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1 Chapter 2Energy and Matter 2.1 Energy Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Slide 2 2 Learning Goals Identify energy as potential or kinetic. Use caloric values to calculate the kilocalories (Cal) in a food. Given a temperature, calculate a corresponding temperature on another scale. Use specific heat to calculate heat loss or gain, temperature change, or mass of a sample. Identify the physical state of a substance as a solid, liquid, or gas. Describe the changes of state between solids, liquids, and gases; calculate the energy involved. Slide 3 3 Energy makes objects move. makes things stop. is needed to do work. Energy Slide 4 4 Work Work is done when you climb. you lift a bag of groceries. you ride a bicycle. you breathe. your heart pumps blood. water goes over a dam. Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Slide 5 5 Potential Energy Potential energy is energy stored for use at a later time. Examples are water behind a dam. a compressed spring. chemical bonds in gasoline, coal, or food. Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Slide 6 6 Kinetic Energy Kinetic energy is the energy of matter in motion. Examples are swimming. water flowing over a dam. working out. burning gasoline. Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Slide 7 7 Learning Check Identify the energy as potential or kinetic. A. roller blading B. a peanut butter and jelly sandwich C. mowing the lawn D. gasoline in the gas tank Slide 8 8 Solution Identify the energy as 1) potential or 2) kinetic. A. roller blading (kinetic) B. a peanut butter and jelly sandwich (potential) C. mowing the lawn (kinetic) D. gasoline in the gas tank (potential) Slide 9 9 Heat is measured in joules or calories. 4.184 Joules (J) = 1 calorie (cal) (exact) 1 kJ = 1000 J 1 kilocalorie (kcal) = 1000 calories (cal) Units for Measuring Energy or Heat Slide 10 10 Examples of Energy In Joules Slide 11 11 Learning Check How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? Slide 12 12 Solution How many calories are obtained is a pat of butter if it provides 150 J of energy when metabolized? Given: 150 J Need: calories Plan: J cal Equality: 1 cal = 4.184 J Set Up:150 J x 1 cal = 36 cal 4.184 J