1. Chapter 3 Matter and Energy
Learning Goal Identify energy as potential or kinetic; convert between
units of energy.
© 2014 Pearson Education, Inc.

2. is defined as the ability to do work
Energy
Energy
is defined as the ability to do work
can be classified as either kinetic or
potential energy
Kinetic energy is the energy of motion.
Potential energy is determined by the position of an object or its chemical composition.
© 2014 Pearson Education, Inc.

3. Potential or Kinetic Energy?
Water in a reservoir behind a dam has
potential energy.
When the water is released and flows over the dam, its potential energy is converted to kinetic energy.

4. Learning Check
Identify the energy in each example as
(1) potential or (2) kinetic.
A. rollerblading
B. a peanut butter and jelly sandwich
C. mowing the lawn
D. gasoline in the gas tank

5. Solution
Identify the energy in each example as
(1) potential or (2) kinetic.
A. rollerblading (2) kinetic
B. a peanut butter and jelly sandwich
(1) potential
C. mowing the lawn (2) kinetic
D. gasoline in the gas tank (1) potential

6. Heat and Units of Energy, Joules
Heat is associated with the motion of particles. The faster the particles move, the greater the thermal energy of the substance.
The SI unit of energy is the joule (J).
1 kJ = 1000 J

7. Energy Comparison

8. Heat and Units of Energy, Calories
The unit calorie is the amount of energy needed to raise the temperature of 1 g of water by 1 o C.
4.184 Joules (J) = 1 calorie (cal) (exact)
1 kilocalorie (kcal) = 1000 calories (cal)

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

10. Solution
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 1 Given 150 J Need calories
Step 2 Write a plan to convert units.
joules Energy calories
factor

11. Solution How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 3 State equalities, conversion factors.
1 cal = J

12. Solution How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Step 4 Set up problem and calculate.