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

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For Student Use Only

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    • 1. Pgs. 186- 199 For Student Use Only 8 th Grade Chapter 5 Lesson 2
    • 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
    • 3.
      • 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
    • 4. 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).
    • 5. Heat Transfer
      • Thermostat
        • Automatically regulates temperature
        • Uses Bimetallic strip to sense temperature changes
          • Metals expand at different rates
        • Cornelius Drebbel constructed the first thermostat
    • 6. 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
    • 7. 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
    • 8. 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
    • 9. 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
    • 10. 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
    • 11. 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.