Solutions and Colloids

It is observed that solutions are of paramount importance to those vital processes which sustain life itself, as well as to a great multitude of other phenomena involving chemical transformations. In this present chapter, we shall direct our consideration towards the essential nature of solutions; furthermore, we shall examine those agencies which determine whether a solution may be successfully formed, and what particular properties it might thereafter possess. In addition, we propose to discuss colloids—those systems which, while bearing a resemblance to true solutions, consist of dispersions of particles somewhat larger in magnitude than the ordinary molecule or ion.

An alchemist’s experiment in an ancient laboratory illustrates the Tyndall effect, where a beam of light becomes visible due to scattering by newly formed colloidal particles.

The Dissolution Process

By the conclusion of this section, the pupil will be expected to have attained the following objectives: To describe the fundamental properties of solutions and the manner in which they are formed. To predict, on the basis of molecular properties, whether a given mixture will form a solution. To explain why the formation of certain solutions is accompanied by the evolution or absorption of heat.

Electrolytes

By the conclusion of this module, the pupil will be expected to have attained the following objectives: To define the term electrolyte and to give representative examples. To distinguish between the physical and chemical changes that accompany the dissolution of ionic and covalent electrolytes. To relate the strength of an electrolyte to the attractive forces operating between solute and solvent.

Solubility

By the conclusion of this module, the pupil will be expected to have achieved the following aims: To describe the effects of temperature and pressure upon solubility. To state Henry’s law and to apply it in calculations concerning the solubility of a gas in a liquid. To explain the various degrees of solubility possible in liquid–liquid solutions.

Colligative Properties

By the conclusion of this section, the pupil will be expected to have attained the following objectives: To express the concentrations of the components of a solution by means of mole fraction and molality. To describe the influence of solute concentration upon various properties of solutions, including vapour pressure, boiling point, freezing point, and osmotic pressure. To carry out calculations employing the mathematical relations that govern these colligative effects. To describe the process of distillation and to indicate its practical applications. To explain the process of osmosis, and to describe its application both in industry and in nature.

Colloids

By the conclusion of this section, the pupil will be expected to have achieved the following aims: To describe the composition and characteristic properties of colloidal dispersions. To enumerate and explain several technological applications of colloids.