Heat and Temperature
Heat is a type of energy that will flow from a warm area to a colder one. For example…
This cup of coffee will cool down because it is giving out heat energy into the surroundings.
This drink (taken out of the fridge) will warm up because it is taking in heat energy from the surroundings.
Conduction is all about when heat is transferred through solids. The heat is passed on by vibrationsin the molecules. These vibrations get BIGGER when the solid has more ENERGY (i.e. when it is being heated).
Metals are better conductors than non-metals. This is because the heat is carried by free electrons that can carry the energy around the metal and give it to other electrons and ions.
Convection is all about when a gas or liquid (“fluid”) moves and carries heat with it. When the fluid is heated it expands.
This means that it will become less dense than the colder fluid around it.
Because of this the warmer fluid will try to rise over the colder fluid, and this is why warm air rises.
This is called a convection current.
This is how heat reaches us from the radiators in this room.
Conduction and Convection
In CONDUCTION the heat was passed on by VIBRATIONS in a SOLID
In CONVECTION the heat is passed on by the FLUID expanding, rising and TAKING THE HEAT with it
I’m very hot!
Radiation is when heat moves around in electromagnetic waves like light does.
Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called infra-red.
Dark, matt colours will absorb AND emit the most infra-red radiation, and light, shiny colours will reflectit.
Anything HOT emits HEAT RADIATION – the hotter it is, the more infra red radiation it emits