In the adiabatic expansion step of carnot cycle, adiabatic change is carried out in an insulated system. In this process volume gets increased but entropy remains constant.
Now if we look at the concept (as far as I know) of entropy, it determines the number of arrangement in which gas particles can remain within the container/box. Since the volume increased, shouldn't this number of arrangement increase and a change in entropy take place? I know there is no exchange of heat but as far as I know entropy is concerned with the number of arrangement. So why entropy of an isentropic process remains constant?