C.4.4

=Describe the hydrolysis of fats to form soaps and the action of soaps.= Soap is the salt of the fatty acid produced.
 * Saponification** is the process of hydrolysis of fat into its constituent //glycerol// and //fatty acids// by boiling with alkali (NaOH or KOH)

Saponification of a fat with sodium hydroxide.



3 Na+ ions are required to saponify one fat molecule. These will replace the glycerol, yielding three fatty acids with an Na+ tail.

A soap essentially is a fatty acid salt. Usually it is the sodium salt of a fatty acid; sometimes the potassium or sodium salt. In either case, they are usually made from the hydrolysis of a fat of some kind to form glycerol and the fatty acid.

(non polar, water insoluble end) **CH3-(CH2)n - COONa** (polar, water soluble end)

(read explanation below)

Soaps function because their long non-polar hydrophobic 'tail' dissolves in oil or grease to form a **micelle**. A **micelle** is __an aggregate with a water-loving (hydrophilic) surface and a fatty core, consisting of a few dozen and up to many thousand molecules, the precise number being given by the aggregation number.__ __Most micelles are spherical, disk-like, or thread-like, but other forms are possible.__ This micelle is surrounded by the polar hydrophilic 'heads' of the soap molecules, which make it soluble in water. Soaps don't work well in hard water as the Ca2+ and Mg2+ ions present in the water cause the precipitation of the insoluble Ca or Mg salts of the fatty acids known as 'scum'.