When soap molecules are in water, their hydrocarbon groups combine with each other by van der Waals force to form a sphere, on which the-COO (-)Na(+) part is exposed. In this way, when soap is dissolved in water, many small balls wrapped by hydrophilic groups are formed and dispersed in water. Soap is rubbed on oily clothes, hydrophobic groups like oil, and then inserted into oily clothes, hydrophilic groups hate oil, and then inserted into water molecules. After scrubbing with both hands, the oil is dispersed into fine particles, the hydrocarbon group in soap molecules is dissolved in the oil particles, and the carboxyl group is left outside the oil particles.
In this way, every tiny oil particle is surrounded by many hydrophilic groups, suspended in water and becomes emulsion. This phenomenon is called emulsification. It's like dozens of steel cuttings on a big stone, and everyone worked hard to lift it out. Rinse with water and it will be clean. This is a decontamination principle of modern detergents. Adding foaming agent, colloid solvent, perfume, wetting agent, etc. to form detergent. Detergents in modern Japan are made of colorful soap chips. The research shows that the length of carbon chain has a great influence on the decontamination ability. If it is too long, the solubility becomes smaller, and if it is too short, the decontamination ability is poor. Now scientists are exploring the length, what kind of hydrophilic groups and what kind of hydrophobic groups are the best. I hope tomorrow!