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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 7 Issue 2 (2002) pp 61-65

Entropy and the First Law of Thermodynamics

Panos Nikitas

Laboratory of Physical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece
Received January 25, 2002. Accepted February 27, 2002

Published online: 15 March 2002

Abstract. Planck’s work on the Second Law of Thermodynamics in combination with a simple thermodynamic approach developed by Blinder show that the concept of entropy is introduced from the First and not the Second Law of Thermodynamics. In particular, it is proved that the First Law of Thermodynamics leads directly to the following statement: For every system of whatever complexity there exists an extensive function of state S defined from dS =qrev/T, where qrev is the infinitesimal quantity of heat exchanged reversibly between the system and the surroundings and T is the absolute temperature of the system. Thus, for reversible adiabatic processes we readily have from the First Law that dS = 0. Therefore, the Second Law should be properly reformulated, restricted to the inequality dS > 0 for irreversible processes only.

Key Words:  In the Classroom; physical chemistry; thermodynamics; first law of thermodynamics; second law of thermodynamics; entropy

(*) Corresponding author. (E-mail: nikitas@chem.auth.gr)

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[Editor note: Please see John C. Wheeler's article concerning this manuscript.]


Issue date: April 5, 2002

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