Introduction

Physical chemistry is concerned with the structures of chemical compounds, the mechanisms by which these compounds react and the energy changes that accompany the reactions between the chemical species. Studies in these fundamental aspects of the subject are based largely upon experimental measurements, but theoretical and computer-simulation techniques provide powerful additional methods of investigation. Notwithstanding the subject has, for convenience here, been subdivided, the sections are inevitably linked, so that the order in which they are treated is simply a matter of preference.

All chapters are provided with sets of problems, for which detailed solutions are available on the Internet (see Preface), that have been designed to enhance the reader's appreciation of the subject matter. The reader is encouraged to attempt these problems, and the material described in Appendix 1 should be of assistance in this aspect of the study.

Structure

The term structure embraces a wide range of properties, among which we may include the stereochemistry of a molecule, the lengths of bonds between its atoms, the angles between pairs of bonds, the vibrations of atoms and groups of atoms, the distribution of electron density, the arrangement of molecules in the condensed state and the contact, or nonbonded, distances between species.

In the water molecule H2O, for example, each hydrogen atom is linked to the oxygen atom by a bond that is mainly covalent, with O–H bond lengths of 0.096 nm and an H–O–H bond angle of 104.4˚; the distance between the two hydrogen atoms, the intramolecular proton separation, is 0.152 nm.