Central to many issues surrounding reduction in science is the relation between a physical system and its components. In this article we examine how thermodynamic theory relates properties of whole systems to properties of their components. In order to keep the analysis general, we focus our study on universal properties like volume, heat capacity, energy and temperature. In the cases examined we find that scientific explanation requires appeal to properties of components that are spatially as extensive as the whole system. (...) We discuss some implications of our study for the purported paradigmatic reductions of heat and temperature to molecular motion. We conclude that while macro systems reduce ontologically to micro components, epistemologically the reduction of theoretical concepts in general fails. (shrink)

Two different models for chemical bond were developed almost simultaneously after the Schrödinger formulation of quantum theory. These are known as the valence bond (VB) and molecular orbital (MO) theories. Initially chemists preferred the VB theory and ignored the MO theory. Now the VB theory is almost dropped out of currency. The context of discovery and Linus Pauling’s overpowering influence gave the VB theory its initial advantage. The current universal acceptance of the MO theory is due to its ability to (...) provide direct interpretation of many different types of experiments now being pursued. In current research both localized bonds and delocalized charge distributions play important roles and the MO theory has been successful in giving a good account of both. (shrink)

Varieties of chemical and phase equilibria are controlled by the minimum Gibbs energy principle, according to which the Gibbs energy for a system will have the minimum value at any given temperature and pressure. It is understood that the minimum is with respect to all nonequilibrium states at the same temperature and pressure. The abstract relation between Gibbs energy and the equilibrium constant is deduced from fundamental laws of thermodynamics. However, actual use of this relation calls for the Gibbs energy (...) as a function of concentrations of the chemicals. Since thermodynamics is formulated without any reference to materials, how does one get that relation? This article provides the answer, and in the process shows that application of theory to experiments requires several intermediate layers where theory and experiment commingle. (shrink)