  Entropy is a difficult concept to teach using real-world examples. Unlike
temperature, pressure, volume, or work, it's not a quantity which most students
encounter in their day-to-day lives. Even the way entropy is often
qualitatively described, as a measure of disorder, is incomplete and can be
misleading. In an effort to address these obstacles, we have developed a simple
laboratory activity, the stretching of an elastic rubber sheet, intended to
give students hands-on experience with the concepts of entropy, temperature and
work in both adiabatic and quasistatic processes. We present two versions of
the apparatus: a double-lever system, which may be reproduced with relatively
little cost, and a commercial materials testing system, which provides students
experience with scientific instrumentation that is used in research.
