Analysis of trends in phase change enthalpy, entropy and temperature for alkanes, alcohols and fatty acids

Abstract

In this work, relationships for enthalpy changes and entropy changes associated with phase transitions, specifically for alkanes, alcohols, and fatty acids, were investigated. For each homologous series, linear correlations were observed between: enthalpy and entropy change, enthalpy change and number of carbon atoms, and entropy change and number of carbon atoms. The observed correlations are explained in terms of the molecular structure, especially the functional group. For a given number of carbon atoms, common behavior regarding enthalpy change (and entropy change) was also observed if the functional group changed, for alcohols, even for multiple functional groups, and for alkanes, even if branched. The investigations thus show general, common phase change behavior, and significantly improve the empirical description and theoretical understanding.

Keywords

• Enthalpy change
• Temperature
• Entropy change
• Phase change
• Organic materials
• PCM