Class 9 Science
Suspension is the heterogeneous mixture of two or more substances. In suspension, particles are suspended throughout in bulk and can be seen by naked eyes. In suspensions, particles of solute do not dissolve rather are suspended. Particles of suspension are large enough to scatter rays of light and path of ray is visible through a suspension.
Example of suspension: mixture of chalk and water, muddy water, mixture of flour and water, mixture of dust particles and air, fog, milk of magnesia, etc.
Colloidal solution is a heterogeneous mixture of two or more substances. Colloidal solutions appear homogenous because of relatively small size of particles in comparison with suspension. Particles of colloidal solution are called colloid. Colloids are dispersed throughout the solvent. Particles of colloidal solution are not visible through naked eye but scatter the ray of light, i.e. show Tyndall effect. Colloids cannot be separated by filtration but can be separated using centrifugation. Milk, ink, blood, solution of soap or detergent, etc. are some common examples of colloidal solution.
There are two components of a colloidal solution – dispersed phase and dispersing medium. The solute like component of colloidal solution is called dispersed phase and solvent like component is called dispersing medium. The dispersed phase and dispersing medium may be solid, liquid or gas.
Colloids are classified on the basis of their components, i.e. dispersed phase and dispersing medium.
Aerosol: When particles of solid or liquid dispersed in gaseous medium, the mixture is known as Aerosol. For example – cloud, smog, smoke etc.
Aerosol is of two types – Liquid Aerosol and Solid Aerosol.
Foam: Mixtures are called foam when liquid is present as dispersing medium and gas is dispersed medium. For example – shaving cream, soap bubbles, etc.
Emulsion: Colloidal solution is called emulsion, when dispersing medium and dispersed phase both are liquid. For example – milk, butter, face cream, etc.
Sol: Colloidal solution is called sol when liquid is dispersing medium and solid is dispersed phase. For example – blood, ink, paint, etc.
Solid foam: Solid foam is formed by the mixing of solid as dispersing medium and gas as dispersed phase. For example – Styrofoam, pumice stone, bread, etc.
Gel: Gel is formed by the mixing of solid as dispersing medium and liquid as dispersed phase. For example – gelatin, jelly, hair gel, etc.
Solid sol: Solid sol is formed by the mixing of solid as dispersing medium and solid as dispersed phase. For example - coloured gem stone, cranberry glass, etc.
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