P1.1.3 Energy transfer by heating

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GCSE Physics (P1.1 Infrared Radiation) Mind Map on P1.1.3 Energy transfer by heating, created by fampulli on 05/30/2014.
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P1.1.3 Energy transfer by heating
  1. The transfer of energy by conduction, convection, evaporation and condensation involves particles
    1. Conduction
      1. Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles
        1. The process continues throughout the solid, gradually the kinetic energy is passed throughout the solid- causing a rise in temperature (at the other end of the solid)
          1. Hence an increase in heat radiating from the surface of the solid
        2. Conduction is usually faster in denser solids, as particles are closer together
          1. collide more frequently, passing energy between them
            1. Materials that have larger spaces between their particles conduct energy much more slowly
              1. these materials are insulators
                1. or this reason, glass is a better insulator than wood
                  1. wool and fibreglass are the best insulators
          2. in metals
            1. Metals contain lots of free electrons
              1. which move about at random and hold the positive metal ions together (and also collide with them)
                1. 1) When a metal rod is heated at one end, the free electrons at that end gain kinetic energy and move faster
                  1. 2) These electrons diffuse and collide with other free electrons and ions in the cooler parts of the metal
                    1. 3) As a result they transfer kinetic energy to these electrons and ions
                      1. and energy is transferred from the hot end of the metal to the cooler end
                  2. non-metals are good insulators, as they do not have free electrons
            2. convection
              1. is the circulation of a fluid (liquid or gas) caused by heating it
                1. it takes place
                  1. only in fluids (liquids or gases)
                    1. due to circulation (convection) currents within the fluid
                    2. 1) Most fluids expand when heated
                      1. 2) This is because the particles move about more, taking up more space
                        1. 3) Therefore the density decreases because the same mass of fluid now occupies a bigger volume
                          1. This principle explains convection currents
                            1. 1) As a fluid is heated, its reduction in density means that it rises
                              1. 2) This hot fluid displaces cooler fluid, or cools itself, and therefore falls due to an increase in density
                                1. 3) This cooler fluid is then heated once more- and the convection current continues circulating heat energy via the fluid
                    3. Condensation
                      1. when a gas (vapour) turns into a liquid
                        1. 1) When a gas cools, its particles lose kinetic energy and slow down- while the attractive forces pull the particles closer together
                          1. 2) If the temperature gets cold enough and the particles get close enough together-condensation will take place
                            1. 3) And the gas becomes a liquid
                          2. examples
                            1. water vapour in the air condenses when it come into contact with cold surfaces e.g. drinks glasses
                              1. steam: (inivisible) water vapour condenses to form tiny water droplets- as they spread out into cooler air
                              2. the factors which affect it
                                1. the rate of condensation will be faster if
                                  1. The temperature of the gas is lower
                                    1. This would mean the average particle energy is lower- so more particles will slow down enough to join together and form liquid droplets
                                    2. the temperature of the surface the gas touches is lower
                                      1. Density is higher
                                        1. fewer particles will have enough energy to overcome the stronger forces this density induces, meaning more will join together condense
                                        2. airflow is less
                                          1. the concentration of that particular fluid will be higher in a reduced airflow
                                            1. so the rate of condensation will be higher :3
                                  2. evaporation
                                    1. when a liquid turns into a gas
                                      1. Fun fact: particles can evaporate from a liquid at temps lower than that liquid's boiling point
                                        1. 1) Evaporation is when particles escape from a liquid
                                          1. if they are travelling in the right direction and have enough kinetic energy (k.e.), this will happen
                                            1. 2) Weak attractive forces exist between the molecules in the liquid
                                              1. 3) The faster molecules, which have more k.e., break away from the attraction of other molecules and escape from the liquid
                                                1. 4) After they leave, the liquid is cooler because the average k.e of the remaining molecules in the liquid has decreased
                                            2. uses of evap's cooling effect
                                              1. sweat: evaporates, cooling you down
                                                1. local anaesthetic: evaporates very easily, numbing your skin so that it becomes too cold to feel any pain
                                                2. the factors which affect it
                                                  1. the rate of evaporation will be faster if the
                                                    1. Temp is higher
                                                      1. the average particle energy will be higher- more particles have enough energy to escape
                                                      2. Density is lower
                                                        1. the forces between the particles will be weaker, and are thus easier to overcome
                                                        2. Surface area is larger
                                                          1. more particles near enough to the surface to escaoe
                                                          2. Airflow over the liquid is greater
                                                            1. The lower the amount of the evaporating substance in the surrounding air, the higher the rate of evaporation
                                                              1. a greater airflow means the liquid is replaced more quickly, so the concentration in the air will be lower
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