P1.1 Energy

P1.1 Energy

Infrared Radiation
1. All objects emit and absorb infrared radiation
  1. The hotter an object the more infrared radiation it radiates
  2. Dark, matt surfaces
    1. Good absorbers
    2. Good emitters
  3. Light, shiny surfaces
    1. Poor absorbers
    2. Poor emitters
    3. Good reflectors
Kinetic Theory
1. Solids
  1. Strong forces of attraction
  2. Particles have little energy
  3. Particles vibrate around fixed positions
    1. Regular and fixed arrangement
2. Liquids
  1. Weaker forces of attraction
  2. Irregular arrangement
  3. More energy than solids
  4. Move in random directions at slower speeds
3. Gases
  1. No attraction
  2. No arrangement
  3. Random directions at high speeds
  4. Lots of energy
Energy Transfer by heating
1. Energy transfers
  1. Conduction
    1. Vibrating particles pass on kinetic energy
      1. Faster in solids
        Particles closer; collide more often
      2. Metals good conductors
        Free electrons collide with particles
  2. Convection
    1. Area gets hot
      1. Particles move further apart
        Area less dense
        Lighter
        So it rises
        Starts to cool
        Falls back down
  3. Evaporation
    1. Liquid turns into gas
      1. Particles with most energy overcome forces of attraction and escape
      2. Affects rate
        Temperature
        Faster if higher
        Density
        Faster if lower
        Surface area
        Faster if larger
        Airflow
        Faster if greater
  4. Condensation
    1. Gas turns into liquid
      1. Particles lose kinetic energy
      2. Affects rate
        Temperature
        Faster if lower
        Temperature of surface
        Faster if lower
        Density
        Faster if higher
        Airflow
        Faster if less
2. Rate at which an object transfers energy by heating depends on
  1. Surface area and volume
  2. Nature of the surface
  3. Material
3. The bigger the temperature difference between an object and its surroundings
  1. The faster the rate at which energy is transferred by heating
Heating and insulating buildings
1. U- Value
  1. How effective an insulator it is
    1. The lower the better
2. Specific heat capacity
  1. Amount of energy required to change the temperature of one kilogram of the substance by one degree celsius
    1. E = m x c x 0 (theta)
3. Solar panels
  1. Contain water which is heated by sun, water then used to heat buildings or provide hot water

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