[jammie001 (OP)]

When matter is compressed, does compression always generate heat?

[Pmb]

When matter is compressed, does compression always generate heat?

Yes, I believe so. I can't think of a counter example at the moment

[Soul Surfer]

Yes, always, because you are working against what ever it is you are compressing's rigidity and tendency to expand so you are putting energy into it so it must get hotter.

[chris]

Exactly as Soul Surfer says, you are doing work against the material and therefore increasing its energy; the counter-example is the expansion of a compressed gas, like a deodorant can sprayed in the armpit, which becomes cold because the gas is "doing work" against the atmosphere and therefore losing energy in the process.

[imatfaal]

Those substances that have a piezoelectric property might also accumulate an electric charge when compressed.

[Bored chemist]

When matter is compressed, does compression always generate heat?

Yes, I believe so. I can't think of a counter example at the moment

I think I can but I will have to check.

[Geezer]

What about water? It expands as heat is removed while it solidifies. Does that mean it gets hotter if you decompress it and vice-versa?

[lightarrow]

When matter is compressed, does compression always generate heat?

If with "compression" you can include "relaxation" of a material which has been stretched, than it's a rubber band:

http://en.wikipedia.org/wiki/Rubber_band

An interesting effect of rubber bands in thermodynamics is that stretching a rubber band will cause it to release heat (press it against your lips), while releasing it after it has been stretched will lead it to absorb heat, causing its surroundings to become cooler.

[Bored chemist]

Lightarrow checked my idea for me.
Thanks.
A stretched rubber band will get hotter if you compress it.
Ice will get colder if you compress it and thereby force it to melt.