3 4 Energy makes objects move makes things

3. 4 Energy • makes objects move. • makes things stop. • is defined as the ability to do work. A defibrillator provides electrical energy to heart muscle to reestablish normal rhythm. Learning Goal Identify energy as potential or kinetic; convert between units of energy. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Kinetic Energy Kinetic energy is the energy of motion. Examples are the following: • swimming • water flowing over a dam • working out The movement of water that flows from the top of a dam is an example of kinetic energy. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Potential Energy Potential energy is energy stored for use at a later time. Examples are the following: • water at the top of a dam • a compressed spring • chemical bonds in gasoline, coal, or food The water at the top of a dam has potential energy by virtue of its position. As the water falls over and down the dam, the potential energy is converted to kinetic energy. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check Identify the energy in each example as potential or kinetic: A. rollerblading B. a peanut butter and jelly sandwich C. mowing the lawn D. gasoline in the gas tank General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution Identify the energy in each example as potential or kinetic: A. rollerblading kinetic B. a peanut butter and jelly sandwich potential C. mowing the lawn kinetic D. gasoline in the gas tank potential General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Heat and Energy Heat is the energy associated with the movement of particles. The faster the particles move, the greater the heat or thermal energy of the substance. Given an ice cube, as heat is added, the H 2 O molecules • that are moving slowly increase their motion. • eventually have enough energy to change the ice cube from a solid to a liquid. Core Chemistry Skill Using Energy Units General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Units of Energy is measured in • the SI unit, the joule (J), or in kilojoules (k. J), 1000 joules. • units of calories (cal) or in kilocalories (kcal), 1000 calories. The calorie is defined as the amount of energy needed to raise the temperature of 1 g of water by 1 °C. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Energy Comparison General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? A. 0. 86 cal B. 630 cal C. 36 cal General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? STEP 1 State given and needed quantities. ANALYZE THE PROBLEM Given 150 J Need calories STEP 2 Write a plan to convert the given unit to the needed unit. Energy joules calories Factor General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? STEP 3 State the equalities and conversion factors. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution How many calories are obtained from a pat of butter if it provides 150 J of energy when metabolized? STEP 4 Set up the problem to calculate the needed quantity. × General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake Answer is C. © 2016 Pearson Education, Inc.