  We focus on the study of the processes undergone by a perfect gas when the
external pressure is suddenly modified. The analysis shows that, from the
second law perspective, there is a non-evident asymmetry between the processes
of compression and expansion between the same pressures, which is manifested
through different levels of entropy production. If the system remains in
contact with a thermal reservoir during the processes this asymmetry is
remarkable, since while entropy grows linearly with the relative change of
pressure during the compression, the relation between those variables is
logarithmic during the expansion.
