Question

Explain the mechanism of the cleaning action of soaps

NCERT Class X
Science - Science

Chapter_Carbon and its Compounds

Answer 1

Cleaning action of soap has been explained with the help of fig. Soaps are molecules in which the two ends have differing properties, one is hydrophilic, that is it dissolves in water, while the other end is hydrophobic, that is it dissolves hydrocarbons. When soap is at the surface of water the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic ed in water and the hydrocarbon ‘tail’ protruding out of water. Inside water, these molecules have a unique orientation that keeps the hydrocarbon portion out of the water. This is achieved by forming clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle. Soap in the form of a micelle is able to clean, since the oily dirt will be collected in the centre of the micelle. The micelles are large enough to scatter light. Hence a soap solution appears cloudy.

Answer 2

Each soap molecule has two ends. These are:

Polar, ionic hydrophilic end (water loving part)

Non-polar, non-ionic hydrophobic end (water hating part)

Dust or oil are hydrophobic in nature.
Mechanism of cleansing action of soap:
I. Soap gets dissolved in water.
ii. The non-polar ends get directed towards the centre and the polar ends get directed outwards.
iii. A cluster comprising of this arrangement is formed which is known as micelle.
iv. Dirty cloth is put in soap solution.
v. Non-polar end gets attached to the oil or dirt present in the cloth and polar end remain attached to water.
vi. Dirty cloth is agitated in soap solution.
vii. Oily and greasy particles entrapped in soap micelle gets dispersed in water.
vii. Soap water gets dirty and the cloth gets cleaned.