Chapter 2 Energy and Matter

2.1 Energy

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Energy

Energy

• makes objects move.

• makes things stop.

• is needed to “do work.”

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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.

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Potential Energy

Potential energy is• stored energy.

Examples are

• water behind a dam.

• a compressed spring.

• chemical bonds in gasoline, coal, or food.

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Kinetic Energy

Kinetic energy is the

• energy of motion.

Examples are

• swimming.

• water flowing over a dam.

• working out.

• burning gasoline.

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ExamplesIdentify the energy as potential or kinetic.

A. RollerbladingB. a peanut butter and jelly sandwichC. mowing the lawnD. gasoline in the gas tank

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Units for Measuring Energy or HeatHeat is measured in joules or calories.

4.184 Joules (J) = 1 calorie (cal)

1 kJ = 1000 J

1 kilocalorie (kcal) = 1000 calories (cal)

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Examples of Energy In Joules

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ExamplesHow many cal are obtained from a pat of butterif it provides 150 J of energy when metabolized?

1) 0.36 cal

2) 36 cal

3) 630 cal

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Chapter 2 Energy and Matter

2.2 Energy and

Nutrition

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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.

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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 = 4.184 kJ

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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

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Energy Values for Some Foods

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Energy Requirements

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

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ExamplesA 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)

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Chapter 2 Energy and Matter2.3

Temperature Conversions

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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.

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Temperature Scales

Temperature Scales

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• are Fahrenheit, Celsius, and Kelvin.

• have reference points for the boiling and freezing points of water.

ExamplesA. 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) 100 2) 180 3) 273

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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.

TF = 9/5 TC + 32

orTF = 1.8 TC + 32

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Celsius Formula

• TC is obtained by rearranging the equation for TF.

TF = 1.8TC + 32 °

• Subtract 32 ° from both sides.

TF - 32 ° = 1.8 TC ( + 32 ° – 32 °)

TF - 32 ° = 1.8 TC

• Divide by 1.8 = °F - 32 ° = 1.8 TC

1.8 1.8

TF - 32 ° = TC

1.8

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Solving A Temperature Problem

A person with hypothermia has abody temperature of 34.8 °C. What is that temperature in °F?

TF = 1.8 TC + 32

TF = 1.8 (34.8 °C) + 32 ° exact 3 SFs exact

= 62.6 + 32 ° (addition)

= 94.6 °F tenth’s

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Kelvin Temperature ScaleThe Kelvin temperature scale• has 100 units between the freezing and boiling

points of water. 100 K = 100 °C or 1 K = 1 °C

• is obtained by adding 273 to the Celsius temperature.

TK = TC + 273

• contains the lowest possible temperature, absolute zero (0 K).

0 K = –273 °C

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Learning Check The normal body temperature of a

chickadee is 105.8 °F. What is that temperature on the Celsius scale?

1) 73.8 °C 2) 58.8 °C3) 41.0 °C

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ExamplesA pepperoni pizza is baked at 455 °F. What temperature is needed on the Celsius scale?

1) 423 °C2) 235 °C3) 221 °C

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Temperatures

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ExamplesWhat is normal body temperature of 37 °C in kelvins?

1) 236 K2) 310 K 3) 342 K

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