## Internal Energy in a Vacuum [ENDORSED]

$\Delta U=q+w$

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### Internal Energy in a Vacuum

Can someone explain why no work can be done through expansion in a vacuum? And why does this result in the values of both q and w to be zero?

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Joined: Sat Jul 22, 2017 3:00 am

### Re: Internal Energy in a Vacuum

No work can be done through expansion in a vacuum because work is defined as -P*deltaV.
In a vacuum, there is no opposing force, so therefore the work done is 0. The book defines this as free expansion on page 264.

Julia Cheng 2J
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### Re: Internal Energy in a Vacuum

Also, q is zero in free expansion because no heat exchange occurs between the system and surroundings.

Paula Sing 1J
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### Re: Internal Energy in a Vacuum

I think that the idea of a vacuum is that there is no pressure in the system, thus the energy change is zero because in the equation w=-p(delta)t the value for p is always zero, so q=0 as well.

aaron tang 2K
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### Re: Internal Energy in a Vacuum

since work is defined as w = -P DELTA V, and because it is in a vacuum there is no opposing force that is occurring which results in no work.

Scout_2C
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### Re: Internal Energy in a Vacuum  [ENDORSED]

Same applies if say a question was to mention something happening in space as well.