KJEMI nr. 2 - 2020

2 2 K J E M I 2 2 0 2 0 Background Traditionally, there are two schools of thought in classical thermodynamics, which in line with the ground-breaking books in physical chemistry by Atkins are termed the traditional approach and the molecular approach (Atkins and De Paula, 2006, see preface ix). Briefly, in the traditional approach, equilibrium thermo- dynamics is introduced as a set of basic laws without explicit reference to the underlying molecular properties (such as moment of inertia, mass, or vibrational frequencies). The molecular approach is based on statistical thermodynamics, which requires some basic knowledge of quantum mechanics, particular- ly the concept of discrete energy levels, and from which classical thermodynamics can be derived to a large extent. Both approaches are valid and have their own merits. It is fair to say that the traditional approach is dominating the teaching of thermodynamics, likely for historical reasons. We will here argue that the molecular approach can be successfully used in basic 2 nd -year physical chemistry courses given to chemistry and chemical engineering stu- dents, provided they have a suitable backgro- und in quantum mechanics as well as statistics. We always need to choose a level of theory to describe experimental systems. As che- mists, we are rarely interested in the physics of the atomic nuclei in terms of its constitu- ents, but rather a level of theory dealing with Teaching basic classical thermodynamics through statistical thermodynamics – thermodynamics kept simple Summary: The teaching of basic classical thermodynamics through the introduction of statistical thermodynamics is discussed. Many phenomena and properties central in physical chemistry such as surface tension, phase coexistence and adsorption at surfaces as well as colligative properties as the osmotic pressure and boiling-point elevation by a solute, require the understanding of the chemical potential. These properties and many others can be qualitatively introduced within a common framework using relatively simple lattice models, which can be addressed using standard combinatorics, linking the thermodynamic properties to molecular properties such as molecular interactions. It is argued that statistical thermodynamics provides a robust approach to introducing thermodynamics to chemistry and chemical engineering students. Per-Olof Åstrand, Department of Chemistry, NTNU – Norwegian University of Science and Technology, Trondheim, Norway, and Fernando Bresme, Department of Chemistry, Imperial College London, White City Campus, United Kingdom