Life’s MainspringAn Introduction to Energy Energy Is Central to Life•Universal relationship between energy and work, analogy of music box—requires winding, energy to run; so does life. Same laws of energy apply to music box and to living things to answer the following. –Energy source for life is the Sun, transferred by plants to us as food. How can one form of energy be converted and used for so many different activities? (How can winding music box be transferred to music?). –Energy tends to run out, downhill. (Why does music box wind down?). What Is Energy?•Definition of energy—capacity to do work (movement against an opposing force). Energy is a tricky subject because it can be measured but not seen. •Two main forms. –Potential energy: stored (chemical) energy like a rock on a hill or a lump of coal. –Kinetic energy: energy in motion like a rolling rock or heat from a burning lump of coal. Thermodynamics: The Study of Energy •First law of thermodynamics: energy is neither lost nor gained, but only transformed. –Examples: solar energy (kinetic) used to create carbohydrates (potential) in plants, and steam engine burning coal (potential) to generate heat to move pistons (kinetic). –Transfer of energy is never complete; some energy is always “lost”as heat. •What does heat have to do with random movement of molecules?
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