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

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

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

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

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

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

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)

Units for Measuring Energy or Heat 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)

Examples of Energy In Joules

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

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