The principle behind the cleansing action of soap lies in the effectiveness of sodium salts of higher fatty acids. These salts can be divided into two components: one part consists of a polar hydrophilic group, COONa, which is soluble in water, while the other part comprises a non-polar hydrophobic chain, R, which repels water and possesses oil-loving properties. When washing clothes, the hydrophobic chain of the soap molecule dissolves into the oil or grease, while the hydrophilic carboxylate group extends into the surrounding water. The oil or grease becomes surrounded by soap molecules, forming stable emulsions. Through mechanical rubbing and rinsing with water, the dirt and oil separate from surfaces, dispersing into smaller emulsion droplets in the water, subsequently carried away with the rinsing water.
Principles of Soap Cleaning Oil and Grease
When soap dissolves in water, at the water surface, the hydrophilic carboxylate part of the soap molecule tends to enter the water molecules, while the hydrophobic hydrocarbon chain is repelled, staying outside the water, forming an oriented arrangement of soap molecules. This presence of a layer of higher fatty acid salt weakens the attraction between water molecules on the water surface, allowing soap to significantly reduce the surface tension of water, hence acting as a surfactant.
Principles of Soap Cleaning Oil and Grease
When soap concentration in water is low, soap molecules exist as single entities, congregating at the water's surface with hydrophilic groups entering the water and hydrophobic groups repelled outside. As the soap concentration in water gradually increases, the number of soap molecules amassing on the water's surface grows to form a monolayer. Further, increasing soap concentration leads to the saturation of the water's surface, causing the hydrophobic hydrocarbon chains within the water solution to gather due to van der Waals forces while the hydrophilic carboxylate groups envelop them, creating colloidal-sized aggregates known as micelles.
WhatsApp: 8618948240310
Email: Minajiang@boymay.net
No. 691, Science & Tech industrial park, Yongshi road, Shiwan town, Boluo county, Huizhou city, Guangdong province, China
