Limitations and functions: Four examples of integrating thermodynamics

The literature has argued that students usually learn physics principles discretely. They tend to be unaware of the functions and limitations, i.e., the why and why not, of using individual principles, and are inclined to adopt “hot formulas” inappropriately. For example, when explaining the adiabatic compression of an ideal gas, few students can invoke the concept of "work" (i.e., the 1^st Law) to justify a change in temperature (Loverude, Kautz, and Heron, 2002). When explaining processes involving temperature variation, students tend to adopt the ideal-gas law (PV=nRT) but ignore some relevant variables (Loverude, Kautz, and Heron, 2002; Rozier and Viennot, 1991). In order to help students distinguish the functions and limitations of the related theories of a physics topic, and meaningfully grasp the topic as a whole, the literature (Buncick, Betts and Horgan, 2001; Chang, 2011) has suggested developing a series of real-life examples and engaging students in thinking and discussion.

This paper introduces four examples for bridging five principles, from fluids to thermodynamics, including (1) buoyant force, (2) thermal expansion, (3) the ideal-gas law, (4) the 1^st law, and (5) kinetic theory. The sequence of the five topics is fairly consistent with those which appear in undergraduate introductory textbooks. With respect to each example, both major effective theories and prevalent inappropriate reasoning are addressed. Thus, pedagogically, the examples play the dual roles of demonstrating the limitations of the prior principles and highlighting the functions of those principles that follow.