Soap contains the cleaning property because nonpolar oil that carry dirt dissolve in the nonpolar interior of the micelle and are carried out away with the soap during rinsing.

Since soap can undergo precipitation (soap scum) in hard water due to reaction with calcium and magnesium ions, synthetic soaps (salt of benzenesulphonic acid) called detergents have been developed that don’t form soap scum in hard water. 

Scheme 6