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

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.

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.

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

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

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

Energy Comparison

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)

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 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

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 = 4.184 J

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.