We are currently learning about isothermal processes in class and there's something i don't really get. i can visualize what happens when the piston is pulled or pushed very slowly, PV = constant and hence produces an isotherm on a PV diagram. And if since the temperature is constant, there isn't any change in internal energy and Q = W. However, i can't visualize this process. To my understanding, if heat is added to the system, internal energy increase, then the system does work and the volume expands. isn't this more like an isobaric process. How can the temperature keep constant, (also given that the walls of the piston are thermally insulted)? In other words, what i don't get is how does q = w, reduce the temperature to its original when q is heat added to the system. is q converted directly into w? How? really can't visualize.