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Strictly speaking, a system at equilibrium cannot change; hence, even
speaking theoretically, isobaric, isochoric, isothermal, isentropic
processes are nonequilibrium processes even in the ideal.
But they
can be described "as if" passing through a series of "equilibrium
states" if they are assumed to be infinitesimally close to equilibrium
throughout the process. In reality this would necessitate that they
occur infinitely slowly. Real processes do not occur infinitely
slowly and, thus, are not infinitesimally close to equilibrium.
However, real gases achieve equilibrium very quickly, which is why
equilibrium thermodynamics describes such nonequilibrium processes so
well.
To test your understanding of equilibrium thermodynamics, consider
this question: Water is supposed to boil at 100 deg C at 1 atmosphere
pressure. But, if so, can you explain to a student why water
evaporates at room temperature?
Finally, to pick a nit, thermodynamic states are not static
equilibrium states. Even exactly at equilibrium, they are quite
dynamic -- exchanging energy between molecules, transferring energy
and molecules from one part of the volume to another. Even the
average values of entropy, pressure, density, internal energy, etc.
are not "static". They fluctuate about average values, and the
magnitudes of the fluctuations are inversely proportional to the
number of particles.