Soap may be represented by the formula RCOONa where R is an alkyl group which represents a long chain of carbon with fifteen or more atoms. Now, oil drops containing dirt particles and water do not mix. Soap helps in their mixing by reducing interfacial tension or friction. Actually it forms a sort of bridge between oil drops and water in which the alkyl portion (hydrophobic end) points towards oil drop while other portion COON a (hydrophilic end) is directed towards water. This is known as micelle formation. Thus, soap helps in the formation of a stable emulsion between oil and water. Ethanol and other similar solvents which are of organic nature do not help in micelle formation because soap is soluble in them.