Heat or thermal energy is an indication of how fast the molecules are moving in a substance. Temperature is a measure of how hot or cold a material is. It is a measurement of the movement of molecules in matter.When you measure temperature you are using the unit degrees.

A thermometer placed in water to determine its temperature. As heat energy is added to a material, the material’s temperature rises. As heat energy escapes from the material, the temperature of the material drops. The higher the temperature, the more rapid is the movement of the molecules in the matter, so the greater the space the molecules will occupy.

Nearly all materials expand (take up more space) when their temperature is increased and contract (take up less space) when their temperature is lowered.