--%>
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 : Molecular Properties Symmetry Molecular

    Molecular orbitals and molecular motions belong to certain symmetry species of the point group of the molecule.Examples of the special ways in which vectors or functions can be affected by symmetry operations are illustrated here. All wave functions soluti

    		•
  • 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 decomposition reaction

    Nitrogen tetroxide (melting point: -11.2°C, normal boiling point 21.15°C) decomposes into nitrogen dioxide according to the following reaction: N2O4(g) ↔ 2 NO2(g)<

    		•
  • Q : Acid value definition The acid value

    The acid value definition is the number milligrams of KOH needed to neutralize the acid present in one gram oil and fats however why not employ NaOH for the neutralization?

    		•
  • Q : Problems related to entropy change A)

    A) Two compartments each of 1 m3 capacity are joined by a valve and insulated from the surroundings and from one another. One compartment has saturated steam at 683.6 kPa and the other contains steam at the same temperature but at a pressure of 101.3 kPa. T

    		•
  • Q : Molarity of Barium hydroxide 25 ml of a

    25 ml of a solution of barium hydroxide on titration with 0.1 molar solution of the hydrochloric acid provide a litre value of 35 ml. The molarity of barium hydroxide solution will be: (i) 0.07 (ii) 0.14 (iii) 0.28 (iv) 0.35

    		•
  • Q : Chem Explain how dissolving the Group

    Explain how dissolving the Group IV carbonate precipitate with 6M CH3COOH, followed by the addition of extra acetic acid.

    		•
  • Q : Theory of three dimensional motion

    Partition function; that the translational energy of 1 mol of molecules is 3/2 RT will come as no surprise. But the calculation of this result further illustrates the use of quantized states and the partition function to obtain macroscopic properties. The partition fu

    		•
  • Q : Molar conductance what is the molar

    what is the molar conductance of chloropentaamminecobalt(III) chloride?

    		•
  • 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

    		•