U and its relations to work

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Julia Go 2L
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U and its relations to work

Postby Julia Go 2L » Fri Feb 01, 2019 8:50 am

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

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

Re: U and its relations to work

Postby Cynthia Aragon 1B » Fri Feb 01, 2019 8:55 am

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

Postby Annalyn Diaz 1J » Fri Feb 01, 2019 11:21 am

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

delta U = q + w

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

Re: U and its relations to work

Postby Danny Zhang 4L » Fri Feb 01, 2019 1:32 pm

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

Postby Lopez_Melissa-Dis4E » Fri Feb 01, 2019 1:35 pm

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

Sydney To 1D
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Re: U and its relations to work

Postby Sydney To 1D » Fri Feb 01, 2019 1:43 pm

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. U=q + w. If V is zero (constant volume), delta U= . If P=0 (constant pressure), then U=H-PV.

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

Postby Jordan Lo 2A » Sat Feb 02, 2019 12:35 pm

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

Postby Eruchi Okpara 2E » Sat Feb 02, 2019 7:54 pm

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

MadelynNguyen1F
Posts: 59
Joined: Fri Apr 06, 2018 11:04 am

Re: U and its relations to work

Postby MadelynNguyen1F » Sat Feb 02, 2019 8:20 pm

Delta H is enthalpy while q is heat flow.


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