P1 Revision

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Mind Map on P1 Revision, created by olivia.jermy on 12/14/2013.
olivia.jermy
Mind Map by olivia.jermy, updated more than 1 year ago
olivia.jermy
Created by olivia.jermy about 11 years ago
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P1 Revision
  1. Heating houses
    1. Eventually objects reach the temperature of their surroundings
      1. The unit of temperature is degrees Celsius
        1. Heat is a measurement of energy
          1. The unit of energy is joules
            1. Heat flows from a warmer to a colder body
              1. When energy flows away from a warm object it's temperature decreases
                1. Temperature is a measure of how hot something is
                  1. When a substance is heated; it's temperature increases and particles vibrate faster. The average kinetic energy increases. Temperature is a measure of the average kinetic energy of particles
                    1. Heat is a measure of the total internal energy of an object
                      1. Energy needed to change the temperature of a liquid depends on 3 things; it's mass, what the liquid is and the rise in temperature
                        1. Heat is needed to melt a solid at it's melting point. Heat is needed to boil a liquid at it's boiling point
                          1. Latent Heat- the heat needed to change a state without a change in temperature
                            1. When an object is heated and it's temperature rises, energy is transferred
                              1. Specific heat capacity (J/kg degrees Celsius) - the amount of energy needed to change the temperature of one kilogram by one degree celsius
                                1. energy transferred= mass x specific heat capacity x temp change
                                2. Specific Latent Heat (J/kg) - the amount of energy needed to change the state of one kilogram of a substance without a change in temperature
                                  1. energy transferred= mass x specific latent heat
                                  2. When a substance changes state from solid to liquid or liquid to gas, energy is needed to break the bonds that hold the molecules together. This is why there is no change in temperature
                                  3. Keeping homes warm
                                    1. INSULATION- Air is a good insulator. Because there is air trapped inside coats, it does not allow energy to transfer from a warmer body to cold surroundings
                                      1. CONDUCTION- Particles in a solid are close together so energy is easily transferred as the particles vibrate
                                        1. INFRA RED RADIATION- Reflected from a shiny reflector. Used for cooking or generating electricity. A device at the focus of the reflector converts heat energy into electricity. It's absorbed by dull or rough surfaces
                                          1. Electromagnetic wave. Energy transfer by infra red radiation does not need a material. Energy can be transferred through a vacuum as in space
                                          2. A solid is a good conductor of heat and a vacuum is the best insulator because there are no air particles
                                            1. CONDUCTION- Electrons in metals can leave their atoms and move about freely. The atoms become charged ions. These ions are close together and are continually vibrating. When heated kinetic energy of the vibrations increases
                                              1. CONVECTION- When a gas is heated it expands. The same mass of gas occupies a greater volume. As the volume increases, the density decreases
                                                1. density (g/cm3) = mass/volume
                                                  1. Air is a good convector. As air in the cavity is warmed it rises through the cavity. Colder air falls and a convection current is formed. The convection current transfers energy. The air trapped in the foam stops convection from taking place
                                                  2. Energy efficiency= useful energy output (x100)/ total energy input
                                                    1. The home is the energy source and the atmosphere is the sink
                                                      1. A sink is a large object that does not change it's temperature by a noticeable amount when it absorbs energy from the source
                                                      2. Payback time= cost of insulation/ annual saving
                                                        1. Energy from a coal fire warms the room by radiation. The hot air rises up the chimney by convection and energy is transferred through the surrounding bricks by conduction

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