Aggregations of Atoms—The Fluid States

Abstract

In general, the engineer does not need to consider atoms as individuals, but is concerned with the properties or behaviour of assemblages of atoms in one or more of the three states of aggregation: gas, liquid, and solid. In gases, the spacing of the atoms or molecules is large (except at very high pressures), but in liquids and solids each atom is in close proximity to its neighbours. The state of aggregation in which a particular group of atoms or molecules exists depends on the nature of the attractive forces present and may vary with changes in temperature and pressure. Under any particular set of conditions, the state or states will be such that the energy of the system is a minimum.