Energy Transformations
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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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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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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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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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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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Tracking Energy Transformations
•Because of friction,
the mechanical
parts of the bicycle
are warmer, too.
The energy transformations
that occur when people
•Thermal
energy
is
exercise, when cars run, when
almost
living things grow and
even always
produced
by an
when stars explode,
all
produce thermal energy.
energy
transformation.
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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
Sources of Electrical Energy in the U.S.
energy.
20%
Coal
Oil
3%
Gas
51%
9%
Hydro
Other Renewable
14%
Nuclear
3%
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Quick Review
• Changing Forms of Energy
– 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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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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