Question

An example of a colloid which is an emulsion is:
A. Whipped cream
B. Mayonnaise
C. Fog
D. Gelatin

Answer 1

Hint: A colloid is defined as a substance that has larger size than an atom, but they are very small through naked eye. They exist as dispersion of one substance in another. For example, smog particles in the air. It consists of dispersion phase and dispersion medium that are immiscible to each other.

Complete step by step answer:
Colloids are classified on the basis of the nature of interaction between dispersion medium and dispersed phase. The colloids are classified into two types:
Hydrophilic colloids: Hydrophilic colloids are the colloids that are attracted to water.
Hydrophobic colloids: Hydrophobic colloids are the colloids that are repelled by the water. They are just opposite as the hydrophilic colloids.
Colloidal particles electrostatic interaction in which these particles often attract or repel each other due to the presence of electrical charge. The factors that affect the electrostatic interaction are charge of both the continuous and dispersed phase, mobility of the phases.
Emulsion is defined as a type of a colloid in which two immiscible liquids are combined together, where one liquid contains the dispersion of another liquid.
Now let us discuss the options given in this question.
Whipped cream is an example of sol where the dispersion medium is liquid and dispersion phase is gas. Therefore, this option is incorrect.
Mayonnaise is an example of emulsion in which two immiscible liquids, that are, oil and vinegar do not mix and separate into layers. Egg yolk is used to stabilize this mixture. It has the ability to interact with non – polar oil and polar vinegar. It is also known as an emulsifying agent that stabilizes an immiscible mixture and does not let them separate. Therefore, this option is correct.
Fog is an example aerosol in which liquid is the dispersed phase and gas is the dispersed medium. Therefore, this option is incorrect.
Gelatin shows the behavior of both sol and gel. When temperature is increased, gelatin behaves as a hydrosol, whereas when temperature is decreased, it is converted into gel. Therefore, this option is incorrect.

So, the correct answer is Option B .

Note: In emulsions both the dispersed phase and dispersion medium are liquids.
Emulsions are very unstable colloids and therefore require stabilizing agents known as emulsifiers .
Dispersed phase is defined as the phase that contains finely divided particles, known as colloidal particles.
Dispersion medium is the medium in which colloidal particles are distributed.