What Is A Colloid?
A colloid is a homogenous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. A common method of classifying colloids is based on the phase of the dispersed substance and what phase it is dispersed in. Colloids include: gels, sols, aerosols and emulsions. In colloids particles cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
Colloids are generally classified into two systems, reversible and irreversible. An irreversible system is one in which the products of a reaction are so stable or are removed so effectively from the system that its original components cannot be reproduced whereas in reversible system, the products of a physical or chemical reaction may be induced to interact so as to reproduce the original components.
Tyndall Effect is usually used to determine whether a mixture is colloidal or not. Tyndall Effect is the scattering of visible light by colloidal particles. In this method, when light is passed through a colloidal solution, the substance in the dispersed phases scatters the light in all directions, making it readily seen.
Also a mixture can be passed through s semi-permeable membrane to determine whether it is colloidal or not. In this process, larger dispersed particles in a colloid would be unable to pass through the membrane, while the surrounding liquid molecules can.
What Is A Suspension?
A suspension is a heterogeneous mixture in which some of the particles settle out of the mixture upon standing. The particles in a suspension are usually larger than those of a solution; therefore gravity is able to pull them down out of the dispersion medium (water). Examples of Suspensions include:
- Muddy water-composed of mud particles in water.
- Paints
- Sand in water
- Fine soot or dust in the air
- Droplets of oil in air
- Harmatan haze-composed of tiny solid particles such as dust particles, decaying organic matter in air etc.
Suspensions are considered heterogeneous because the different substances in the mixture will not remain uniformly distributed if they are not actively being mixed. When Tyndall Effect is applied in suspension, suspension may scatter light, but if the number of suspended particles is sufficiently large, the suspension may simply be opaque and the light scattering will not occur. Suspension can be separated by filtration and by a semi permeable membrane.
Key Differences
- A suspension is a heterogeneous mixture of two substances in which one is dispersed into the other; suspensions involve particles larger than those found in solution, typically over 1000 nm. On the other hand, a colloid solution is a heterogeneous mixture in which particle size of substance is intermediate of true solution and suspension i.e between 1-1000 nm.
- In a suspension, particles can be clearly seen by naked eye whereas particles of colloid cannot be seen by the naked eye but can be seen under a light microscope.
- Colloids are translucent in nature whereas suspension is opaque in nature.
- In suspension, particles do undergo sedimentation while in colloids particles do not undergo sedimentation.
- Suspension particles do not pass through filter paper and parchment paper whereas colloid particles can pass through a filter paper but not through parchment paper.
- Colloids show Tyndall effect whereas suspension may or may not show Tyndall effect.
- The phase of separation of a suspension can be seen to happen whereas the phase of separation of colloids is either very slow or might not happen.
- Suspensions are used in the production of medication and milk of magnesia while colloids are used in the paint industry, food industry, perfume industry and other related industries.
- Examples of suspension are soil dissolved in water, soot in air, oil and water whereas examples of colloidal solution include starch dissolved in water, milk, shampoo, gemstones, foam and rubber.
Read Further: Difference Between Sol And Gel With Examples
Colloid Vs. Suspension In Tabular Form
| BASIS OF COMPARISON | COLLOID | SUSPENSION |
| Description | A colloid solution is a heterogeneous mixture in which particle size of substance is intermediate of true solution and suspension i.e between 1-1000 nm. | A suspension is a heterogeneous mixture of two substances in which one is dispersed into the other; suspensions involve particles larger than those found in solution, typically over 1000 nm. |
| Particle Suspension | Particles of colloid cannot be seen by the naked eye but can be seen under a light microscope. | In a suspension, particles can be clearly seen by naked eye. |
| Nature | Colloids are translucent in nature. | Suspension is opaque in nature. |
| Sedimentation | Colloids particles do not undergo sedimentation. | In suspension, particles do undergo sedimentation. |
| Passage Through Parchment and Filter paper. | Colloid particles can pass through a filter paper but not through parchment paper. | Suspension particles do not pass through filter paper and parchment paper. |
| Tyndall Effect | Colloids show Tyndall effect. | Suspension may or may not show Tyndall effect. |
| Phase Of Separation | The phase of separation of colloids is either very slow or might not happen. | The phase of separation of a suspension can be seen to happen. |
| Application | Colloids are used in the paint industry, food industry, perfume industry and other related industries. | Suspensions are used in the production of medication and milk of magnesia. |
| Examples | Examples of colloidal solution include starch dissolved in water, milk, shampoo, gemstones, foam and rubber. | Examples of suspension are soil dissolved in water, soot in air, oil and water. |
Also Read: Difference Between Homogeneous And Heterogeneous Mixture