Why does a gas get colder when it expands?

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Offline mike2niner4

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Why does a gas get colder when it expands?
« on: 28/09/2009 13:30:03 »
Michael Perry  asked the Naked Scientists:
   
Hello Naked Scientists!
 
I am wondering if you can explain to me why when a gas expands, it gets colder?
 
Love the show and many thanks,
 
Michael Perry from Northwich

What do you think?

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Offline Vern

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Why does a gas get colder when it expands?
« Reply #1 on: 28/09/2009 13:56:47 »

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Offline Turveyd

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Why does a gas get colder when it expands?
« Reply #2 on: 28/09/2009 23:43:15 »
Because the Heat Energy which was contained in the gas is spread over a larger area so less heat energy at any point.

Also with can's of compressed gas ( deodorant say ) when you compress the gas into the can,  the can heats up and then losses that heat,  so the gas comes out at room temperature and then expands as above.