What are lyophilic and lyophobic sols ? give one example of each type. Why are hydrophobic sols easily coagulated ?

Lyophilic - lyophilic (liquid loving) this sols formed by direct mixing of substances like gum starch etc. with suitable liquid, called as lyophilic sols. This are called as reversible sol because if dispersion medium is separated from the dispersed phase it can be reconstructed just by mixing them. This sols are quite stable. Ex-Protein, Starch.

Lyophobic -lyophobic (liquid hating) this sols don't formed by direct mixing of dispersed phase and dispersion media they require special methods for preparation. Ex-Sols of metal sulphides .

This Lyophobic(Hydrophobic-water hating) sols gets easily coagulated. Because they are less stable. Their stability is only due to Charge If electrolyte is added to it opposite charge will attract and form coagulation easily.