Delta U?


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Sue Xu 2K
Posts: 58
Joined: Fri Sep 29, 2017 7:06 am

Delta U?

Postby Sue Xu 2K » Thu Jan 18, 2018 8:52 pm

We talked about delta U in class. Could some one please explain to me again what exactly it is?

Angela G 2K
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

Re: Delta U?

Postby Angela G 2K » Thu Jan 18, 2018 9:02 pm

Delta U is the change in internal energy due to the transfer of energy as work and/or heat. Delta U = q + w

Sarkis Sislyan 1D
Posts: 31
Joined: Thu Jul 27, 2017 3:00 am

Re: Delta U?

Postby Sarkis Sislyan 1D » Thu Jan 18, 2018 9:04 pm

Also remember when under constant pressure

Aditya Pimplaskar 1J
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Joined: Thu Jul 13, 2017 3:00 am

Re: Delta U?

Postby Aditya Pimplaskar 1J » Fri Jan 19, 2018 12:16 am

Just like the previous replies state, ΔU is the change in internal energy of the system. To add on to what the previous replies said, you can think of U as the kinetic energy + potential energy of the particles that your sample is comprised of.
Internal energy is a state function, like enthalpy. It is also dependent on temperature (also a state function); this is due to the proportional relationship between temperatures of gases and average kinetic energy of particles (this KE contributes to U, or the internal energy).

RohanGupta1G
Posts: 34
Joined: Sat Jul 22, 2017 3:00 am

Re: Delta U?

Postby RohanGupta1G » Fri Jan 19, 2018 8:25 am

I believe the delta symbol always means change in the given variable which in this case is U(final)-U(initial)=(delta) U. U is the energy of the system.

Sarah Sharma 2J
Posts: 33
Joined: Fri Sep 29, 2017 7:05 am

Re: Delta U?

Postby Sarah Sharma 2J » Fri Jan 19, 2018 10:20 am

Delta U is referred to as the change in internal energy of a system. Delta U is actually equal to q + w whereas q is the heat input or Delta H. w= -P(Vfinal-Vinitial). If in a problem the system has a constant volume and no expansionary work is performed then w=0.

Susie Lee 2I
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Joined: Fri Sep 29, 2017 7:05 am

Re: Delta U?

Postby Susie Lee 2I » Sat Jan 20, 2018 4:10 pm

Adding onto the previous posts, if delta u is positive, then u(final) > u(initial). If delta u is negative, then u(final) < u(initial).

Diego Zavala 2I
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Re: Delta U?

Postby Diego Zavala 2I » Sun Jan 21, 2018 8:43 pm

U is the internal energy of the system. Because the internal energy of a molecule would consist on the summation on the energies within atoms, bonds, etc (too complex to calculate), we use Delta U to discuss the change in the internal energy of a system without having to know the actual numerical value of the internal energy


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