Summary 7.2

• energy is ability to perform work
• energy- moved against an opposing force
• two basic forms are kinetic, potential energy
• anything moving, has kinetic energy
• cannot destroy or create energy, cna be converted
• potential energy, energy stored because of position or arrangement of object
• random molecular motion - thermal energy
• energy provided by food
• potential energy depends on arrangement of atoms
• organic molecule cell structure - rich in chemical energy
• rearrangement of atomes releases potential energy
• organic molecules in food = high in chemical energy
• complex molecules broken down into simpler ones
• cars only use up 25% of the energy from gasoline
• glucose + oxygen react = cellular respiration
• 40% into energy, 60% into heat
• retaining some heat that is lost, keeps constant temperature
• sitting in class, radiates heat as 100 watt lightbulb
• calorie = amount of energy required to raise the temp of 1 gram of water by 1 degrees
• food expressed in kilocalories

Concept Check

1. At the top of the staircase, you have potential energy. It is stored as you prepare to walk down the stairs. As you slowly walk down the staircase, the potential energy is converted into kinetic energy.

2. During exercise, your body breaks down complex molecules into simpler molecules. 40% is used to power your body while you exercise. The other 60% however, is lost through sweat and other cooling methods.

3. 10kcal of energy = 10,000 calories. 100g water = 100(1) gram of water. 10kcal would raise 10 degrees of 100g of water