P1.1 - Energy Transfer by Heating

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  • P1.1 - Energy Transfer by Heating
    • 1.1
      • Infrared radiation is energy transfer by electromagne-tic waves.
      • All objects emit infrared radiation.
      • The hotter the object, the more infrared radiation it emits in a given time.
    • 1.2
      • Dark, matte surfaces emit radiation the quickest.
      • Dark, matte surfaces absorb radiation the quickest.
      • Light, shiny surfaces reflect the most infrared radiation.
    • 1.3
      • Particles in a solid are held next to each other, vibrating in their fixes positions.
      • Particles in a liquid move about at random  and are in contact with each other.
      • Particles in a gas more about randomly and are farther apart than particles in other matters.
      • Flow, shape, volume and density are properties used to describe each state of matter.
    • 1.4
      • Metals are the best conductors.
      • Wool and fibreglass are good insulators.
      • Conduction in a metal is mainly due to free electrons transferring energy inside the metal.
      • Non-metals are poor conductors as they don't have free electrons.
    • 1.5
      • Convection takes place in a fluid.
      • Convection is the circulation of a fluid caused by heating it.
      • Heating a fluid makes it less dense so it rises and causes circulation.
    • 1.7
      • The rate at which energy is transferred depends on:
        • Material the object is in contact with.
          • Objects shape.
            • Objects surface area.
      • To maximise the rate of energy transfer to keep things cool:
        • Make sure they're conductors.
          • Paint them dull and black
            • Have the air flow around them maximised.
      • To minimise the rate of energy transfer to keep things warm:
        • Make sure they're insulators.
          • Make them white and shiny.
            • Prevent convection currents by trapping air in small pockets.
    • 1.6
      • Evaporation is when a liquid turns into a gas.
        • The rate of evaporation is increased by:
          • Increasing the surface area.
            • Increasing the temperature.
              • Creating a draught of air across the liquid's surface.
      • Condensation is when a gas turns into a liquid.
        • The rate of condensation is increased by:
          • Increasing the surface area.
            • Reducing the surface temperature.
    • 1.8
      • The greater the mass, the more slowly its temperature increases when heated.
      • Specific heat capacity:       E = m x c x ?
        • E = energy transferred, J
        • M = mass, kg
        • c = specific heat capacity, J/kg°C
        • ? = temperature change, °C
      • The rate of temperature change in a substance when heated depends on the energy transferred to it, its heat and its SHC.
    • 1.9
      • The rate of energy transfer to and from our homes can be reduced.
        • Install insulators to reduce it.
      • U-values tell us how much energy per second passes through different materials.
        • The lower the U-value, the better the material is as an insulator.
      • To minimise the rate of energy transfer out of houses you can:
        • Fit double glazing.
        • Fit fibreglass loft insulation.
        • Fit cavity wall insulation.
        • Fit draught proofing.

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