The three primary states of matter are the result of a competition between thermal energy and intermolecular forces. In this book we show that many of the bulk properties of a given substance in its gaseous, liquid and solid state may be correlated in terms of intermolecular forces thus emphasizing the fact that the three states are linked by a common property. Simple models are introduced and the mathematics is generally straightforward and unsophisticated.

Chapter 1 is a simple account of the nature of atoms and molecules and the forces between them, and includes a rather more detailed explanation of van der Waals forces. The second chapter deals with temperature and the concept of heat. These are the introductory chapters.

The next three chapters describe the properties of gases. This is a well-worn area where the molecular approach has long been used to describe the bulk behaviour. Chapter 3 gives the simple kinetic theory of ideal gases, while Chapter 4 deals with a more sophisticated treatment which includes a simplified approach to the Boltzmann distribution, and a discussion of the equipartition of energy. Chapter 5 deals with imperfect gases where perfect gas behaviour is modifled to allow for the finite size of the molecules and for the forces between them.

We turn at once from gases to solids. In gases the molecules are virtually free, in solids they are bound to particular sites and their main thermal exercise consists in vibrating about their equilibrium positions.