--%>
Assignment Help - homework help

Explain gels and its various categories.

Certain sols have the property of setting to a semi-solid, jelly-like form by enclosing the entire amount of liquid within itself when they are present at high concentrations. This process is called gelation and colloidal systems with jelly-like appearance are known as gels. Some common examples of gels are: gelatin, gum Arabic, silicic acid, processed cheese, ferric hydroxide etc.


Gels possess rigid structures which are formed when the particles of dispersed phase get interlocked and create a lose network frame. The particles of dispersion medium are trapped within the loose framework.  The degree of rigidity of structure varies from substance to substance. Thus, gel represents a liquid-solid system, i.e. a liquid immersed in a solid.

When the gels are allowed to stand for long time, they give out small quantity of trapped liquid which accumulates on its surface. This action of gels is known as syneresis or weeping.

Gels are divided into two classes i.e. elastic gels and non-elastic gels. The characteristic differences between the two are tabulated below:

Elastic gels

Non-elastic gels

These gels change to solid mass on dehydration which can be changed back to original form by addition of water followed by warming.

These gels change to solid mass on dehydration which cannot be changed back to original form by addition of water and warming.

The absorb water when placed in it with simultaneous swelling of gel body. This phenomenon is called imbibitions.

These do not imbibe.


Some gels such as silica, gelatin, ferric phosphate, etc, liquefy on mechanical shaking and change to sols losing their semi-solid gel character. The sol on scattering changes back to the gel. This phenomenon is known as thixotropy.

   Related Questions in Chemistry

  • Q : Alkaline medium The amount of KMnO 4

    The amount of KMnO4 required to prepare 100 ml of 0.1N solution in alkaline medium is: (a) 1.58 gm (b) 3.16 gm (c) 0.52 gm (d) 0.31 gmAnswer: (a) In alkaline medium KMnO4 act as ox

    		•
  • Q : Diffusion Molecular View When the

    When the diffusion process is treated as the movement of particles through a solvent the diffusion coefficient can be related to the effective size of diffusing particles and the viscosity of the medium.To see how the experimental coefficients can be treat

    		•
  • Q : Macromolecules what are condensation

    what are condensation polymerization give in with 2 examples

    		•
  • Q : Molarity what is the molarity of the

    what is the molarity of the solution prepared by dissolving 75.5 g of pure KOH in 540 ml of solution

    		•
  • Q : Vapour pressure of benzene Give me

    Give me answer of this question. The vapour pressure of benzene at a certain temperature is 640mm of Hg. A non-volatile and non-electrolyte solid weighing 2.175g is added to 39.08g of benzene. The vapour pressure of the solution is 600,mm of Hg . What is the mo

    		•
  • Q : Concentration of Barium chloride Give

    Give me answer of this question. If 5.0gm of BaCl2 is present in 106 gm solution, the concentration is: (a)1 ppm (b)5 ppm (c)50 ppm (d)1000 ppm

    		•
  • Q : Molar concentration of Iron chloride

    Provide solution of this question. A certain aqueous solution of FeCl3 (formula mass =162) has a density of 1.1g/ml and contains 20.0% Fecl. Molar concentration of this solution is: (a) .028 (b) 0.163 (c) 1.27 (d) 1.47

    		•
  • Q : Analytical chemistry 37% weight of HCl

    37% weight of HCl and density is 1.1g/ml. find molarity of HCl

    		•
  • Q : Vapour pressure of water Give me answer

    Give me answer of this question. 5cm3 of acetone is added to 100cm3 of water, the vapour pressure of water over the solution: (a) It will be equal to the vapour pressure of pure water (b) It will be less than the vapour pressure of pure water

    		•
  • Q : Explain the catalyst definition and

    Catalyst is a substance which accelerates the rate of a chemical reaction without undergoing any change in its chemical composition or mass during the reaction. The phenomenon of increasing the rate of a reaction with the help of a catalyst is known as catalysis.

    		•