CHAPTER 9: HEAT

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CHAPTER 9 HEAT

• Section 9.1
• Temperature Thermal Equilibrium

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Temperature Thermal Equilibrium

• Kinetic Molecular Theory
• Particles are always in motion
• In hot objects, the particles move faster and
  therefore have a higher kinetic energy.
• Thermal energy results from this motion.
• We can measure temperature because of thermal
  equilibrium.

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Temperature

• Temperature measures hotness of an object,
  not the heat (thats measured in calories or
  joules).
• Particles at a higher temperature move faster and
  have a larger kinetic energy.
• Kelvin is the absolute temperature scale its
  where zero really does mean 0!
• K 273 0C

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CHAPTER 9 HEAT

• Section 9.2
• Defining Heat

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What is Heat?

• Heat is NOT the same as temperature!
• Heat is the energy transferred between objects.
• It is measured in a variety of units (see pg.
  307)
• Joules (J) this is the SI unit of energy
• calorie (cal) this is an old measurement. 1
  cal 4.184 J

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What is Heat?

• Calorie (with a capital C) this is used in
  nutrition. 1 Cal 1000 cal or 4184 J
• British Thermal Unit (Btu) English unit of
  measure used in air conditioning and
  refrigeration. 1 Btu 1055 J.
• therm used in measuring natural gas. 1 therm
  100,000 Btu 105,500,000 J.

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Energy Transfer

• Thermal energy (heat) is transferred in 3 ways
• Conduction transfer of kinetic energy when
  particles collide (its what happens in
  thermometers).
• Convection movement of fluids because of their
  different densities at different temperatures
  (its what causes our weather.
• Radiation transfer of radiation by
  electromagnetic waves. Does not need matter to
  happen. Solar energy is transferred this way.

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Heat Work

• We learned in Chapter 5 that the change in work
  the change in kinetic energy.
• According to the Law of Conservation of Energy,
  the total amount of energy (potential, kinetic,
  etc) is a system is never created or destroyed.
• Formula
• ?PE ?KE ?U 0
• where ?U change in internal energy or heat