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Dulong and Petit's Law: We Should Not Ignore Its Importance

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Mary Laing and Michael Laing

Durban 4001, Republic of South Africa

J. Chem. Educ., 2006, 83 (10), p 1499

DOI: 10.1021/ed083p1499

Publication Date (Web): October 1, 2006

Section:

History, Education, and Documentation

Abstract

Dulong and Petit's law played an important role in the development of the periodic table as Mendeleyeff used this method in 1870 to correct the atomic weights of indium, cerium, and uranium that were wrong in the table of 1869. The discontinuous variation of molar heat capacity of a solid with change in temperature can be due to a phase change, order–disorder phenomena, or magnetic transitions. Two student exercises are described: the determination of the specific heat of a metal and hence its atomic weight (lab experiment) and a graphical study of specific heat versus atomic weight for different groups of metals and the confirmation of Dulong and Petit's law (classroom activity). The molar heat capacity is shown to be close to 26 J mol^-1 K^-1 for the solid elements. The anomalously low values for Be, B, C, and Si are explained by the Debye theory. The large value for Gd is shown to be a result of its magnetic properties; its Curie temperature is close to room temperature. The exercises are suitable for the general chemistry course.

Keywords (Audience):

First-Year Undergraduate / General

Keywords (Domain):

History / Philosophy

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Calorimetry / Thermochemistry

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This article has been cited by 2 ACS Journal articles (2 most recent appear below).

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