P1 Physics- Energy Transfer by Heating Part 1

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  • Energy Transfer by Heating
    • Infrared Radiation
      • Part of the electro- magnetic spectrum
        • Involves waves instead of particles
      • We can detect infrared radiation with our skin- it makes us feel warm
      • All objects EMIT infrared radiation
        • The hotter it is, the more infrared radiation it emits in a given time
      • Infrared Radiation can travel through a vacuum
        • This is how we get energy from the sun
      • Surfaces and Radiation
        • black, matt surfaces
          • Good at absorbing Infrared Radiation
          • Good at emitting Infrared Radiation
        • light, shiny surfaces
          • Bad at emitting infrared radiation
          • Bad at absorbing infrared radiaition
          • Good Reflectors of Infrared Radiation
    • States of Matter
      • There are 3 states of matter, solid, liquid and gas
      • Solid
        • particles vibrate at fixed positions
        • Have a fixed shape
        • They cannot flow
        • They cannot be compressed or squashed
      • Liquid
        • Particles are in contact with each other
        • The particles can move about at random
      • Gas
        • Particles move about randomly
        • Particles are further apart than a liquid and solid
        • Gases can move quickly in any direction
      • Gas has the most energy and solid has the least energy
    • Conduction
      • Occurs mainly in solids
      • Most liquids and gases are poor conductors
      • Conduction in a metal is mainly due to free electrons transferring energy inside the metal
      • Non-metals are poor conductors because they don't contain free electrons
      • Materials such as wool and fibreglass are good insulators because they contain trapped air.
    • Convection
      • Occurs in fluids- liquids and gases
      • When a fluid is heated it expands
        • The fluid becomes less dense and rises
          • The warm fluid is replaced by cooler, denser fluid
            • The resulting convection current transfers energy throughout the fluid
    • Evaporation
      • When a fluid turns into a gas
      • The most energetic liquid molecules escape the surface and enter the air
        • Therefore the temperature decreases
      • Evaporation causes cooling
      • Rate of Evaporation
        • Increased by increasing the surface area of the liquid
        • Increased by increasing the temperature of the liquid
        • increased by creating a draught of air across the liquids surface
    • Condensation
      • When gas turns into a liquid
      • often takes place on cold surfaces such as windows and mirrors
      • Rate of Condensation is increased by...
        • inreasing the surface area
        • reducing the surface temperature


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