Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jammie001 on 21/09/2011 03:03:19

Title: When matter is compressed, does it always become hotter?
Post by: jammie001 on 21/09/2011 03:03:19

When matter is compressed, does compression always generate heat?

Title: Re: When matter is compressed, does it always become hotter?
Post by: Pmb on 21/09/2011 04:50:11

Quote from: jammie001 on 21/09/2011 03:03:19

When matter is compressed, does compression always generate heat?

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

Title: Re: When matter is compressed, does it always become hotter?
Post by: Soul Surfer on 21/09/2011 09:09:53

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.

Title: When matter is compressed, does it always become hotter?
Post by: chris on 21/09/2011 09:15:20

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.

Title: When matter is compressed, does it always become hotter?
Post by: imatfaal on 21/09/2011 10:26:27

Those substances that have a  piezoelectric property  (http://en.wikipedia.org/wiki/Piezoelectricity)might also accumulate an electric charge when compressed.

Title: When matter is compressed, does it always become hotter?
Post by: Bored chemist on 22/09/2011 07:00:03

Quote from: Pmb on 21/09/2011 04:50:11

Quote from: jammie001 on 21/09/2011 03:03:19

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.

Title: When matter is compressed, does it always become hotter?
Post by: Geezer on 22/09/2011 07:14:40

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?

Title: When matter is compressed, does it always become hotter?
Post by: lightarrow on 22/09/2011 13:01:24

Quote from: jammie001 on 21/09/2011 03:03:19

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

Quote

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.

Title: When matter is compressed, does it always become hotter?
Post by: Bored chemist on 22/09/2011 20:12:34

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.