Pure oil and pure water shaken together separate into two layers again on standing, but with a small amount of soap the dispersion persists. The main reason for the separation without soap is that:

1. Aoil and water react chemically on standing
2. Bcoalescence of droplets decreases the total oil-water interfacial area and hence the interfacial free energy
3. Cthe droplets gain a large charge of the same sign and attract each other
4. Dthe droplets become smaller until they dissolve in water