Do all solids expand upon heating? To most people's surprise, there is a class of rather common solids, namely rubbery elastic polymers, capable of contracting upon heating1,2 while staying in the same solid phase. This seems contradictory to common sense and the physical theories of thermal behavior of ordinary solids. The physical behavior of elastic polymers continues to amaze physics and chemistry students as well as many scientists, despite the fact that it was experimentally detected in natural rubbers two centuries ago. For the following 125 years this phenomenon remained unexplained. An explanation was finally found only in the 1930s when the new science of “polymer physics” emerged. The goal of this paper is to demonstrate that some elements of polymer physics can be useful in teaching introductory general physics, especially in discussing the thermal properties of solids and for introducing the concept of entropy. Initially, several simple demo∕lab experiments manifesting the extraordinary thermal properties of rubbers will be discussed. A brief description of the search for an explanation of the physics underlying this behavior will follow. The discussion will include the macromolecular hypothesis of Staudinger,3 the notion of a conformational state of a macromolecule, and the idea of statistical probabilities for the end-to-end macromolecular distances.1,2,4 The latter leads directly to an explanation of the emergence of the entropic force that is responsible for contraction upon heating. These notions are shown to be easily employable for introducing the idea of entropy to a beginner.