1. Chapter 2 Energy and Matter
2.1
Energy
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Publishing as Benjamin Cummings

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

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 © 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 © 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 © 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. 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)

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: J
Need: calories
Plan: J  cal
Equality: cal = J
Set Up: 150 J x 1 cal = 36 cal
4.184 J