## Internal Energy as State Function

$\Delta U=q+w$

Jasmine 2C
Posts: 184
Joined: Wed Sep 18, 2019 12:18 am

### Internal Energy as State Function

I know that the purpose of this image is to show that internal energy is a state function because the internal energy of both are the same, just that the path taken is different. However, what I'm wondering is how the volume of b expanded if there's no work done and no heat input.
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Deepika Reddy 1A
Posts: 125
Joined: Thu Jul 11, 2019 12:15 am

### Re: Internal Energy as State Function

The volume is expanding in b but it is expanding in a vacuum. What this means is that the external pressure is zero, so there is no force that is opposing the expansion being doing by the system. Work is only done when there is an opposing force that needs to be pushed against. Since there is no opposing force, there is no work done and therefore no change in the internal energy.