My textbook says, basically, for an adiabatic process... All three variables in the ideal gas law—P, V, and T—change during an adiabatic process. Let’s imagine an adiabatic gas process involving an infinitesimal change in volume dV and an accompanying infinitesimal change in temperature dT. The work done by the gas is W=PdV. Question: if P, V, and T are all changing, should the infinitesimal work be: W=PdV+VdV and not simply W=PdV I've seen pretty much the same treatment in other textbooks and online, and finally decided to try to find out hat I'm missing here. Any ideas?