Identifying student resources in reasoning about entropy and the approach to thermal equilibrium

[This paper is part of the Focused Collection on Upper Division Physics Courses.] As part of an ongoing project to examine student learning in upper-division courses in thermal and statistical physics, we have examined student reasoning about entropy and the second law of thermodynamics. We have examined reasoning in terms of heat transfer, entropy maximization, and statistical treatments of multiplicity and probability. In this paper, we describe student responses in interviews focused on the approach of macroscopic systems to thermal equilibrium. Our data suggest that students do not use a single simple model of entropy, but rather use a variety of conceptual resources. Individual students frequently shifted between resources, in some cases leading to contradictory predictions. Among the resources that students employed were some that have been previously described in the literature, including inappropriate use of conservation. However, our results suggest that student use of resources connected to disorder are neither simple nor monolithic. For example, many students used a previously unreported association between the equilibrium state of a system and an increase in order, rather than disorder.

Figure 1

The first page of the interview task. Students were asked to respond to the questions and explain their thinking. For the first set of four interviews, only three parts (A, D, and E) were used.

Figure 2

Second page of the interview prompt. Adapted from Christensen et al. [7].