## Delta U？

$\Delta U=q+w$

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

### Delta U？

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？

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？

Also remember $\Delta U=\Delta H+w$ when under constant pressure

Posts: 32
Joined: Thu Jul 13, 2017 3:00 am

### Re: Delta U？

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？

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？

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
Posts: 20
Joined: Fri Sep 29, 2017 7:05 am

### Re: Delta U？

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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Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

### Re: Delta U？

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