p2 energy transfer by heating

• Solids transfer thermal energy by conduction
• Metals are the best conductors of thermal energy- they have higher thermal conductivity
• non-metals are poor conductors of heat - they are called insulators
• as particles are heated they vibrate faster
• the vibrations of heated particles are passed through a material
• in metals free (delocalised) electrons can also carry the energy which is why they are good conductors
• in non-metals there are no free electrons so less thermal energy is transferred
• a good insulator will keep you warm in the winter and cool in the summer
• insulators need to have a low thermal conductivity to keep energy transfer as low as possible
• aluminium is a good conductor
• stainless steel is a bad conductor
• and ion is an atom which has lost or gained electrons
• all objects emit infrared radiation due to their thermal energy
• the hotter an object is the more infrared radiation it emits
• thermal energy is also called heat and is measured in joules (J)
• temperature is how much energy there is per molecule
• infrared radiation travels as a wave and can pass through a vacuum
• the specific heat capacity of an a substance is how much energy it requires to raise 1kg by 1 degree celsius
• the specific heat capacity compares how quickly different objects heat up
• a storage heater uses electricity at night (when it is cheaper to heat bricks of concrete)
• a storage heater heats bricks which transfer energy to the room to keep it warm because the bricks have a high specific heat capacity so can store lots of energy and slowly give off the heat
• solar panels save money because no fuel is needed to heat the water but they are expensive to buy and instal
• payback time is how long it takes to make back the up-front costs of something
• double glazing and insulation reduce energy loss and save energy
• solar panels are flat boxes containing copper pipes on a matt black metal plate. a transparent cover on the top of the panel allows solar radiation through to heat up the plate. insulation under the plate stops energy being transferred. the energy is used to heat water in a storage tank