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Lesson 2 Summary
Use with pp. 362–365
Lesson 2: How does energy change form?
Changing Forms of Energy
Ways That Energy Travels
Energy can change from one form into
another. For example, living things store
potential energy as chemical energy.
Chemical energy in your body changes to
mechanical energy and heat energy as you
move. Potential energy can also change
into the forms listed below:
• Chemical energy This energy holds
particles of matter together. Food and
fuel contain chemical energy.
• Mechanical energy This is the energy
of moving objects. Moving parts in
machines use kinetic energy. Your body
also uses mechanical energy when it
moves.
• Electrical energy This energy can
pass through wires made of special
metal. We use this energy to power
many machines.
• Light energy We see the Sun’s energy
as light. Plants use light energy to make
food.
• Thermal energy This form of energy
makes particles move faster. We feel
thermal energy as heat.
Energy can travel from one place to
another. A moving object carries energy.
For example, you can feel the energy a
moving ball is carrying when you catch it.
Energy can also travel as waves. Look at
the rope on page 365 in your textbook. A
person is moving the rope from side to side.
This makes energy move along the rope
in waves. Light energy and kinetic energy
move in waves.
Energy in water moves in waves. These
waves can be small. Waves caused by
hurricanes can be huge. The size of a wave
depends on how much energy it carries.
Waves lose strength as they move away
from their source.
When you turn on a light, this helps
change electrical energy to light energy.
The light bulb will get hot. This is because
some of the electrical energy changes
to heat energy. Energy cannot change
completely from one form to another. Some
energy is given off as heat.
People also use machines to change
forms of energy. An electric toothbrush
can change chemical energy into electrical
energy. It changes electrical energy to
mechanical energy when the toothbrush is
turned on.
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Chapter 13, Lesson 2 Summary
You can measure the amount of energy
that a wave carries. One way you can do
this is by measuring the width of a wave.
The width is the distance between the
bottom of the wave to the top of the wave.
The bottom of a wave is called a trough.
The top of a wave is called a crest. Wide
waves have lots of energy. Thin waves have
less energy.
You can also measure the length of an
energy wave. The length of a wave is the
distance from the top of one crest to the top
of the next crest. Shorter waves have lots of
energy. Longer waves have less energy.
© Pearson Education, Inc. 3
Using Energy
Parts of a Wave
Quick Study
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Lesson 2 Checkpoint
Use with pp. 362–365
Lesson 2 Checkpoint
1. What form of energy do living things change into mechanical
energy and thermal energy?
2. Name two types of energy that travel in waves.
3. What happens to energy as it travels away from the source?
Main Idea and Details Read the first paragraph under “Parts
of a Wave.” Use a graphic organizer. What is the main idea? What
are the supporting details?
© Pearson Education, Inc. 3
4.
Quick Study
Chapter 13, Lesson 2 Checkpoint
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