1. The cleansing action of soap or detergent depends on their chemical bonding and
structures.
a) The ionic ‘head’ (negatively charged) is soluble in water (hydrophilic) but
insoluble in oily layer.
b) The long hydrocarbon ‘tail’ (neutral) is insoluble in water (hydrophobic) but
soluble in oily layer.
2. Oil cannot be washed away from clothing with water because oil (a covalent
molecult0 is insoluble in water.
3. Lifting greasy dirt from the surface cloth. When soap or detergent is added to the
dirty surface of a piece of cloth covered with a layer of oil or grease.
a) The negatively charged ‘head’ (hydrophilic) of soap ions or detergent ions
dissolves in water.
b) The hydrocarbon ‘tail’ (hydrophobic) of soap or detergent ions dissolves in
the layer of grease.
4. I the water is agitated slightly, the grease begins to be lifted off the surface. This
cause by the forces of attraction between the water molecules and the negatively
charged heads.
5. On further agitation during washing, the greasy dirt is lifted from the surface.
6. Emulsifying dirt in water
a) Soaps and detergents can act as emulsifying agents to emulsify oils and
grease.
b) The process of emulsification breaks large drops of grease into smaller
droplets that floats in water. The greasy droplets repel on another because
they carry the same charge. As a result, the grease is suspended in the
solution.
c) When the cloth is rinsed with the water, the droplet will be carried away.
d) The cleaning process become more efficient in the water containing the
soap or detergent solution is stirred