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8th Grade Chapter 5 Lesson 2
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8th Grade Chapter 5 Lesson 2

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8th Grade Chapter 5 Lesson 2 8th Grade Chapter 5 Lesson 2 Presentation Transcript

  • Pgs. 186- 199 For Student Use Only 8 th Grade Chapter 5 Lesson 2
  • Heat Transfer
    • Remember: Charles said that gases expand dramatically when heated
    • Liquids and Solids expand when heated also
      • Have you ever experiences expansion in the real world?
    • Example:
    • Expansion joints in bridges
    • Gas Expansion
      • Gases expand because of loose cohesive bonds
    • Liquid Expansion:
      • Liquids expand also more than solids from lack of cohesive bonds
    • Solid Expansion
      • Solids expand differently due to stronger cohesion of molecules
    Heat Transfer
  • Heat Transfer
    • Expansion Joints
        • This allows bridge to expand and contract with temperatures
        • Concrete and Steel expand at nearly the same rate
    • Expansion of Water:
      • Water molecules draw closer together as temperature drops
      • 4 ° C is maximum density of water
      • O °C water begins to get larger and it freezes
    • Water forms crystals that make the it larger and less dense (this is why ice floats).
  • Heat Transfer
    • Thermostat
      • Automatically regulates temperature
      • Uses Bimetallic strip to sense temperature changes
        • Metals expand at different rates
      • Cornelius Drebbel constructed the first thermostat
  • Heat Transfer
    • Heat flows from the hotter object to the colder object
    • Cold is merely a state of lower thermal energy
    • Heat flows in three different ways:
      • Conduction
      • Convection
      • Radiation
  • Heat Transfer
    • Conduction:
    • Heat is transferred from one object to another
    • Think direct contact
    • Some materials are good conductors or some are not good conductors
    • Miner’s safety lamp disipates heat by conduction and keeps open flames from igniting methane gas
  • Heat Transfer
    • Convection:
    • Heat is transferred through a fluid
    • Warmer fluids rise and colder fluids sink
    • This is known as convection currents
    • Convection currents are found in winds and waves and ovens
  • Heat Transfer
    • Radiation:
    • Heat is transferred through space in the electromagnetic waves
    • This is a slower process and the glass stays close to the same temperature
    • Greenhouse Effect:
    • The atmosphere lets radiation in but traps heat
  • Heat Transfer
    • Radiant Heat:
    • Radiation is absorbed and transferred much more readily from dark objects
    • Vacuum flask stores liquid oxygen, hydrogen, or other liquid gases.
    • Vacuum limits space conduction
    • Thermoses are a type of vacuum chamber
  • Heat Transfer
    • Heat Transfer
      • Heating homes uses a lot of different methods
      • Radiators- radiate heat
      • Conduction- is used to transfer the heat from the water to the metal bars
      • Convection – uses forced-air uses convection currents to help circulate the air.