Question

Define the following with a suitable example of each:
(A) Coagulation
(B) Multimolecular colloid
(C) Gel

Answer 1

All the above given topics are related to colloids.
- Colloids are the solutions having the size of solute particles in between the range of true solution and suspension.
- Gel is a classification of colloids based on the physical state of dispersion medium and dispersed phase.
- Coagulation is the phenomenon in which the particles in colloids aggregates and multimolecular colloids are colloids classified on the basis of the properties of the sol particle.

Complete Solution :
So in the question we have to define the three terms related to colloids.
In the smaller classes we have studied about colloids and its classifications based on different parameters. From the basic ideas, now let’s define the given terms and explain with an example.
-Coagulation:
So the coagulation is a property of colloids in which the particles clumping together when their oppositely charged particles aggregate together and then gravity causes them to settle down at the bottom.
- Generally solutions of metals of sulphides are lyophobic solutions i.e. they cannot be simply mixed with dispersion medium; we have to use special techniques to make the solutions of the metal sulphides. And these solutions contain charges and when the oppositely charged particles attract and aggregate with the aid of gravity and settle down and form the colloidal solution. This process of precipitation or aggregation of the particles in the dispersion medium is called the coagulation process.
For example, milk proteins coagulate to thicken the mixture that forms yogurt.
- Coagulation is the phenomenon by which blood changes from a liquid to a gel, which results in a blood clot. The mechanism of coagulation mainly involves the steps like activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin.
- Coagulation defects may cause severe medical conditions like thrombosis or haemorrhage, and occasionally both depending upon the nature of the defect.

-Multimolecular colloids:
So multimolecular colloids are the solution, when a large number of atoms or smaller molecules which possess a diameter of about less than 1nanometer are dissolved in a dispersion medium, the particles combine to form a species whose size is in the range of colloidal size. And these species formed are known as the multimolecular colloids. They are usually lyophobic in nature and are unstable.
For example: The solution of sulphur or say sulphur sol contains thousands of ${{S}_{8}}$ particles in them.

-Gel:
Gel is the soft solid or semi-solid form of colloidal solution. A gel is a colloidal system in which the dispersion medium is solid and liquid acts as the dispersion phase .Gel is formed by the interlocking of the solid dispersion medium in which the liquid is entrapped, the weight of the gel is due to this liquid phase. Hence we can say that the gels are colloids in which the liquid medium has become viscous enough to behave more or less as a solid.
For example: jelly.
Gels are mainly of two types –elastic and non-elastic gels

Note: Remember that colloids include gels, sols and emulsions. As these particles do not settle down easily, hence cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
- The liquid state of colloidal solutions is generally called the sol which is different from that of gel.