## Delta U (Concept Clarification)

$\Delta S = \frac{q_{rev}}{T}$

Frenz Cabison 1B
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Joined: Fri Sep 29, 2017 7:07 am

### Delta U (Concept Clarification)

Why does gas expand if delta U is zero? I quite don't understand the concept behind this statement.

Masih Tazhibi 2I
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Joined: Fri Sep 29, 2017 7:06 am

### Re: Delta U (Concept Clarification)

While the internal energy is zero, the gas is expanding against a vacuum which has no resistance.

Niyanta Joshi 1F
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### Re: Delta U (Concept Clarification)

There is no net change in internal energy as all the heat is used to to do expansion work against the surroundings.

Nora Sharp 1C
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### Re: Delta U (Concept Clarification)

viewtopic.php?f=130&t=26453

Helen Shi 1J
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### Re: Delta U (Concept Clarification)

In what cases is delta U=0? Why is delta U zero in an isothermal expansion?
Last edited by Helen Shi 1J on Mon Feb 05, 2018 12:10 pm, edited 1 time in total.

Wenjie Dong 2E
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### Re: Delta U (Concept Clarification)

There is no change in internal energy in the system when delta U=0.

Sophia Kim 1C
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### Re: Delta U (Concept Clarification)

I think I read in the book that delta U is 0 because the molar internal energy of an ideal gas is U=3/2 RT and since internal energy and temperature are state dunctions DeltaU = 3/2 R DeltaT. So in an isothermal expansion where delta t = 0 , DeltaU would equal 0 as well.