The paper revisits Rüchardt’s experiment and the two-chamber variant of Clark and Katz, where the
oscillating motion of a freely sliding piston involves the adiabatic exponent of the gas enclosed in
a thermally isolated chamber. While the common theoretical account of the experiment correctly
predicts the frequency of the oscillation, the damping is usually ascribed to a linear frictional
force of an undetermined mechanical nature. In this paper, we argue that the irreversibility of the
damped motion calls for a thermodynamical treatment involving dissipation (entropy production). The
theory of Rüchardt’s experiment is reworked at the undergraduate level by allowing entropy to change
owing to heat transfer into or out of the chamber. It is calculated that a linear heat transfer can
explain the observed damping without assuming any mechanical friction. The calculation is
quantitatively supported by an experiment. It is also calculated that the mechanical and thermal
equilibrations…