Stretching Rubber, Stretching Minds: a polymer physics lab for teaching entropy

TL;DR

This paper introduces a hands-on laboratory activity using rubber stretching to help students understand entropy, temperature, and work in thermodynamics through practical experiments, addressing common teaching challenges.

Contribution

It presents a simple, cost-effective rubber stretching apparatus and a more advanced commercial system for teaching entropy and related concepts experimentally.

Findings

Students gain intuitive understanding of entropy.

The activity demonstrates adiabatic and quasistatic processes.

Enhanced engagement in thermodynamics learning.

Abstract

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.