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Unformatted text preview: Lecture 20- Energy and Thermodynamics Systems- Closed System- Only energy can be exchanged between system and surroundings- Example: planet Earth- Open System - Both energy and matter can be exchanged between system and surroundings- Example: ocean- Isolated System- Neither matter or energy can be exchanged between system and surroundings- Example: a perfect thermos Types of Energy- Kinetic- Potential- Chemical-Potential (i.e. sugars, fats, proteins; through chemical bonds) 1 st Law of Thermodynamics- The total energy of the universe is constant; can’t be created or destroyed, but can be converted 2 nd Law of Thermodynamics- Every energy transfer or transformation increases the disorder (entropy) of the universe- The entropy of an isolated system always increases Entropy and Efficiency- Energy transfers are never 100% efficient- Lose a lot of energy as heat, the ultimate form of disorder, randomness (high entropy) - 40% of the kinetic energy in our food goes to contraction of muscles (waste)...
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- Spring '09