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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? _______________________________________________________________ 2. When hand warmers are activated, do they create energy? Explain your answer. _______________________________________________________________ 3. Why is chemical energy a form of potential energy? _______________________________________________________________ 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