Week 4 States of matter. The gaseous state. State functions. Kinetic theory of gases. Maxwell’s distribution of molecular speed. Gas laws: Boyle’s law, Charles’s law, Avogadro’s law. The ideal gas law. Molar gas constant (R ). Real gases. The liquid state. Changes of state. Dependence of phase changes on pressure and temperature: phase diagrams. Intermolecular forces. Association of molecules. Properties of liquids. The solid state. Types of solids. Properties of crystalline solids. The crystalline lattice and crystal systems. Types of crystalline lattice. Sublimation and lyophilization. Homogenous and heterogeneous systems. Homogenous systems: mixtures of gases, solutions and alloys. Microheterogeneous systems: colloidal state. Colloidal size. Tyndall-effect. Properties of colloids. Types of colloids. Preparation of colloids. Major classes: hydrophobic and hydrophilic, dispersed and associated colloids (micelles). Macromolecular colloids.

Postulates of Kinetic Theory Postulate 1 Gases are composed of molecules whose size is negligible compared with the average distance between them. Postulate 2 Molecules move randomly in straight lines in all dirctions and at various speeds. Postulate 3 The forces of attraction or repulsion between two molecules (intermolecular forces) in a gas are very weak or negligible, except when they collide Postulate 4 When molecules collide with one another, the collisions are elastic. Graham’s law of effusion in terms of molecular weight: the rate of effusion of gas molecules from a particular hole is inversely proportional to the square root of the molecular weight of the gas at constant temperature and pressure.

A colloid is a dispersion of particles of one substance (the dispersed phase) throughout another substance or solution (the continous phase). Fog is an example of a colloid: it consists of very small water droplets (dispersed phase) in air (continuous phase). A colloid differs froma true solution in that the dispersed particles are larger than normal molecules, though they are too small to be seen with a microscope. The particles range from about 1 x 103 pm to about 2 x 105 pm in size.