Most of the observable characteristics of system of matter with which we are familiar represent bulk properties of matter, i.e., the properties associated with a collection of a large number of atoms, ions or molecules. For example, an individual molecule of a liquid does not boil but the bulk boils. Collection of water molecules has wetting properties; individual molecules do not wet. However, properties of single particle have significant effect on the properties of the bulk matter. Therefore, before going into some properties of the bulk matter you will study the structure of matter to the molecular or single particle level.

You may remember that under normal conditions substances exist mainly in one of the three major states of matter: solid state, liquid state, and gaseous state of matter. The existence of matter in any of these states depends on the balance between the attractive intermolecular forces and dispersive forces due to thermal energy in the system. In this unit, you will learn about observable properties of matter; dependence of observable properties on the microscopic (atomic/molecular) properties; about attractive and repulsive intermolecular force and forces due to thermal energies, on the basis of the kinetic theory of matter. And you will also look at some of the physical properties of the liquids such as surface tension and viscosity and their dependence on intermolecular forces. You will also learn about elastic and plastic behaviors of matter on the basis of Hooke’s law.