NCERT Question 8 - Chapter 4 Class 10 - Carbon and its Compounds

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Answer:

A soap molecule consists of two different ends which have different properties . One end is hydrophilic i.e. water loving and the other end is hydrophobic i.e. water fearing . The hydrophilic end dissolves in water but the hydrophobic tail end doesn't. 

When the soap is added to water, two orientations of the molecules can be seen:

1. In the soap molecules on the surface of wate r , since the hydrophobic ‘tail’ is insoluble in water, the soap molecules align them along the water surface in such a way that the ionic end is inside water and the hydrophobic part faces outwards .
2. But when these molecules are completely inside water , they have a very unique orientation which keeps the hydrophobic part outside water . In this type of arrangement, a cluster is formed in which the hydrophobic tails are in the interior of the structure and the hydrophilic ones are on the cluster’s surface. This formation is known as micelle .  

Since the hydrocarbon chains (water fearing) of soap are soluble in ethanol , micelle formation will not take place in ethanol .