Question

Explain the terms in detail : Lyophillic colliods and Lyophobic colloids.

Give a brief set of difference between them.

Answer 1

Lyophilic colloids:
The meaning of the word 'lyophilic' is 'liquid-loving' or 'solvent attracting'. That means, these are colloids in which there is strong interaction between the two phases.
Lyophilic colloids are those dispersions in which the dispersed phase exhibits a definite affinity for the medium and as a results extensive solvation of the colloidal particles takes place. They are directly formed by mixing the two phases.Eg :- Gum, soap, starch, gelatin, rubber etc.
These sols are also called reversible sols. Because, if the dispersion medium is separated from the dispersed phase, the sol can be reconstituted by simply mixing with the dispersion medium.
Lyobhobic colloids
The word 'lyophobic' means 'liquid hating', ie, in these sols there is little or no interaction between the two phases.
Lyophobic sols are those dispersions in which there is very little attraction between dispersed phase and dispersion medium,
They cannot be prepared by simply mixing the two phases. Eg :- Dispersion of metals in water, colloidal hydroxides etc.
They are irreversible in nature. Because, once precipitated, they do not given back the colloidal sol by simple addition of the dispersion medium.


Difference
1 definition:
Lyophilic ; solvent loving colloids
lyobhobic; solvent hating colloids

2. Stability:
Lyophilic; thermodynamically stable
Lyobhobic; thermodynamically unstable

3.Reversibility:
Lyophilic; precipitation in lyophilic solvent is reversible process
Lyobhobic ; precipitation is irreversible

4.Interaction:
Lyophilic; strong bond of attraction between colloids and liquid
lyobhobic;less or no interaction

5.viscosity
Lyophilic ; highly viscous
Lyobhobic ; same viscosity as that of solvent

6.water as solvent:

Lyophilic;When water is taken as the solvent, lyophilic colloids are known as hydrophilic colloids.

Lyobhobic; When water is taken as the solvent, lyophobic colloids are known as hydrophobic colloids.

7.Preparations

Lyophilic; prepared by the direct addition of dispersion phase (colloids) into dispersion medium (liquid).

Lyobhobic; can be formed from special techniques such as mechanical agitation.