Account for the following
(i) Curdling of milk (ii) Tail of coments
(iii) Use of potash alum in the purification of water (iv) cleansing action of soap

Answer

(i) & (iii) are based upon concept of coagulation of colloidal sol.
(ii) Tail of comet is visible because of Tyndall effect.
(iv) The Cleansing Action of Soaps:
It has been mentioned earlier that a micelle consists of a hydrophobic like central core. The cleansing action of soap is due to these micelles, because oil and grease can be solubilised in their hydrocarbon, like centres which are not otherwise soluble in water. This is shown diagrammatically in Fig. The dirt goes out along out along with the soap micelles.
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