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# 1032 Chapter 2

## on Jun 26, 2008

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## 1032 Chapter 2Presentation Transcript

• Chapter 2 Energy and Matter Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
• Energy
• makes objects move.
• makes things stop.
• is needed to “do work”.
Energy
• Work
• Work is done when
• you climb.
• you lift a bag of groceries.
• you ride a bicycle.
• you breathe.
• water goes over a dam.
• Potential Energy
• Potential energy is
• energy stored for use at
• a later time.
• Examples are
• water behind a dam.
• a compressed spring.
• chemical bonds in gasoline, coal, or food.
• Kinetic Energy
• Kinetic energy is the
• energy of matter in motion.
• Examples are
• swimming.
• water flowing over a dam.
• working out.
• burning gasoline.
• Learning Check
• Identify the energy as potential or kinetic.
• B. a peanut butter and jelly sandwich
• C. mowing the lawn
• D. gasoline in the gas tank
• Heat is measured in joules or calories.
• 4.184 Joules (J) = 1 calorie (cal) (exact)
• 1 kJ = 1000 J
• 1 kilocalorie (kcal) = 1000 calories (cal)
Units for Measuring Energy or Heat
• Examples of Energy In Joules
• Learning Check
• How many calories are obtained from a pat of butter
• if it provides 150 J of energy when metabolized?
• 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.
• 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
• 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
• Energy Values for Some Foods TABLE 2.2
• Energy Requirements
• The amount of energy needed each day depends on age, sex, and physical activity .
TABLE 2.3
• A cup of whole milk contains 12 g of carbohydrate, 9.0 g of fat, and 5.0 g of protein. How many kcal (Cal) does a cup of milk contain?
• 1) 48 kcal (or Cal)
• 2) 81 kcal (or Cal)
• 3) 150 kcal (or Cal)
Learning Check
• Temperature
• 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.
• Temperature Scales
• Temperature Scales
• are Fahrenheit, Celsius, and Kelvin.
• have reference points for the boiling and freezing points of water.
• 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) 100 2) 180 3) 273
Learning Check
• Celsius Formula
• Solving A Temperature Problem
• A person with hypothermia has a
• body temperature of 94.6°F. What is that temperature in °C?
• 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
Learning Check
• The Kelvin temperature scale
• is obtained by adding 273 to the Celsius temperature.
• T K = T C + 273
• contains the lowest possible temperature, absolute zero (0 K).
• 0 K = –273 °C
Kelvin Temperature Scale
• Temperatures TABLE 2.5
• What is normal body temperature of 37°C in Kelvins?
• 1) 236 K
• 2) 310. K
• 3) 342 K
Learning Check
• Specific heat
• is different for different substances.
• is the amount of heat that raises the temperature of 1 g of a substance by 1°C.
• in the SI system has units of J/g  C.
• in the metric system has units of cal/g  C.
Specific Heat
• Examples of Specific Heats TABLE 2.6 cal/g°C 0.214 0.0920 0.0308 0.108 0.0562 0.125 0.488 0.588 0.207 0.100
• Heat Equation
• q = m x C x  T
• m: mass of substance
• C: specific heat of the substance
•  T: temperature change
• Learning Check
• What is the specific heat of a metal if 24.8 g absorbs
• 275 J of energy and the temperature rises from 20.2  C to
• 24.5  C?
• How many kilojoules are needed to raise the temperature of 325 g of water from 15.0°C to 77.0°C?
• 1) 20.4 kJ
• 2) 77.7 kJ
• 3) 84.3 kJ
Learning Check