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Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
INTEGRATING CHEMISTRY
Cross-Disciplinary
Chemical Reactions
Read the following paragraphs, and complete the exercises below.
DIFFERENT FORMS OF ENERGY
Energy can be defined as the ability to move or change matter. Energy occurs in
different forms. An object has kinetic energy because of its motion. For example,
a boulder rolling down a hill has kinetic energy. Because the boulder is in motion,
it could move another boulder in a collision.
Another kind of energy is potential energy, the energy due to position. A
motionless boulder at the top of a hill has no kinetic energy because the boulder is
not moving. But the boulder has potential energy due to its position above the
ground at the bottom of the hill. In this example, the boulder has potential energy
because of its gravitational attraction to Earth.
POTENTIAL ENERGY CAN BE STORED IN CHEMICALS
An object’s location is not the only way it can acquire potential energy. Consider
hand warmers people use for cold weather activities. The hand warmers are small
plastic pouches containing water and solid sodium acetate. The sodium acetate
dissolves when the pouch is heated. Once the pouch cools, it can easily be carried
in a pocket.
When needed, a metal disc inside the warmer is snapped, and the warmer gives
off energy as heat for several minutes as the chemical crystallizes. When this
happens, the warmer releases energy as heat that was once stored when energy
was first added to the pouch as heat.
Rather than having potential energy because of the location, as the boulder had,
the hand warmers have stored energy because of the arrangement of the sodium
acetate atoms. Energy stored in this way is a form of potential energy called
chemical energy. Another substance with chemical energy is gasoline, which
releases energy as light and heat when it is ignited.
EXERCISES
1. What is energy?
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2. When hand warmers are activated, do they create energy? Explain your
answer.
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3. Why is chemical energy a form of potential energy?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science Spectrum
34
Work and Energy