How does soap help in cleaning clothes and rinsing off oil and grease?

When we say that we agitate clothes so that grease particles get separate out from clothes as ionic part of hydrocarbon chains of soap is attached to water and non polar part of chain is dissolved in oil and grease on clothes surface.


So it is said that if we shake clothes than these oil molecules get dispersed in water.Because ionic part keep attached to water thus snatching oil molecules from clothes


But how? As if we shake clothes can't the non polar part of hydrocarbon carbon chain keep attached to clothes grease and oil and keeping along the ionic part of chain with it?


I mean **Does the ionic attraction between water and hydrophilic part of chain is stronger(thus keeping the chain stable and fixed in water help in snatching out grease particle when cloth shaked)?** and that's why not keep attached to grease molecules even after rinse with water?


Basically , I am asking
"Why hydrocarbon chain snached off the oil molecules from clothes when shake and rinse with water instead of keep attached with clothes , can't ionic part of chain moved along with shaking of clothes and therefore keep oil molecules on stable clothes?"




Let's look at the system: clothes + grease + water + soap. To be more specific:


a) We prefer to wear hydrophilic materials to manage moisture removal (sweat). The clothes could be cotton, wool or linen, which are naturally hydrophilic, or synthetic, like polyester or acrylic, which are naturally hydrophobic, but are treated with a finish to make them hydrophilic, because we don’t like the feel of wearing plastic. Ref 1.


A material, whether hydrophilic or hydrophobic, can be wet by either kind of liquid, but the degree of attachment, or the ease of removal, will vary. Hydrophilic materials tend to be more polar and find ways to bind together by polar attractions, while hydrophobic (oleophilic) materials tend to bind with lower energy.


b) The grease is a long-chain hydrocarbon, a viscous, hydrophobic, oily material. Even tho the grease is hydrophobic, it will wet hydrophilic materials, and it still takes energy to get it off.


c) The soap is an alkali salt of a fatty acid: somewhat soluble in water; it ionizes at very low concentrations to a cation (+) and a long chain hydrocarbon with a negative end (carboxyl). At higher concentrations micelles form as hydrocarbon ends get close and extrude any water between them (the chain is hydro*phobic* after all). So a bunch of soap molecules agglomerate in little spheres or rods, or other shapes, with all the carboxyl groups on the outside affiliated more closely with water molecules.


Synthetic surfactants are not soaps and are very different chemically, but still have a hydrophilic end and a hydrophobic end. In the picture, the micelle on the far right is a mixed micelle, having grabbed some oil from some dirty clothes.


[![enter image description here](https://i.stack.imgur.com/Te6oW.jpg)](https://i.stack.imgur.com/Te6oW.jpg)


It's important to note that the flakes of soap, or the liquid soap, *and the micelles* are a *reservoir* of active material, and the first reaction of cleaning is done by a very low concentration of individual soap *molecules*.


d) The system also includes stirring or agitation. Chemical reactions between separate phases, like two liquids, or a solid and a liquid, almost always take place easier when there is plenty of agitation, which allows more opportunity for tiny molecular motions to do their thing.


Let's observe the process:


Case 1: Macro scale; visual observation.
If you take the oily/greasy clothes and wet them, the clean spots will get wet, but greasy spots will tend to repel water. If you wet the clothes with soap solution, everything gets wet, because the surface tension of the water is reduced. Shake the clothes in the soap solution, drain and rinse to carry away the emulsified grease, and your clothes are now clean. Like magic!


We explain the cleaning by saying that the surface tension of water is reduced by the soap so the solution can wet the grease, emulsify it and carry it away. Surface tension is like a skin formed from the outermost layer of water molecules; the skin on water can support a paper clip or a bug or resist wetting some low surface energy material like grease.


[![enter image description here](https://i.stack.imgur.com/Rbms8.jpg)](https://i.stack.imgur.com/Rbms8.jpg)


[![enter image description here](https://i.stack.imgur.com/nUhma.jpg)](https://i.stack.imgur.com/nUhma.jpg)


[![enter image description here](https://i.stack.imgur.com/MuKs3.jpg)](https://i.stack.imgur.com/MuKs3.jpg)


Surface tension does not explain everything: agitation is important to break up the grease; soap is important to encapsulate the grease into mixed micelles (which look like soap micelles, not grease droplets). Rinsing is important because it removes the excess soap (as micelles) and grease (as mixed micelles).


Case 2. Micro scale; visualize with imagination. When you put the greasy clothes into the soap solution, not much happens unless you agitate, which brings the soap *molecules* into better contact with the grease. Hydrocarbon tails find the grease, adhere and mix in. Now the grease becomes covered with soap that has its hydrocarbon end sticking in, and its carboxyl end sticking out into the water. The clothes are even dirtier! The OP’s question seems to address this very early stage of the cleaning process. But we don’t stop there - shake, shake, shake, and mechanical activity splits off a layer of grease containing the soap into the solution, where it rearranges into a mixed micelle. The reservoir of soap micelles supplies more individual soap molecules to the solution, some get onto the surface again; continual shaking knocks off more grease/oil/soap. The clothes get cleaner; the water gets greasier.


The process of mechanical agitation will continue to knock soaped up grease off more efficiently than grease can get out of a mixed micelle and get back onto the clothes. If the soap is inefficient in knocking off and trapping the grease, it will never make it to the big time.


Now you are halfway finished. You must remove the greasy water emulsion by rinsing the clothes. The clothes may be clean enough; if not, you could rinse some more, or wash again and rinse.


Ref 1. <https://www.fsw.cc/type-finish-fabric-need/>


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