The laboratory experiment described provides insight into the energetics of hydrogen evolution at an electrode as well as the intrinsic barrier that typically impedes reaction. In the course of the exercise, students find that Sn(s) is thermodynamically capable of combining with protons to form hydrogen, but that the direct reaction occurs at a negligible rate in the absence of an applied overpotential or a suitable catalyst. Exploring the latter option, students fabricate mini-cells with tin as the anode and either copper or platinum as the cathode. Upon immersing the assemblies in HCl(aq), they observe vigorous formation of H[subscript 2](g), but only when tin and platinum electrodes are present. They also detect a change in mass that is attributable to the loss of tin, and they attempt to reconcile the stoichiometry of reaction. The exercise requires minimal equipment and provides useful insight into processes that are potentially important to the future energy economy.