Which of the following colloidal system represents a gel?

Liquid in solid

The correct answer is option 3. Liquid in solid.

A colloidal system representing a gel can indeed be "liquid in solid."

In this type of colloidal system, a liquid phase is dispersed within a solid continuous phase. The solid phase forms a three-dimensional network or matrix structure, often composed of polymers or other solid materials. Within this solid matrix, the liquid phase is trapped or immobilized, giving the material a gel-like consistency.

The formation of gels typically involves the cross-linking or bonding of polymer chains within the solid phase. These cross-links create a network that holds the liquid phase in place. The amount and type of cross-linking can influence the properties of the gel, such as its strength, elasticity, and ability to retain water.

Hydrogels are a common example of gels where water or another liquid is dispersed within a solid polymer network. Hydrogels are used in various biomedical and industrial applications due to their ability to absorb and retain large amounts of water while maintaining their structural integrity.

Overall, in a colloidal system where the liquid phase is dispersed within a solid continuous phase, the resulting material exhibits gel-like properties, making it a representative example of a gel colloidal system.