Dispersed Phase and Dispersion Medium - Definition, Examples and FAQs
Have you ever wondered why milk appears white, why paint remains mixed for a long time? How do we classify such mixtures into colloids, suspensions, and solutions? You can find the answer to these questions by studying the dispersed phase and the dispersion medium. A substance that is distributed throughout another substance is the dispersed phase, while the dispersion medium is the continuous phase in which dispersion particles are suspended.
This Story also Contains
- Dispersed Phase And Dispersion Medium
- Colloids
- Multimolecular Colloids
- Macromolecular Colloids
- Associated Colloids
- Some Solved Examples
Two or more substances are homogeneously combined to form a solution. Those substances that get dissolved are referred to as solutes and those substances in which the solute is dissolved are solvents. For example, salt (solute) dissolved in water (solvent). The concentration of the solution is determined on the basis of the amount of solute dissolved in the solvent. Based on the amount of solute that is dissolved in the solvent, solutions can be further classified as saturated solutions, Unsaturated Solutions, and supersaturated solutions.
Dispersed Phase And Dispersion Medium
The substance present in the form of fine particles in a colloid or heterogeneous mixture is called the dispersed phase. And the dispersion medium is the continuous phase in which these particles are distributed. Think of the dispersed phase as the solute and the dispersion medium as the solvent in a solution. The dispersed phase is particles, and the dispersed medium is called the continuous phase. Both combined and formed the colloids.
We have classified colloids on the basis of the dispersed phase and the dispersion medium, such as:
| Colloidal System | Dispersed Phase | Dispersion Medium | Type |
| Milk | Fat globules | Water | Emulsion |
| Fog | Water droplets | Air | Aerosol |
| Butter | Water | Fat | Emulsion (gel) |
| Smoke | Carbon particles | Air | Aerosol |
| Paint | Pigment particles | Water/Oi | Sol |
Colloids
Between the two extremes of suspensions and solutions, we come across a large group of systems called colloidal dispersions or simply colloids. A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called the dispersion medium.
The essential difference between a solution and a colloid is that of particle size. While in a solution, the constituent particles are ions or small molecules, in a colloid, the dispersed phase may consist of particles of a single macromolecule (such as a protein or synthetic polymer) or an aggregate of many atoms, ions, or molecules. Colloidal particles are larger than simple molecules but small enough to remain suspended. Their range of diameters is between 1 and 1000 nm(10–9 to 10–6 m). Colloidal particles have an enormous surface area per unit mass as a result of their small size.
On the basis of the types of particles in the dispersed phase, colloids can be classified into the following types:
- Multimolecular colloids
- Macromolecular colloids
- Associated colloids
Multimolecular Colloids
Multimolecular colloids are colloidal systems in which individual atoms or small molecules of a substance aggregate to form particles of colloidal size (1–1000 nm). These aggregates act as the dispersed phase, while the surrounding liquid or gas acts as the dispersion medium. The particles are held together by Van der Waals forces or weak chemical bonds.
Macromolecular Colloids
Macromolecular colloids are colloidal systems in which are composed of molecules with very large molecular weight, highly stable due to their large size and strong interaction with the medium. In macromolecular colloids, the dispersed phase consists of large molecules (macromolecules) whose sizes are in the colloidal range (1–1000 nm).
Associated Colloids
Associated colloids are substances that behave as normal electrolytes at low concentrations but form colloidal-sized aggregates (micelles) at higher concentrations. These aggregates are known as micelles. Such colloids show properties of both true solutions and colloids.
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Some Solved Examples
Question.1 Which of the following statements is true about a colloidal system?
a) Only one phase is present
b) Both dispersed phase and dispersion medium are present
c) No continuous phase exists
d) Colloids are always solids
Solution:
Both dispersed phase and dispersion medium are present
A colloid always consists of two components—the dispersed phase (particles) and the dispersion medium (continuous phase).
Hence, the correct option is (b)
Question.2 In milk, the dispersed phase and dispersion medium are respectively:
a) Water and fat
b) Fat and water
c) Protein and water
d) Water and protein
Solution:
Milk is an emulsion where fat globules are the dispersed phase and water is the dispersion medium.
Hence, the correct option is (b) Fat and water
Question.3 Which of the following pairs is correctly matched for smoke?
a) Dispersed phase – Air, Dispersion medium – Carbon particles
b) Dispersed phase – Carbon particles, Dispersion medium – Air
c) Dispersed phase – Water, Dispersion medium – Air
d) Dispersed phase – Air, Dispersion medium – Water
Solution:
Smoke is a solid in gas colloid, where carbon particles are dispersed in air.
Hence, the correct option is (b) Dispersed phase – Carbon particles, Dispersion medium – Air
Practice More Questions With The Link Given Below:
| Colloids Practice questions and MCQs |
| Multimolecular and Macromolecular Colloids Practice Questions and MCQs |
| Associated Colloids Practice questions and MCQs |
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Frequently Asked Questions (FAQs)
The dispersion medium, also known as the continuous phase, in which the dispersed phase is distributed. It can be a solid, liquid, or gas. In a colloidal mixture like milk, for example, the dispersion medium is water, and the dispersed phase consists of fat globules.
Common examples are:
- Fog in which the dispersed phase is water droplets, the dispersion medium is air
- Smoke in which the dispersed phase is solid soot particles, and the dispersion medium is air.
- Milk in which the dispersed phase is fat globules, the dispersion medium is water.
Common examples include rock candy, where sugar is dissolved in hot water and then slowly crystallizes as the solution cools. Another example is carbonated beverages, which can contain dissolved carbon dioxide under pressure, creating a supersaturated solution that releases gas bubbles when opened.
To create a supersaturated solution, you typically heat a solvent and dissolve solute into it until no more solute can dissolve. Once the solution is saturated and no solid remains, you slowly cool the solution. If cooled carefully without disturbing it, the solution can remain supersaturated.
A supersaturated solution is a solution that contains more solute than what can normally be dissolved in a given amount of solvent at a specific temperature. This state is achieved by dissolving more solute than usual, often at elevated temperatures, and then allowing the solution to cool without any crystallization occurring.
A colloid is a substance wherein minute, microscopically dispersed insoluble debris of a substance is suspended in some other substance. The length of colloidal debris varies from 1-1000. A solution exists in a single-phase only, and no visible interface exists. Whereas in a colloid, unique phases, particularly the dispersed section and dispersion medium, exist. An interface among them may be observed.
The normal range of particles in a colloidal solution is 1- 1000 nm.
Dust is an aerosol type of colloid where a solid is suspended in a gas.