Energy Transfer by Heating

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  • Energy Transfer by Heating
    • Infrared Radiation "heat"
      • No particles!!!
      • All objects emit and absorb radiation
      • Can be detected with skin by not eyes
      • Matt black surfaces= best emitters and absorbers
      • Shiny white surfaces= poor emitters and absorbers. Good reflectors
    • Kinetic Theory
      • Solids; particles are very close together, they vibrate around each other
        • Fixed shape
        • Fixed volume
      • Liquids; particles close together but can move around
        • Fixed volume
        • Takes shape of container
      • Gases; particles are very far apart, they move quickly and randomly
        • Fills space avaliable
    • Conduction
      • Metals are very good conductors- atoms arranged neatly and delocalised electrons
      • Poor conductors= insulators
        • eg, wood, air, polystyrene and plastic
    • Convection- liquids and gases
      • When heated particles gain kinetic energy/ vibrate
        • Liquid then expands- becomes less dense
          • The liquid rises as it is lighter
            • Cools and condenses- becomes more dense
              • Liquid falls
    • Evapouration
      • Some particles with enough energy escape from the surface of the water. Remaining liquid is cooler
      • To increase rate of evap; increase surface area, increase water temperature, wind/ fan/ draft
    • Condensation
      • Particles lose heat/kinetic energy. they move slower and closer together. gas condenses to a liquid
      • To increase rate of condensation; increase surface area
    • U-Values- rate of heat transfer through a material
      • High U-value = lots of heat transfer- bad
      • Low U-value = little heat transfer- good
    • Specific Heat Capacity
      • Energy required to change the temperature of one kilogram of the substance by one degree Celsius
      • Formula given

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