Question

a) Define the following terms
i)colloid. [1 Marks]
ii)Dispersion medium and dispersed phase. [1 Marks]

b)Identify the dispersed phase and dispersing medium in the following colloids. [1 Mark]
i) Fog
ii) Cheese

c)Define tyndall effect. [1 Mark]

Answer 1

a) Colloids (also known as colloidal solutions or colloidal systems) are mixtures in which microscopically dispersed insoluble particles of one substance are suspended in another substance. The size of the suspended particles in a colloid can range from 1 to 1000 nanometres. [1 Mark]

In colloids, the substance that is dispersed is referred to as the dispersed phase whereas the substance through which it is dispersed is called the dispersion medium. [1 Mark]

b)
(1) Fog—liquid dispersed in gas [ 0.5 Mark]
(2) Cheese—liquid dispersed in solid [0.5 Mark]

c) Tyndall effect is the process of scattering of light in colloidal or very fine suspended solutions. In this effect, the light beam is scattered by the particles suspended in a colloidal solution.
This can be used to determine whether a mixture is a true solution or a colloid. [1 Mark]