Why does soap remove dirt and how does soap wash away dirt?

There is something called sodium of higher fatty acids in soap. It is shaped like a long chain, one end of the chain likes oil stains, while the other end likes water. When the stain is rinsed with water, the dissolved end will pull the oily end into the water, and the oil stain will fall into the water, and the clothes will be clean.

The clothes are dirty because they are stained with dust, soot, grease and sweat. There is something in soap (sodium stearate) that dissolves the dirt in water. So, soap can remove stains...

Helping others is the foundation of happiness, and the molecular structure of soap can be divided into two parts. At one end is the charged polar CoO- (hydrophilic site) and at the other end is a non-polar carbon chain (lipophilic part). Soap can destroy the surface tension of water, when the soap molecules enter the water, the polar hydrophilic part, will destroy the attraction between the water molecules and reduce the surface tension of the water, so that the water molecules are evenly distributed on the surface of the clothes to be washed.

The lipophilic part of the soap penetrates deep into the oil stain, and the hydrophilic part dissolves in the water, and this conjugate is stirred to form smaller oil droplets, and its surface is covered with the hydrophilic part of the soap, and will not re-aggregate into a large oil stain. This process (also known as emulsification) is repeated several times, and all the oil stains are dissolved in water as tiny droplets that can be easily rinsed off.

Ingredients of soap: sodium salt R-Co2Na of carboxylic acid, synthetic coloring, synthetic fragrance, preservative, antioxidant, foaming agent, hardener, viscous agent, synthetic surfactant. The main ingredient of soap, R-CO2NA, (sodium stearate (C17H35COONA)), in which the R group is generally different, is a variety of hydrocarbon groups.

r- is a hydrophobic group and a carboxyl group is a hydrophilic group. In hard water, soap and Ca2+, Mg2+, etc., form curd-like substances, fatty acids, calcium salts, etc., which are commonly referred to as "calcium soaps" and become useless descalers. Adding a softener to hard water removes hard water ions, allowing the soap to function and bind to the oil molecules, creating a precipitate.

The decontamination of soap is the role of sodium fatty acids, which can be divided into two parts, one part is a polar hydrophilic group-coona, which is soluble in water, and the other part is a non-polar chain hydrocarbon group-R, which is a hydrophobic group and has lipophilicity.

When washing, the oil stain and the soap come into contact, and -R can be inserted into the oil droplet, and the -coona dissolved in water is placed on the outside of the oil droplet, so that the oil is surrounded by soap molecules, and then through friction, etc., the large oil stain is dispersed by very small oil beads, and finally separated from the clothes and dispersed into the water to form an emulsion, which belongs to the emulsification reaction and is a physical change.