structural:expansion, stylistic:style_transfer, structural:scholar_edition
Toilet soaps

In a domestic setting, "soap" usually refers to what is technically called a toilet soap, used for household and personal cleaning. Toilet soaps are salts of fatty acids with the general formula (RCO)M, where M is Na (sodium) or K (potassium).

When used for cleaning, soap solubilizes particles and grime, which can then be separated from the article being cleaned.The insoluble oil/fat "dirt" become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water, making them soluble. Anything that is soluble will be washed away with the water. In hand washing, as a surfactant, when lathered with a little water, soap kills microorganisms by disorganizing their membrane lipid bilayer and denaturing their proteins. It also emulsifies oils, enabling them to be carried away by running water.

When used in hard water, soap does not lather well but forms soap scum (related to metallic soaps, see below).