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