Final answer:
Entropy increases in irreversible processes often due to deviations from mechanical equilibrium, like pressure differences; while in reversible processes, such as those in equilibrium, entropy remains constant.
Step-by-step explanation:
The topic of entropy is deeply rooted in thermodynamics, especially in the context of understanding the second law of thermodynamics, which states that the total entropy of an isolated system can never decrease over time. Entropy can be thought of as a measure of the randomness or disorder of a system, and it provides insight into the direction of spontaneous processes and the efficiency of energy transformation processes. In the context of your question, doing work due to a pressure difference, such as in an irreversible process where there is a finite difference in pressure, can indeed generate entropy because such processes are not in mechanical equilibrium and typically increase the overall disorder of the system.
Conversely, processes that are reversible and maintain mechanical equilibrium, like the hypothetical PdV work done by an oscillating boundary, do not lead to an increase in entropy because the system moves through a sequence of equilibrium states. The discussion on work, like the expansion of a gas doing work against a piston in a cylinder, and its relationship with internal energy and heat adds another layer of complexity to understanding the energetics and entropy changes of such processes.
In summary, entropy is a measure of the dispersal of energy and when systems undergo irreversible processes, we often see an increase in entropy, reflecting the reduced ability to convert heat into work. However, for reversible processes wherein the system is perpetually in a state of mechanical equilibrium, entropy remains constant. These ideas underscore the fact that entropy is a central concept in determining the feasibility and efficiency of energy conversion processes.