelt, and gradually
releasing it later .
Dams also create many opportunities for
recreation, such as boating and fishing in the
lakes they create . In addition, the lakes provide
water for homes and industries as well as provide
water for farmers to irrigate their crops during
drier times of the year .
Hoover Dam blocks the Colorado
River, creating Lake Mead, one of
the world’s largest artificial lakes.
Lake Mead’s boat docks
[Word count: 180]
13
Flood prevention is good for people, but not
so good for the environment . Rivers are supposed
to flood . Flooding produces sediment, which is
a mixture of gravel, sand, and topsoil . Sediment
deposited by floods keeps the soil rich in
farmlands located near rivers . When a river is
dammed, it cannot renew the soil on the land
around it .
Dams also block the route for fish that
swim up and down rivers . In the U .S . Pacific
Northwest, dams have been a serious problem
for salmon . Every three to five years, salmon
swim from the ocean up rivers to their birthplaces
to lay eggs . Dams make it difficult for salmon to
swim up and down rivers . As a result, salmon
populations have severely declined in the past
100 years .
Salmon swimming upstream
Energy Sources: The Pros and Cons14
Solar Energy
Sunlight carries huge amounts of energy . You
can feel the Sun’s energy when sunlight warms
your skin on a summer day . To capture the Sun’s
energy, scientists have developed solar cells,
called photovoltaic (FOE-toe-vole-TAY-ik) cells .
These cells convert sunlight into electricity .
When sunlight hits a solar cell, the cell absorbs
some of the light energy . Particles in the solar cell
move faster, and the movement of these particles
creates electricity .
In some places,
large panels of
solar cells harvest
sunshine to
make electricity
for homes and
businesses . Solar
cells have been
placed on cars and
appliances, too .
A solar panel is used to
provide energy to this
phone booth.
[Word count: 268]
15
A solar heat collector uses the Sun’s energy to
heat water . These solar heat collectors are often
placed on rooftops . Water circulates through
pipes in the panels, and the Sun’s radiant energy
heats the water . The heated water is pumped into
a building through more pipes . The heat leaves
the water and heats the inside of the building .
Then the cooled water returns to the rooftop to be
heated again .
This solar water heater is one of many used to heat water for a town.
Energy Sources: The Pros and Cons16
In some areas of the world, such as the
southwestern United States, there are many
sunny days . In these places, solar cells and
solar panels can produce lots of electricity and
heat . Since the Sun sends abundant free energy
streaming toward Earth 24 hours a day, people
in many parts of the world, not just the sunniest
places, have mounted solar cells and solar panels
on the roofs of their houses or businesses to lower
their energy costs .
Experts say that huge installations of solar
panels in sunny regions could generate enough
electricity to supply an entire country . Capturing
this energy can help overcome our diminishing
energy supply . New ways to capture this energy
are being developed all the time to maximize
efficiency .
Rooftop solar panels provide this house with energy.
[Word count: 235]
17
There are two main problems with solar cells .
One is that they are very expensive to manufacture .
Their cost makes hydroelectric and fossil-fuel
power plants a cheaper source of energy . Until
inexpensive manufacturing is developed for solar
cells, this free energy source will continue to come
at a high cost to capture and convert to electricity .
The second problem is that not all areas of the
world get abundant sunlight . Other sources of
energy would be needed as a backup to the solar
cells, which adds to overall energy costs .
Some people who live near houses that use
solar cells and solar panels think the rooftop
systems are ugly . They believe the look of the solar
systems will decrease the value of their homes .
Power plants could serve as backups for solar farms.
Energy Sources: The Pros and Cons18
Nuclear Power
Nuclear power plants unlock the energy inside
atoms to generate electricity . Each splitting of an
atom releases energy . An atomic bomb explodes
by creating a very rapid chain reaction . A nuclear
power plant uses the radioactive element uranium
to create a slow, controlled chain reaction .
The energy released by breaking apart uranium
atoms is used to heat water into steam . The steam
is then used to generate electricity in much the
same way that coal power plants produce it .
Cooling towers keep the core of a nuclear power plant at a safe temperature.
[Word count: 249]
19
Uranium releases an incredible amount of
energy . One kilogram (2 .2 lbs) of uranium can
produce more energy than 3 million kilograms
(6 .6 million lbs) of coal . Nuclear power plants
have another advantage over coal power plants:
They do not produce gases that can pollute the
skies or add to global warming .
Many people oppose nuclear power because
of its dangers . One danger is the possibility of
an accident . A nuclear power plant can’t explode
like an atomic bomb . However, it can have a
steam explosion if the core (the area containing
the uranium) gets too hot . This would spew out
a lot of dangerous radiation . A second danger is
the waste material nuclear power plants produce .
Even when uranium is no longer useful for
generating electricity, it is still highly radioactive .
It remains dangerous for thousands of years .
Nuclear waste is handled very carefully.
Energy Sources: The Pros and Cons20
Looking to the Future
In years to come, we will have to find
substitutes for oil . Hydroelectric power may also
be replaced, too . Many people are concerned
about the environmental effects of dams and
would like to see many dams torn down . The
use of solar energy will probably continue to
grow . Energy experts also say that more nuclear
power plants will have to be built to meet
growing energy needs .
Wind turbines could provide more energy in the future.
[Word count: 249]
World Energy Use and Creation by Region, 2004
RegionProduction, in quadrillion
BTUs
Consumption, in
quadrillion BTUs
North, Central, and South
America
126143
Europe51 86
Eurasia67 45
Middle East62 21
Africa32 14
Asia and Oceania105 138
Past and Estimated Future Energy Use by Type, 1980–2030
YearOilCoalNatural GasRenewables
(wind, solar, etc.)
Nuclear
1980132.178.753.920.77.6
1981126.879.053.921.18.5
1982123.980.554.121.79.5
1983122.282.655.123.010.7
1984123.486.460.823.513.0
1985123.589.463.423.815.3
1986127.090.564.224.216.3
1987129.394.167.624.117.7
1988133.496.971.024.919.2
1989135.096.974.225.419.8
1990136.195.975.125.920.4
1991136.492.876.726.521.2
1992137.390.377.126.521.3
1993136.290.379.127.822.0
1994138.990.879.028.122.4
1995141.693.481.329.523.3
1996146.195.483.230.124.1
1997148.193.983.730.423.9
1998149.993.484.430.424.3
1999153.193.886.531.025.1
2000156.798.789.631.525.7
2001157.999.889.931.126.4
2002158.796.895.932.226.7
2003162.1100.499.132.726.5
2010185.6128.8121.145.228.9
2015199.1144.4139.849.131
2020210.8160.1156.153.132.9
2025224.3176.7172.557.834
2030239.1195.5189.962.434.7
21
Three regions of the world use more energy than they create. Why do you
think that is the case? Where do these regions find their extra energy sources?
Using current rates as a guide, this chart shows the growth in the world’s
energy use between now and the year 2030. Experts project that oil will not
be available in the decades to come. What does this chart and information
tell you about energy use in the future?
North, Central,
and South America
EuropeEurasiaMiddle
East
AfricaAsia and
Oceania
ProductionConsumption
160
120
80
40
0
–
–
–
–
–
138
126
143
51
86
67
45
62
21
32
14
105
Quadrillion BTU
World Energy Use and Creation by Region, 2004
Past and Estimated Future
Energy Use by Type, 1980–2030
SOURCE: U.S. Energy Information Administration, International Energy Outlook 2006
250
200
150
100
50
0
19801980200320152030
Oil
Coal
Natural Gas
Nuclear
Renewables
(wind, solar, etc.)
HistoryProjections
Quadrillion BTU
Energy Sources: The Pros and Cons22
Scientists are also researching other ways to
generate energy, such as using wind turbines
or geothermal energy . Wind turbines generate
electricity when their blades turn in the wind .
The turbines require no fuel and don’t create
pollution, but they are huge and can kill local
birds . Geothermal energy comes from deep
underground where the Earth is very hot . Water
can be circulated down into the ground in pipes
to absorb that heat . The hot water can then be
used to heat homes and buildings . However, in
many areas, the underground heat can be difficult
and expensive to reach .
Geothermal plant
[Word count: 350]
23
Countries Creating the Most Energy in 2004
• United States: 70 .4
• China: 56 .0
• Russia: 51 .7
• Saudi Arabia: 24 .2
• Canada: 18 .6
• Iran: 12 .1
• I ndia: 11 .1
• Nor way: 10 .8
• Australia: 10 .6
• Mexico: 10 .3
01020304050607080
United
States
Quadrillion BTU
China
Russia
Saudi
Arabia
Canada
Iran
India
Norway
Australia
Mexico
70.4
56.0
51.7
24.2
18.6
12.1
11.1
10.8
10.6
10.3
Two things are certain . We need energy, and
the fossil fuels that supply most of our energy
will not last forever . Finding renewable
alternatives is key to the world’s energy future .
Scientists will continue to do research . Each new
source of energy will have its pros and cons .
Governments, businesses, and environmentalists
will continue to debate which energy sources are
best while our need for energy continues to grow .
Countries Creating the Most Energy in 2004
Energy Sources: The Pros and Cons24
Glossary
energy (n.) page 4
different types of power that people and machines need to
do work
environmentalists (n.) page 23
people concerned with keeping Earth’s ecosystems healthy
fossil fuels (n.) page 6
energy sources taken from the earth, including coal, oil,
and natural gas
global (n.) page 9
the worldwide rise of temperatures warming through air
pollution trapping heat
hydroelectric (adj.) page 10
produced from water as a source of electricity
pollutants (n.) page 9
harmful chemicals that damage the environment
sediment (n.) page 13
bits of earth carried by flooding
turbines (n.) page 10
wheels that spin when the force of water, air, or steam
is applied
Index
carbon dioxide, 8, 9
coal, 4, 6–9, 18, 19, 21
dams, 10–13, 20
floods, 12, 13
fossil fuels, 6–9, 23
gasoline, 4, 6, 8
geothermal, 22
global warming, 9, 19
hydroelectric, 10–12, 17
kerogen, 7
natural gas, 6, 8, 9, 21
nuclear (atom ic), 18, 19, 21
oil, 6–9, 20, 21
pollution, 9, 22
solar, 14–17, 20
steam, 18, 19
Sun, 4, 14–17
uranium, 18, 19
water, 4, 6, 10–13, 15, 18, 22
wind, 20–22
[Word count: 350] | Chalk