chapter 2energy and matter 2.1 energy 1. makes objects move. makes things stop. is needed to “do...
TRANSCRIPT
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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