## internal energy

$\Delta U=q+w$

EMurphy_2L
Posts: 128
Joined: Sat Sep 07, 2019 12:16 am

### internal energy

so does ΔU = ΔH at constant pressure and constant volume?

Elena Bell 1C
Posts: 64
Joined: Thu Jul 11, 2019 12:16 am

### Re: internal energy

If a system is a constant pressure and volume then w would equal zero. Since, deltaU=q+w and q=deltaH I think it would just be deltaU=deltaH if both pressure and volume is constant.

Noe BM 1J
Posts: 50
Joined: Sat Sep 07, 2019 12:17 am

### Re: internal energy

This is because there's no expansion since pressure and volume are constant, right?

Elena Bell 1C wrote:If a system is a constant pressure and volume then w would equal zero. Since, deltaU=q+w and q=deltaH I think it would just be deltaU=deltaH if both pressure and volume is constant.

DLee_1L
Posts: 103
Joined: Sat Aug 17, 2019 12:17 am

### Re: internal energy

Yes, I believe that if the system is under both constant V and P (however, I think there will only be questions with one or the other) the change in internal energy will equal the change in enthalpy. And since P and V don't change, there is no expansion. However, there are cases when P and V are constant and the system still expands (like in a vacuum).

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