Question

What is an emulsion? How are emulsions classified? Give an example?

Answer 1

Hint: You might’ve heard that milk is an emulsion. Emulsion is a particular type of colloidal solution with a dispersed phase and dispersion medium. The stability of an emulsion depends on a substance known as an ‘emulsifier’, which may either be naturally present or artificially added.

Complete step by step answer:
Emulsion is defined as “a colloidal system in which one liquid is dispersed in another liquid immiscible liquid”. The phases are often termed as a dispersion medium and dispersed phase, that are separated by a boundary layer known as ‘interface’.
The dispersed phase is distributed in a dispersion medium. They are stabilized by an emulsifier.
On the basis of the dispersion medium and dispersed phase, we classify emulsions in two types –
1. Oil-in-water
- In this type of emulsion, the dispersed phase is oil whereas the dispersion medium is water.

2. Water-in-oil
- In this type of emulsion, the dispersed phase is water whereas the dispersion medium is oil.

We use many emulsions in our daily lives. For example –
> Oil-in-water emulsion
- Milk
- Mayonnaise

> Water-in-oil emulsion
- Butter
- Margarine

Additional Information:
An emulsifier (also known as emulgent) is a substance which possesses the ability to stabilize an emulsion. Emulsifiers do this by increasing the kinetic stability of a mixture.

Note: There are many tests that are used to identify the type of emulsions. The tests are as given below–
1. Dye test
- This test is performed by adding a water-soluble dye to the emulsion. The dye turns the water red, whereas the oil remains colourless. Therefore, in water-in-oil emulsion, the dispersion medium appears colourless, whereas the dispersed phase is red.

2. Dilution test
- Adding a diluent same as the dispersed phase will not destabilize the emulsion, but adding a diluent different from the dispersed phase will destabilize the emulsion. Therefore, water-in-oil emulsion can be diluted with oil, it would still be stable, but it will destabilize on the addition of water.

3. Conductivity test
- Oil-in-water emulsion conducts electricity, whereas, water-in-oil emulsion does not.