How Does Soap Work?

Soap is one of those things that you usually do not think about. You use it constantly and it is everywhere. But, how does this magical liquid, sold around the world, actually clean?

It is first important to break down what soap is in its most basic form. Soap is a combination of an acid and a base. The acid in this soap compound is a fatty acid and triglycerides. The base of this compound is usually sodium hydroxide. When the combination of the two acids and bases occur it creates a process of saponification. Saponification is the process of turning an oil, fat, or lipid into a salt by binding it with an ion. In this case, triglycerides will separate from the fatty acids to let the fatty acid bind with a sodium hydroxide ion. This combination creates a salt or what is commonly called soap in this case.

Saponification-The process of Making Soap (Theory) : Class 10 : Chemistry : Amrita Online Lab

So, why is this special combination of acids and bases create a compound that we use to clean our hands, body, dishes, and hundreds of other things? The salt that is created from saponification is an amphipathic molecule. This means that one end of the molecule is polar while the other end of the molecule is non-polar. In other terms, the polar end of the molecule can bind to things such as water and is termed the hydrophilic end. The non-polar end of the molecule is “afraid” of water and binds to things such as oils and grease.

When applying soap to your hands, dishes, and body these amphipathic soap compounds will arrange themselves around particles of oil, dirt, grease, and bacteria using their hydrophobic ends. This creates a capsule around the targeted substance and when you rinse with water, the hydrophilic ends help carry the capsule away and down the drain. This is why washing with water does not work well, because water does not attach to oils.

What are the differences between soaps though? The main difference between soaps is the kinds of acids, bases, scents, textures, and amount of water mixed with the soap. Some of these characteristics will lead to a stronger soap such as a stronger hydrophobic molecule. Other characteristics are to make the soap more enjoyable for the customer.

One of the most common misconceptions of soap is that it kills bacteria and pathogens. This is far from true. As shown before, soap does not kill bacteria and pathogens but, removes them from the surface. Oftentimes, you will find that companies label their soaps Antibacterial or Antimicrobial. In a sense, this is very true, but for it to remove 99.9% of germs as it says, you would have to keep most soaps and disinfectants on the area for at least two minutes. This is why surgeons are required to wash for five minutes!

Published by pensmenger

I am a Biology Major attending Arcadia University. I started the company My Biology Experience in hopes to connect the Biology community on a closer level.

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