## U and its relations to work

Julia Go 2L
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Joined: Sun Sep 30, 2018 12:17 am
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### U and its relations to work

What does the variable U stand for and what is its relation to work?

Cynthia Aragon 1B
Posts: 47
Joined: Mon Apr 09, 2018 1:38 pm

### Re: U and its relations to work

U, stands for the internal energy of a system which can be altered by heat flow and work.
If heat flows into the system; work is done on the system, and its internal energy increases, ΔU > 0.
If heat flows out of the system, work is done by the system, and its internal energy decreases, ΔU < 0

Hope this helps!

Annalyn Diaz 1J
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Joined: Fri Sep 28, 2018 12:15 am

### Re: U and its relations to work

Additionally in a closed system, internal energy relates to work in this equation:

delta U = q + w

Danny Zhang 4L
Posts: 62
Joined: Fri Sep 28, 2018 12:26 am

### Re: U and its relations to work

U represents the internal energy of a system. Its relation to work can be seen in the first law of thermodynamics: change in U = q(heat exchanged) + w(work done on or by the system).

Lopez_Melissa-Dis4E
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Joined: Fri Sep 28, 2018 12:20 am

### Re: U and its relations to work

The equation that relates U to work is delta U= q+w, U represents the change in internal energy.

Sydney To 1D
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Re: U and its relations to work

U is a state property and is the internal energy of a system. Changes in internal energy are a function of work. The energy of a closed system can be changed by heating/cooling or compression/expansion. $\Delta$U=q + w. If $\Delta$ V is zero (constant volume), delta U= $q_{v}$. If $\Delta$P=0 (constant pressure), then $\Delta$U=$\Delta$H-P$\Delta$V.

Jordan Lo 2A
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### Re: U and its relations to work

What is the difference between q and delta H?

Eruchi Okpara 2E
Posts: 53
Joined: Fri Sep 28, 2018 12:28 am

### Re: U and its relations to work

Additionally, when do you know whether to use q or delta H?