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1032 Chapter 2
 

1032 Chapter 2

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    1032 Chapter 2 1032 Chapter 2 Presentation 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.
      • your heart pumps blood.
      • water goes over a dam.
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
    • 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.
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
    • Kinetic Energy
      • Kinetic energy is the
      • energy of matter in motion.
      • Examples are
      • swimming.
      • water flowing over a dam.
      • working out.
      • burning gasoline.
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
    • Learning Check
      • Identify the energy as potential or kinetic.
      • A. roller blading
      • 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.
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
    • Temperature Scales
      • Temperature Scales
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
      • 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?
      Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
      • 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