--%>
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 : Organic structure of cetearyl alcohol

    Show the organic structure of cetearyl alcohol and state what the organic family is? Briefly state it.

    		•
  • Q : Colligative property related question

    Select the right answer of the question. Which of the following is not a colligative property : (a) Osmotic pressure (b) Elevation in B.P (c) Vapour pressure (d) Depression in freezing point

    		•
  • Q : Quantum Mechanical Operators The

    The quantum mechanical methods, illustrated previously by the Schrödinger equation, are extended by the use of operators. Or, w

    		•
  • Q : Basicity order order of decreasing

    order of decreasing basicity of urea and its substituents

    		•
  • Q : What is Elevation in boiling point? The

    The boiling of a liquid may be defused by the temperature at which its vapour pressure which is equal to atmospheric pressure. The effect of addition in a non-volatile solute on the boiling point shown and its solution containing non-volatile solute with tempe

    		•
  • Q : Electrons present in a benzene How

    How many electrons are present in a benzene?

    		•
  • Q : Number of moles present in water

    Provide solution of this question. How many moles of water are present in 180 of water: (a)1 mole (b)18 mole (c)10 mole (d)100 mole

    		•
  • Q : Explain the process of adsorption of

    The extent of adsorption of a gas on a solid adsorbent is affected by the following factors: 1. Nature of the gas Since physical adsorption is non-specific in nature, every gas will get adsorbed on the

    		•
  • Q : Molecular weight of solute Select right

    Select right answer of the question. A dry air is passed through the solution, containing the 10 gm of solute and 90 gm of water and then it pass through pure water. There is the depression in weight of solution wt by 2.5 gm and in weight of pure solvent by 0.05 gm. C

    		•
  • Q : Vapour pressure of the pure hydrocarbons

    Give me answer of this question. A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20°C are 440 mmHg for pentane and 120 mmHg for hexane. The mole fraction of pentane in the vapour phase would be: (a) 0.549 (b)

    		•