Question

Which of the following examples is/are oil-in-water-type emulsion?
(A) Ink
(B) Detergent
(C) Soap
(D) Milk

Answer 1

Hint: An emulsion is a mixture of two or more non-homogenous type of liquids. One of these is called as the dispersed phase while the other is dispersion medium.
Complete step by step answer: An emulsion is defined as a colloidal mixture of two or more non-homogenous type of liquids, one out of which is dispersed phase and the other is dispersion medium. Based on the properties of dispersed phase and dispersion medium, emulsions are classified into two major types –
1. Oil in water (O/W) type of emulsion –

Oil is the dispersed phase and water is the dispersion medium. For e.g. – Milk.

2. Water in oil (W/O) type of emulsion –

Water is the dispersed phase and oil is the dispersion medium. For e.g. – butter.

So, from the given options, Milk is an example of oil-in-water type of emulsion.
In milk fat globules act as dispersed phase and water acts as a dispersion medium.
Hence, option D is correct answer.
Additional information: There are certain other differences in Oil-in-water and water-in-oil type of emulsions. These are as follows-

Oil-in-water	Water-in-oil
Water is the dispersion medium and oil is the dispersed phase.	Oil is the dispersion medium and water is the dispersed phase.
Continuous phase is water.	Continuous phase is oil.
Non-greasy and can be easily removed from skin.	Greasy and cannot be easily removed from skin.
Widely used to provide s cooling effect externally.	Widely used to maintain moisture content.

Note: Usually emulsions are written in ‘dispersed phase-in-dispersion medium’ format i.e. the first written substance will always be dispersed phase and latter will always be dispersion medium.