Abstract:

Thermodynamics is perceived by teachers and students to be difficult to teach, understand and apply, especially the second law. Baierlein [1] stated that, for both teacher and student, this step is terribly difficult. While reasoning, students easily lose sight of the overall context, and an intellectually satisfying understanding of what "entropy" represents remains unattainable [2-4].

In a survey Cochran et al [2] provided students with a number of situations featuring thermal machines that require energy exchange with several thermal sources. The analysis showed that students use the first law to answer the questions. Smith et al [5] also reported several specific student difficulties with the second law in the context of heat engines. The written data revealed that students do not make a clear link between the Carnot cycle and the second law after the lecture course. In another survey conducted after teaching the second law, Christensen et al [3] noticed that more than half of the students answered incorrectly using the conservation of entropy, Loverude [6] also examined students' reasoning about entropy and the second law. The outcome suggests that students do not use a single simple model of entropy, but rather a variety of conceptual resources (entropy conservation, order, disorder, multiplicity, probability etc.). Thus students frequently switch from one resource to another, which in some cases leads to contradictory predictions.

This work is based on two questionnaires submitted to samples of second year undergraduate French students after a semester of teaching thermodynamics. These studies highlight the difficulties encountered by the students which prevented them from tackling the problems related to the second law of thermodynamics in the best conditions. While some can be viewed as simple mistakes, others constitute real, profound obstacles which in certain situations prevail over the correct rationale. This may be due to common reasoning or confusion caused by insufficient understanding of concepts such as system, isolated system or closed system.

References:
[1] R. Baierlein, Am. J. Phys., 62 (1), p. 15-26, 1994.
[2] M. J. Cochran and P. R. L. Heron. Am. J. Phys., 74 (8), p. 734-741, 2006.
[3] W. M. Christensen, D. E. Meltze and C.A. Ogilvie. Am. J. Phys., 77(10), p. 907-917, 2009.
[4] M. Méheut, C. Duprez et I. Kermen. Didaskalia, n° 25, p. 31-61, 2004.
[5] M. Loverude. Phys. Rev. ST Phys. Educ. Res. 11, 020118 (2015).
[6] T. I. Smith, W. M. Christensen, D. B. Mountcastle, J. R. Thompson. Phys. Rev. ST Phys. Educ. Res. 11, 020116 (2015).

Keywords:

Thermodynamics, Fundamental laws, Entropy: balance computation, Systems: isolated / closed, Process: reversible / irreversible, Teaching thermodynamics.