I'm new to the forum, so please be kind. I was reading through my pchem textbook, and I noticed something. We're given the equation: ΔU = q + w For an adiabatic expansion, we're told that q = 0. Fair enough, no heat transfer. But when there is a constant T and change in V, my book says: ΔU = 0 (U is constant) I don't understand. W = -∫pdV, doesn't it? Why is work zero? The book also says that for a perfect gas, U isn't dependent on volume. When they use this fact, it makes sense why ΔU = 0, but it seems like a contradiction when using the definition of work. Also, the book continues and says: ΔU = CvΔT when V is constant. Again, W = -∫pdV, right? So dV = 0, shouldn't ΔU = 0? Thanks in advance!