Delta U？

[Sue Xu 2K]

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

[Angela G 2K]

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]

Also remember when under constant pressure

[Aditya Pimplaskar 1J]

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]

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]

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]

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]

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