STRUCTURE OF LIQUIDS AND SOLUTIONS

As we focus our attention on the liquid state and on solutions, I shall make a few comments on the relation of the liquid state to the gaseous and solid states of matter. The space in a system constituting a gas is sparsely occupied. Owing to their thermal energy, the molecules of a gas are in continual motion and collide occasionally with one another and with the walls of their container but rebound without loss of energy to the system. Because of the near-independence of the particles of a gas, a gas can expand to an unlimited volume. Thus, the distinctive feature of the gaseous state is that its particles (atoms or molecules) are sub-stantially independent of each other except for occasional collisions. A primary property of a liquid is that it occupies a certain amount of space; it has a definite density at a given temperature and pressure. The particles of a liquid are close enough to be in contact with one another. In contrast to the gas, the attraction of one molecule to its immediate neighbor is high and, when a liquid is poured, it maintains a constant volume. Furthermore, the molecules in a liquid do not have particular partners as they do in solids, and this irregularit