Did you wash your hands? Did you use soap?

Children everywhere are grossly familiar with those questions, but it's for a good reason: Washing with soap is essential for preventing the spread of germs that make us sick.


Germs, or microbes, are everywhere. Literally, everywhere. In the air, soil, water and on every surface, including your body. Most microbes are harmless and some are important for human health, like the ones that live in our gut. But there are several germs that cause problems, and these are the ones we prefer not to have on or in our bodies. Our first line of defense against those harmful germs is soap.


Soaps are sodium or potassium fatty acids salts, produced from the hydrolysis of fats in a chemical reaction called saponification. Each soap molecule has a long hydrocarbon chain, sometimes called its 'tail', with a carboxylate 'head'. In water, the sodium or potassium ions float free, leaving a negatively-charged head.


How Soap Cleans

Soap is an excellent cleanser because of its ability to act as an emulsifying agent. An emulsifier is capable of dispersing one liquid into another immiscible liquid. This means that while oil (which attracts dirt) doesn't naturally mix with water, soap can suspend oil/dirt in such a way that it can be removed.


The organic part of natural soap is a negatively-charged, polar molecule. Its hydrophilic (water-loving) carboxylate group (-CO2) interacts with water molecules via ion-dipole interactions and hydrogen bonding. The hydrophobic (water-fearing) part of a soap molecule, its long, nonpolar hydrocarbon chain, does not interact with water molecules. The hydrocarbon chains are attracted to each other by dispersion forces and cluster together, forming structures called micelles. In these micelles, the carboxylate groups form a negatively-charged spherical surface, with the hydrocarbon chains inside the sphere. Because they are negatively charged, soap micelles repel each other and remain dispersed in water.


Grease and oil are nonpolar and insoluble in water. When soap and soiling oils are mixed, the nonpolar hydrocarbon portion of the micelles break up the nonpolar oil molecules. A different type of micelle then forms, with nonpolar soiling molecules in the center. Thus, grease and oil and the 'dirt' attached to them are caught inside the micelle and can be rinsed away.


With the development of modern scientific method, soaps are made into different types for specific usages, such as bath soap, handmade soap, laundry soap, soap with box case and so on. And as showers for babies, you have to be more careful. There are other items you have to perpare in advance, like diapers, toothpaste and body butter.