Heat and Heat Transfer

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 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 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.
This type of radiation is called thermal radiation.

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