Different ways to calculate change in U

[ashwathinair]

How do you calculate the change in U for different situations: constant/changing pressure, temperature, volume etc?

[Jared_Yuge]

In a closed system with no constants its just delta U = q +w

[Jared_Yuge]

If delta V is 0 (constant volume) then its just deltaU = q

[Jared_Yuge]

if delta P is 0 (under constant pressure) then delta U = delta H - P deltaV

[Jared_Yuge]

This is assuming it is an open or closed system with a piston, where heat and compression/expansion change, but in an isolated system the delta U is just q + w =0 because the point of an isolated system is that the internal energy doesn't change