A particle for Heat?

[swansont]

 

When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases. The motion and spacing of the particles determines the state of matter of the substance. The end result of increased molecular motion is that the object expands and takes up more space.

 

 

Except when it doesn't happen that way — some materials have negative coefficients of expansion. (Also, if you're going to copy/paste answers off the internet, you should cite the source)