Suspension and Colloids
- Characteristics of suspension
- Characteristics of colloidal solution
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.
General Characteristics of Suspension:
- Suspensions are heterogeneous mixture of two or more substances.
- Particles of solute do not dissolve in solvent rather they remain suspended in bulk throughout.
- The size of particles of suspension is large enough to be visible from naked eyes. They are greater than 1 nanometre (`10^(-9)` metre).
- Suspension shows Tyndall effect because of their large size of particles.
- When suspension is left for some time, particles get settled in bottom.
- Therefore, suspension is not stable.
- The particles of suspension can be separated through the process of filtration.
- Suspension does not scatter light when particles are settled because in this case suspension breaks.
- Milk of magnesia, fog, mixture of chalk and water, etc. are some examples of suspension.
Colloidal Solution
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.
General Characteristics of Colloidal Solution:
- Colloidal solutions are heterogeneous mixture of two or more substances.
- Colloidal solutions appear homogeneous.
- The size of colloids is between the size of particles of solution and suspension, i.e. between 1 nanometer to 1000 nanometer.
- Colloids cannot be seen even using optical microscope.
- Colloids show Tyndall effect, i.e. they scatter the ray of visible light.
- Colloidal solutions may be opaque, translucent or of light colour.
- Colloids cannot be separated by filtration. But they can be separated by centrifugation. For example fat can be separated by centrifugation from milk.
- Colloidal solutions are stable since colloids cannot settle down when left undisturbed.
Components 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.
Types of Colloidal Solution:
Colloids are classified on the basis of their components, i.e. dispersed phase and dispersing medium.
- Liquid Aerosol
- Solid Aerosol
- Foam
- Emulsion
- Sol
- Solid foam
- Gel
- Solid sol
Gas as dispersing medium:
Aerosol: When particles of solid or liquid are 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.
- Liquid Aerosol: When liquid particles are dispersed phase and gas is dispersing phase, the mixture is known as Liquid Aerosol. For example – fog, mist, hair spray, etc.
- Solid Aerosol: When solid particles are dispersed phase and gas is dispersing phase, the mixture is known as Solid Aerosol. For example, smoke, air particulates, automobile exhaust, etc.
Liquid as dispersing medium:
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 as dispersing medium
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.
Quiz
See Answer
1: (a) Chalk in water, 2: (d) All of these, 3: (b) Suspension, 4: (c) Milk of magnesia, 5: (d) Aerosol, 6: (b) Foam, 7: (c) Emulsion, 8: (d) Sol, 9: (b) Dispersed phase is liquid and dispersing medium is gas, 10: (a) Both dispersed phase and dispersing medium are liquid