P1.1

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  • P1.1 energy transfer by heating
    • Infrared radiation
      • energy transfer by electromagnetic waves
      • all objects emit this
      • the hotter the object, the more radiation it emits
    • surfaces and radiation
      • dark matt surfaces
        • emit more radiation
        • absorb more radiation
      • light shiny surfaces
        • reflect more infrared radiation
    • states of matter
      • solid
        • fixed shape and volume
        • particles held in fixed positions
      • liquid
        • fixed volume
        • no shape
        • particles move randomly touching each other
      • gas
        • no fixed shape or volume
        • particles move randomly and are apart
    • conduction
      • metals=best conductors
        • free electrons
      • wool/ fibreglass = best insulators
        • no free electrons
    • convection
      • circulation of a fluid by heating it
      • only in liquids or gases
      • less dense = rises upwards
    • evaporation
      • when a liquid turns into a gas
      • cools-faster moving molecules escaping
      • increased as
        • higher surface area
        • increase in temp
        • a draught of air
    • condensation
      • when a gas turns into a liquid
      • increased by
        • increasing area of surface
        • reducing temp on the surface
    • transfer by design
      • vacuum flask
        • plastic cap
          • evaporation
        • vacuum between two walls
          • conduction/ convection
        • plastic cover
          • good conductor
        • spondge pad
          • conduction
        • silvered sufaces
          • radiation
      • rate of transfer
        • contact of substance
        • objects shape
        • surface area
    • specific heat capacity
      • heat required to raise the temperature of the unit mass of a given substance by a given amount
      • higher mass = slower temp increase when heated
    • home insulation
      • Uvalue
        • how much energy per second passes through different materials
        • lower = more efficient
      • loft insulation
        • fibreglass-less conduction
      • cavity wall insulation
        • stops convection currents and radiation
      • double glazing
      • aluminium foil behind readiators
        • radiation
      • payback time
        • cost / savings per year

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