Question

People use many methods to wash the clothes. Usually, after adding the soap, they beat the clothes on the stone, or beat it with the paddle, scrub it with the brush or the mixture is agitated in the washing machine. Why is agitation necessary to get clean clothes?

Answer 1

Hint: When the soap is added with the clothes it forms micelles with the dirt due to its hydrophobic part. Then, these micelles formed remain suspended as the colloid. Hydrophobic part of the soap is the part which is repelled from the water.

Complete Step by Step Solution:
At first, we need to look at the working of soap –
Soap, water and oil all are made up of molecules. The soap has two parts one is a hydrophobic part and another one is a hydrophilic part. The hydrophobic part of the soap can be defined as the part of the soap which is repelled by the water or it does not get attracted towards the water while the hydrophilic part of the soap can be defined as the part of the soap which gets attracted towards the water. The hydrophilic part readily mixes with the water. As the water and oil cannot be mixed, the hydrophilic and hydrophobic part also does not get mixed. The hydrophobic part of the soap attracts the dirt, oil, grease etc. towards it while the hydrophilic part dissolves in the water. Then, this attraction of dust towards the hydrophobic part forms the micelles which remain suspended as the colloid. So, to remove the form of dirt as micelles the agitation becomes necessary, so that the dirt is removed from the clothes and they look clean.

Note: In the micelles, the carboxylate groups form a negatively-charged spherical surface, with the hydrocarbon chains inside the sphere. Because they are negatively charged, soap micelles repel each other and remain dispersed in water.