We describe an upper-division experiment in thermal physics where students measure the tension of a rubber band as a function of temperature and length and use a Maxwell relation to find the change in internal energy and entropy for an isothermal stretch. This allows students to experimentally check the predictions of the entropic spring model for elastomers and observe that the entropy does indeed decrease as a rubber band is stretched.
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Webpage of the Paradigms in Physics project, <http://physics.oregonstate.edu/portfolioswiki/>.
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2013
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