It is the fat or the oil that especially makes things dirty. Everyone knows how oil catches dust and makes a mess on one’s hands and clothes. It is the oil that comes out of the head, where the hair is, that makes us dirty so quickly; and the same applies to other things. Now, if we can melt or get rid of the oil on things, we can soon make them clean, and the real use of soap is that – it disposes of oil. It does this in at least two ways.
Most soaps have in them a great deal of something we call alkali. This alkali simply dissolves the oil that gathers on things, and so it makes them clean. But soap takes away the dirt from things in another way, as we know when we use soaps that have no alkali in them at all. It has the power of breaking up oil into number of very tiny little drops, which are easily washed away, together with all the dirt that the oil has caught and collected.
A collection of very tiny drops of oil, held in some other fluid, is called an emulsion. Water alone will not form an emulsion of any oil, because oil and water will not mix. That is the reason why we cannot wash well with water alone. But when water has soap dissolved or melted in it, it is able to make an emulsion of the oil on anything we are washing, and so makes it clean.
Additionally, soap, oils, and water are all made of molecules. While some molecules are attracted to water, others are repelled by water. There are two other things that we need to know about and that are polar and non-polar. Grease and oil are non-polar compounds that do not mix with water, whereas polar compounds dissolve in water. When it comes to soap, it can dissolve in both water and oil, why? The thing is that soap has two ends that are different. One end is polar while the other is non-polar.
When soapy water comes in contact with oily or greasy compounds, the molecules of soap arrange themselves in micelles, which are tiny clusters. The molecules of soap that are poplar, stick to water, whereas the molecules that are attracted to oil and grease are trapped in the center, which does not allow them to come in contact with the water. Since the oil is trapped in the center, and the micelle dissolves in water. Upon using the soapy water, the oil and grease wash away as well.
In simpler words, the two ends of the soap perform differently by attracting oil and grease and then tears the oily molecules by using its water-loving molecules to trap it in the center. You might have noticed that washing hands with warm water as compared to cold water is more effective. The reason is that oils and fats soften or melt when exposed to warm water. This causes them to attach themselves to the soap molecule’s hydrophobic ends, ultimately resulting in washing away oil and grease easily.
Furthermore, soap is a natural surfactant, any substance could be termed as a surfactant if it reduces the surface tension of the liquid in which it is dissolved. With that being said, almost every cleaning product consists of surfactants. Not only do they reduce the surface tension of the liquid, but they are manufactured in a way that they have two ends, which allows them to become compatible with both water and oils, etc. In the presence of surfactants, the water molecules become slippery and are more likely to interact with oil and grease molecules as compared to themselves. Therefore, this property makes them an ideal option for washing hands and crockery, etc.
Lastly, natural soaps do not require any artificial or synthetic additives for them to clean or lather since they are natural surfactants. You might have thought they are only good at creating foam and bubbles but, in reality, perform an excellent job of cleaning hands and removing oil, etc.