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2. Changing Forms of Energy
 Chemical, thermal, radiant, and electrical are
some of the forms that energy can have.
 In the world around you, energy is transforming
continually between one form and another.
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3. Changing Forms of Energy
 Forest fires are a dramatic example of an
environmental change that can occur naturally as a
result of lightning strikes.
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4. Tracking Energy Transformations
As the mountain biker
pedals, his leg muscles
transform chemical energy
into kinetic energy.
Kinetic energy of his leg
muscles transforms into
kinetic energy of the bicycle
as he pedals.
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5. Tracking Energy Transformations
Some of this energy
transforms into potential
energy as he moves up the
hill.
Also, some energy is
transformed into thermal
energy.
His body is warmer
because chemical energy is
being released
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6. Tracking Energy Transformations
Because of friction, the
mechanical parts of the
bicycle are warmer, too.
Thermal energy is almost
always produced by an
energy transformation.
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7. Tracking Energy Transformations
Because of friction, the
mechanical parts of the
bicycle are warmer, too.
The energy transformations that occur
Thermal energy is almost
when people exercise, when cars run,
always produced by an
when living things grow and even
when stars explode, all energy transformation.
produce
thermal energy.
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8. Law of Conservation of Energy
 Energy is never created or destroyed.
 The only thing that changes is the form in which energy
appears.
Example: When the biker is resting at the summit, all his
original energy is still around. Some of the energy is in the
form of potential energy, which he will use as he coasts down
the hill. Some of this energy was changed to thermal energy
by friction in the bike. Chemical energy was also changed to
thermal energy in the biker’s muscles, making him feel hot As
he rests, this thermal energy moves from his body to the air
around him. No energy is missing--- it can all be accounted
for.
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9. Potential energy is converted into kinetic energy.
 Before the yo-yo begins its fall it
has stored energy due to its
position. At the top it has its
maximum potential energy. As it
starts to fall the potential energy
begins to be changed into kinetic
energy. At the bottom its
potential energy has been
converted into kinetic energy so
that it now has its maximum
kinetic energy.
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10. Potential energy is converted into kinetic energy.
A waterfall has both potential
and kinetic energy. The water
at the top of Bridal Veil Falls
has stored potential energy.
When the water begins to fall,
its potential energy is
changed into kinetic energy.
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11. Energy Changes Form
A car engine burns gasoline,
converting the chemical energy
in gasoline into mechanical
energy. Solar cells change
radiant energy into electrical
energy. Energy changes form,
but the total amount of energy in
the universe stays the same.
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12. Energy Changes Form
Hybrid cars that use an
electric motor and a
gasoline engine for
power are now available.
Hybrid cars make
energy transformations
more efficient so the car
can travel farther on a
gallon of gas.
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13. Energy Changes Form
You wake up. It's a cool, sunny day, You
think you'll go for a bike ride. But first you
eat a good healthy breakfast. You are
taking the chemical energy stored in food
into your own body. Any time energy is
stored, it's called potential energy. It's
available for later use. Without your
needing to think about it, the cells in your
body will break down the chemical bonds
in the food and release the energy in
those bonds. You'll use the energy to stay
warm, to grow, to keep your internal
organs working, and to move your
muscles.
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14. Energy Changes Form
And you are moving. You jump up
from the table, grab a jacket, head
out the door. You hop on your
bicycle.
The energy of motion is called
kinetic energy. As you pump your
legs, the bicycle starts to roll. Your
kinetic energy is being transferred
to the bicycle.
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15. Energy Changes Form
Back at home, you turn on a radio It runs on electrical energy which travels along the
wires that connect a power plant to your home. The electrical energy used by the radio
is converted into sound energy.
Sound is another form of kinetic energy--it's air in motion. You can move your muscles
to make sound too. For example, you can hit a drum, sing or shout, or strum on a
guitar. The guitar strings, vocal cords, or drumhead, once set in motion, make the air
around them move.
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16. BIOMASS -- ENERGY FROM PLANT AND ANIMAL MATTER
Biomass is organic material made from plants and animals. Biomass contains stored
energy from the sun. Plants absorb the sun's energy in a process called
photosynthesis. The chemical energy in plants gets passed on to animals and people
that eat them. Biomass is a renewable energy source because we can always grow
more trees and crops, and waste will always exist. Some examples of biomass fuels
are wood, crops, manure, and some garbage.
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17. Transforming Chemical Energy
The matter contained in living organisms contains
chemical energy. When organisms die, chemical
compounds in their biomass break down.
Bacteria, fungi, and other organisms help convert
these chemical compounds to simpler chemicals
that can be used by other living things.
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18. Transforming Chemical Energy
Thermal energy also is released
as these changes occur.
Example: A compose pile can
contain plant matter, such as grass
clippings and leaves. As the compost
pile decomposes, chemical energy is
converted into thermal energy. This
can cause the temperature of a
compost pile to reach 60° C.
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19. Transforming Electrical Energy
Every day you use electrical
energy. When you flip a
switch, or turn on a radio or
television, or use a hair
drier, you are transforming
electrical energy to other
forms of energy.
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20. Transforming Thermal Energy
 Chemical energy changes into thermal energy
when something burns.
 Electrical energy changes into thermal energy
when a wire that is carrying an electric current gets
hot.
 Thermal energy can be transformed into radiant
energy such as when a bar of metal is heated to a
high temperature, it glows and gives off light.
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21. Generating Electrical Energy
Every Power plant works on the same principle---energy is used to
turn a large generator. A generator is a devise that transforms kinetic
energy into electrical energy. In fossil fuel power plants, coal, oil, or
natural gas is burned to boil water. As the hot water boils, the steam
rushes through a turbine, which contains a set of narrowly spaced fan
blades. The steam pushes on the blades and turns the turbine, which
in turn rotates a shaft in the generator to produce the electrical energy.
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22. Power Plants
Almost 90 percent of the electrical energy generated in the
U.S. is produced by nuclear and fossil fuel power plants.
Other types of power plants include Hydroelectric and wind.
Hydroelectric power plants transform the kinetic energy of
moving water into electrical energy. Wind power plants
transform the kinetic energy of moving air into electrical
energy.
Sources of Electrical Energy in the U.S.
20%
Coal
Oil
3% Gas
51%
9% Hydro
Other Renewable
14% Nuclear
3%
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23. Quick Review of Energy
 Changing Forms
Heat usually is one of the forms of energy produced in energy
transformations.
The law of conservation of energy states that energy cannot
be created or destroyed; it can only change form.
The total energy doesn’t change when an energy
transformation occurs.
As an object rises and falls, kinetic and potential energy are
transformed into each other, but the total energy doesn’t
change.
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24. Generating Electrical Energy
 A generator converts kinetic energy into electrical
energy.
 Burning fossil fuels produces thermal energy that is
used to boil water and produce steam.
 In a power plant, steam is used to spin a turbine
which then spins an electric generator.
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