# Heat and Heat Transfer

Heat and Heat Transfer

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• Created by: Scott
• Created on: 05-02-11 16:03

## Heat and Temperature

• Heat is the amount of thermal energy something has.
• It is measured in Joules or Kilojoules (J or KJ).
• Temperature is a measure of how hot or cold something is.
• It is measured in degrees C.
• Specific heat is the amount of joules needed to raise 1g of a substance 1 degrees C.
• Heat transfer is always from hot to cold.
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## Conduction

• Conduction can take place in a solid, liquid or gas.
• It is the main method of heat transfer in solids.
• Gas and liquids are not good conductors of heat as their particles are spread out.
• In conduction heat energy is turned in to kinetic energy.
• This makes particles vibrate which hit their neighbours and this happens all the way from the heat source to the cold end of the substance.

• Level F
• Metals contain free electrons which do not belong to a specific atom.
• The atom without the electron is a charged metal ion. The electrons hit into the ions which makes them vibrate even more.
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## Convection

• Convection can only take place in a liquid or a gas as the particles in a solid only vibrate they do not move.
• Heaters use convection to heat rooms.
• The heater heats the air around it which rises as it becomes less dense than the air above it.
• As this air moves up cold air takes its place.
• This air is then heated so it rises then cools, becomes denser that the air below it and sinks where it is heated again.
• This is called a convection current and it takes place in the sun.
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• Radiation is the only method of heat transfre that does not require a substance to travel through.
• Radiation is transfered by electromagnetic waves.
• The waves are infrared waves.
• Infrared waves have a wavelength between 0.72 and 10 micrometers.
• Shiny silvery surfaces reflect radiation the best while dark surfaces absorb the best.
• All things emmit radiation but the larger the mass the more radiation absorbed and emmited.