Soaps are good cleansing agents. Do you know how they do this? For understanding this you should know about a ‘true solution’ and a colloidal solution.
A true solution is that in which the solute particles dispersed in the solvent are less than 1nm in diameter. A colloidal solution contains the solute known as ‘dispersed phase’ with its particles with diameters greater than 1nm but lesser than 1000 nm in the solvent known as ‘dispersion medium’.
Soap is an electrolyte. When soap is put in water in very small amount it gives low concentrated solutions. It gives true solution but, above a particular concentration known as critical micelle concentration (CMC), the soap particles get aggregated and these aggregated particles are of colloidal size known as micelles or associated colloids.
A spherical aggregate of soap molecules in water is called micelle. When soap is dissolved in water, it forms a colloidal suspension in which the soap molecules cluster together to form spherical micelles.
Take about 10 ml of water each in two test tubes. Add a drop of oil (cooking oil) to both the test tubes and label them as A and B.