The expansion or compression of gas confined in a piston-and-cylinder device is a classic working example used for illustrating the First and Second Laws of Thermodynamics. The balance of energy and entropy enables the estimation of a number of thermodynamic properties. The entropy generation (also called entropy production) resulting from this process can also be used to determine the feasibility and reversibility of a process. In this work, we present an extended discussion involving quantitative analysis of the effects of friction between a piston and the interior wall of a cylinder. Our findings indicate that the friction force caused by the movement of the piston is a main source of entropy generation in this process. This explanation does not appear in most textbooks dealing with similar problems. We also discuss, from a quantitative perspective, the effects of friction on the dynamic physical and thermodynamic properties, including entropy generation. Our findings suggest that engaging students in a discussion related to piston-and-cylinder problems involving the effects of friction could provide valuable insight into entropy generation in practical applications.