If you want to use mass-equivalence (http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence)

Quote:

Whenever energy is added to a system, the system gains mass.

Raising the temperature of an object (increasing its heat energy) increases its mass. For example, consider the world's primary mass standard for the kilogram, made of platinum/iridium. If its temperature is allowed to change by 1°C, its mass will change by 1.5 picograms.


Temperature can mean many things to a scientist but the most essential is the hotter something gets the more energy it has within it.

Thus to heat a body up you add energy to cool something down you remove energy.


Last edited by Orac; 08/26/11 02:53 AM.
I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.