Introductory statistical mechanics is studied for a simple two-state system using an inexpensive and easily built apparatus. A large variety of demonstrations, suitable for students in high school and introductory university chemistry courses, are possible. This article details demonstrations for exothermic and endothermic reactions, the dynamic nature of equilibrium, and Le Châtelier's principle. The demonstrations show how the equilibrium changes as the temperature, energy, and entropy are varied.
Supplement
The details of construction and operation of the apparatus, including an exploded view of the apparatus, are available. Also available are an elementary development of the Boltzmann distribution law using quantitative data obtained from the apparatus, and time-dependent demonstrations using a simple attachment.
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