1 Chapter 2Energy and Matter 2.1 Energy Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Energy makes objects move. makes things stop. is needed to “do work”. Energy

3 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

4 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

5 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

6 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

7 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)

8 Heat is measured in joules or calories Joules (J) = 1 calorie (cal) (exact) 1 kJ = 1000 J 1 kilocalorie (kcal) = 1000 calories (cal) Units for Measuring Energy or Heat

9 Examples of Energy In Joules

10 Learning Check How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized?

11 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 = J Set Up:150 J x 1 cal = 36 cal J