Chapter 2Energy and Matter 2.1 Energy 1

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

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. 3

Potential Energy Potential energy is stored energy. Examples are water behind a dam. a compressed spring. chemical bonds in gasoline, coal, or food. 4

Kinetic Energy Kinetic energy is the energy of motion. Examples are swimming. water flowing over a dam. working out. burning gasoline. 5

Examples Identify the energy as potential or kinetic. A. Rollerblading B. a peanut butter and jelly sandwich C. mowing the lawn D. gasoline in the gas tank 6

Units for Measuring Energy or Heat Heat is measured in joules or calories Joules (J) = 1 calorie (cal) 1 kJ = 1000 J 1 kilocalorie (kcal) = 1000 calories (cal) 7

Examples of Energy In Joules 8

Examples How many cal are obtained from a pat of butter if it provides 150 J of energy when metabolized? 1)0.36 cal 2)36 cal 3)630 cal 9

Chapter 2Energy and Matter 2.2 Energy and Nutrition 10

Calorimeters A calorimeter is used to measure heat transfer. can be made with a coffee cup and a thermometer. indicates the heat lost by a sample indicates the heat gained by water. 11

Energy and Nutrition On food labels, energy is shown as the nutritional Calorie, written with a capital C. In countries other than the U.S., energy is shown in kilojoules (kJ). 1 Cal = 1000 calories 1 Cal = 1 kcal 1 Cal = 1000 cal 1 Cal = 4184 J 1 Cal = kJ 12

Caloric Food Values The caloric or energy values for foods indicate the number of kcal (Cal) provided by 1 g of each type of food. Carbohydrate: 4 kcal 1 g Fat (lipid): 9 kcal 1 g Protein: 4 kcal 1 g 13

Energy Values for Some Foods 14

Energy Requirements The amount of energy needed each day depends on age, sex, and physical activity. 15

Examples A cup of whole milk contains 12 g of carbohydrate, 9 g of fat, and 5 g of protein. How many kcal (Cal) does a cup of milk contain (round answer to the tens place)? 1) 50 kcal (or Cal) 2) 80 kcal (or Cal) 3) 150 kcal (or Cal) 16

Chapter 2 Energy and Matter 2.3 Temperature Conversions 17

Temperature is a measure of how hot or cold an object is compared to another object. indicates that heat flows from the object with a higher temperature to the object with a lower temperature. is measured using a thermometer. 18

Temperature Scales 19 are Fahrenheit, Celsius, and Kelvin. have reference points for the boiling and freezing points of water.

Examples A. What is the temperature of freezing water? 1) 0 °F 2) 0 °C 3) 0 K B. What is the temperature of boiling water? 1) 100 °F 2) 32 °F 3) 373 K C. How many Celsius units are between the boiling and freezing points of water? 1) 1002) 1803)

Fahrenheit Formula On the Fahrenheit scale, there are 180 °F between the freezing and boiling points; on the Celsius scale there are 100 °C. 180 °F = 9 °F =1.8 °F 100 °C 5 °C 1 °C In the formula for the Fahrenheit temperature, adding 32 ° adjusts the zero point of water from 0 °C to 32 °F. T F = 9/5 T C + 32  or T F = 1.8 T C + 32  21

Celsius Formula T C is obtained by rearranging the equation for T F. T F = 1.8T C + 32 ° Subtract 32 ° from both sides. T F - 32 ° = 1.8 T C ( + 32 ° – 32 °) T F - 32 ° = 1.8 T C Divide by 1.8 =°F - 32 ° = 1.8 T C T F - 32 ° = T C

Solving A Temperature Problem A person with hypothermia has a body temperature of 34.8 °C. What is that temperature in °F? T F = 1.8 T C + 32  T F = 1.8 (34.8 °C) + 32 ° exact 3 SFs exact = ° (addition) = 94.6 °F tenth’s 23

Kelvin Temperature Scale The Kelvin temperature scale has 100 units between the freezing and boiling points of water. 100 K = 100 °Cor 1 K = 1 °C is obtained by adding 273 to the Celsius temperature. T K = T C contains the lowest possible temperature, absolute zero (0 K). 0 K = –273 °C 24

Learning Check The normal body temperature of a chickadee is °F. What is that temperature on the Celsius scale? 1) 73.8 °C 2) 58.8 °C 3) 41.0 °C 25

Examples A pepperoni pizza is baked at 455 °F. What temperature is needed on the Celsius scale? 1) 423 °C 2) 235 °C 3) 221 °C 26

Temperatures 27

Examples What is normal body temperature of 37 °C in kelvins? 1) 236 K 2) 310 K 3)342 K 28