A simple model of thermal expansion

A simple ball and spring model of thermal expansion suitable for non-calculus-based introductory physics courses is presented. With this model it is possible to correctly predict a change in length proportional to the change in temperature. This is done without the need to introduce a thermal average over a Boltzmann distribution, but instead using the theorem of the equipartition of energy. The model also focuses attention on the need for an asymmetric interatomic potential even though the average atom finds itself in a symmetric potential well.