Try taking a greasy plate and washing it under cold running water. We can say with complete confidence that nothing will come of this venture. You can remove the sticky oily film only by adding a little soap to the water. Consisting of a variety of fat, it surprisingly dissolves any dirt and makes objects sparkling clean.
Grease, dirt and water
Most types of mud to one degree or another contain fat, and even if not, the same dust, settling on the skin, mixes with sebum, therefore, simply rinsing your hands with water, you cannot consider them clean. Fat does not dissolve in water. If you mix water with a small amount of vegetable oil in a glass, you can see how the liquid separates into 2 components that do not want to have any connections with each other.
You can mix it indefinitely, the maximum that can be achieved is an aqueous suspension of oil droplets, the so-called suspension. The picture changes to the sharply opposite, if a little soap is dropped into the same glass. Three substances - water, oil and soap will combine into one, that is, soap will simply dissolve fat in water - finally and irrevocably.
How soap works
This dissolution process takes place as follows. Soap belongs to the category of so-called tensides and, like many other substances, consists of many tiny particles - molecules. The surfactant molecules have one remarkable feature. One side of the molecule is capable of attracting water, the other, on the contrary, repels it. Scientists call them hydrophiles and hydrophobes, respectively. Hydrophobes, in turn, are able to attract fat particles to themselves.
Thus, a kind of chain is obtained. A water molecule is attached to the tenside particle on one side, and a fat molecule on the other. That is, the fat dissolves, as it were, without leaving the slightest trace behind. All that remains is to wash off the resulting substance from a plate, hands or any other item that needed to be washed.
Soap production
Most of the soaps produced today are made from vegetable or animal fats by adding alkalis to them - potassium or sodium. A chemical reaction occurs, the result of which is the decomposition of fats into glycerin and fatty acid salts. The consistency of the soap obtained depends on the length of the chains of the tensides formed. If stearic acid or palmitic acid salts are formed as a result of the reaction, the soap will be hard.
In this case, it also matters which alkali was used in the production. It is known that potassium salts in soap make it more plastic and hydroscopic, that is, liquid. But any soap, from household to cosmetic, uses the same principle of affecting dirt - it dissolves it together with fat and is safely washed off, taking with it newly acquired “friends”.
