Gels : A gel is jelly-like colloidal system in which a liquid is dispersed in a solid medium. The process of gel formation is known as gelation.
Gel represents a liquid-solid system i.e., a liquid is dispersed in a solid. Gelation may be considered as partial coagulation of a sol.
The coagulating solution particles first aggregate to form a long thread-like chain. These chains are then interlocked to form a solid framework. The liquid dispersion medium is caged in the cavities of this structure. The resulting semi-solid porous mass has gel structure.
Classification of Gel :-
1) Elastic Gels :These are those gels which posses the property of elasticity. They change their shape on applying force and return to original shape when the force is withdrawn.
exam:- Gelatin, starch and soaps are substance which forms elastic gels.
2) Non-Elastic Gels :These are those gels which are rigid.They are irreversible. When hydrated becomes glassy or changes into a powder which on addition of water and followed by warming does not change back into the original gel.
exam:- Silica gel.
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