--%>
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 : PH of an Alkyl Halide Briefly state the

    Briefly state the pH of an Alkyl Halide?

    		•
  • Q : Explain Phase Rule The relation between

    The relation between the number of phases, components and the degrees of freedom is known as the phase rule. One constituent systems: the identification of an area on a P-versus-T with one phase of a component system illustrates the two degrees of freedom that

    		•
  • Q : How to calculate solutions molar

    The contribution of an electrolyte, or an ion electrolyte, is reported as the molar of a conductance. The definition of the molar conductance is based on the following conductivity cell in which the electrodes are 1 m apart and of sufficient area that th

    		•
  • Q : Concentration of urea Help me to go

    Help me to go through this problem. 6.02x 1020 molecules of urea are present in 100 ml of its solution. The concentration of urea solution is: (a) 0.02 M (b) 0.01 M (c) 0.001 M (d) 0.1 M (Avogadro constant, N4= 6.02x 1023mol -1)<

    		•
  • Q : Problem on thermodynamic equilibrium In

    In the manufacture of sulphuric acid by the contact process, S02 is oxidized to SO3 over a vanadium catalyst: The reactor is adiabatic and operates at atmospheric pressure. The gases enter the reactor at 410&d

    		•
  • Q : Basic concept Give me answer of this

    Give me answer of this question. The volume of water to be added to 100cm3 of 0.5 N N H2SO4 to get decinormal concentration is : (a) 400 cm3 (b) 500cm3 (c) 450cm3 (d)100cm3

    		•
  • Q : Solution problem What is the correct

    What is the correct answer. To made a solution of concentration of 0.03 g/ml of AgNO3, what quantity of AgNO3 must be added in 60 ml of solution: (a) 1.8  (b) 0.8  (c) 0.18  (d) None of these

    		•
  • Q : Basicity order order of decreasing

    order of decreasing basicity of urea and its substituents

    		•
  • Q : Problem on mole fraction of glucose

    Provide solution of this question. While 1.80gm glucose dissolve in 90 of H2O , the mole fraction of glucose is: (a) 0.00399 (b) 0.00199 (c) 0.0199 (d) 0.998

    		•
  • Q : Electrochemistry ( electrolysis of

    1. Define Faraday's first law of electrolysis 2. define Faraday's second law of electrolysis

    		•