Can I lower temperature by reducing volume?

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Offline Liskow

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Can I lower temperature by reducing volume?
« on: 13/03/2009 17:26:10 »
Hot things tend to be a little larger than cold things.  So can I lower a things temperature by squishing it into a smaller volume?

Mod edit - Please make your subjects as the question you wish to ask.  This makes the forum tidier and easier to navigate, Thanks!
« Last Edit: 16/03/2009 09:46:34 by BenV »

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Offline lancenti

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Re: Can I lower temperature by reducing volume?
« Reply #1 on: 13/03/2009 18:05:12 »
This is not necessarily true.

Unit mass of water at 4 degrees centigrade has a smaller volume than unit mass of water at 1 degree centigrade, if I remember right. Water is densest at 4 degrees I believe.

However, using the ideal gas law,

pV=nRT

or Charles Law (I believe)

V1/T1=V2/T2

We find that compression should actually lead to an increase in temperature. Hence to cool a gas, you'd probably want to rapidly expand it.

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blakestyger

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Re: Can I lower temperature by reducing volume?
« Reply #2 on: 13/03/2009 18:37:45 »
We find that compression should actually lead to an increase in temperature. Hence to cool a gas, you'd probably want to rapidly expand it.

Yep - the Joule-Thompson effect.

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Offline lightarrow

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Re: Can I lower temperature by reducing volume?
« Reply #3 on: 14/03/2009 10:55:24 »
Hot things tend to be a little larger than cold things.  So can I lower a things temperature by squishing it into a smaller volume?
Even if your first sentence were always true (but it's not) it's wrongly stated:
when you *give heat* to things they enlarge. Infact, if you compress them, you *receive heat* from them.
« Last Edit: 14/03/2009 10:59:39 by lightarrow »

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Offline Raghavendra

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Re: Can I lower temperature by reducing volume?
« Reply #4 on: 16/03/2009 09:36:59 »
hmmm you are at critical

          You should read raoult's law