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U and its relations to work

Posted: Fri Feb 01, 2019 8:50 am
by Julia Go 2L
What does the variable U stand for and what is its relation to work?

Re: U and its relations to work

Posted: Fri Feb 01, 2019 8:55 am
by Cynthia Aragon 1B
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!

Re: U and its relations to work

Posted: Fri Feb 01, 2019 11:21 am
by Annalyn Diaz 1J
Additionally in a closed system, internal energy relates to work in this equation:

delta U = q + w

Re: U and its relations to work

Posted: Fri Feb 01, 2019 1:32 pm
by Danny Zhang 4L
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).

Re: U and its relations to work

Posted: Fri Feb 01, 2019 1:35 pm
by Lopez_Melissa-Dis4E
The equation that relates U to work is delta U= q+w, U represents the change in internal energy.

Re: U and its relations to work

Posted: Fri Feb 01, 2019 1:43 pm
by Sydney To 1D
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.

Re: U and its relations to work

Posted: Sat Feb 02, 2019 12:35 pm
by Jordan Lo 2A
What is the difference between q and delta H?

Re: U and its relations to work

Posted: Sat Feb 02, 2019 7:54 pm
by Eruchi Okpara 2E
Additionally, when do you know whether to use q or delta H?

Re: U and its relations to work

Posted: Sat Feb 02, 2019 8:20 pm
by MadelynNguyen1F
Delta H is enthalpy while q is heat flow.