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nas1 nas1
wrote...
9 years ago
How do soaps work, chemically speaking? Describe their chemical properties and give an example (including chemical formula) of a particular soap.
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wrote...
9 years ago
Are you familiar with the term "surfactant" ? Or more simpler, what a "base" is?

Surfactants have a hydrophilic side of the molecule attaches to water, and a hydrophobic side of the molecule that avoids water. To explain a bit more in detail, in the absence of oils, the hydrophobic side sticks out of the surface of the water drop. There is no longer any water at the surface to form a strong surface tension, so the water no longer beads up, but spreads. The hydrophobic end of the molecule is also free to attach to grease, fat, or oil on the surface, aiding in the spreading.
This is one of the reasons that you use soap when you wash your dishes with water.
rsb
wrote...
9 years ago
Water molecules are "polar", they have a plus and a minus side. Oil is non-polar. Soap molecules have a polar side that will stick the water and a non-polar opposite side that will stick to oil and other non-polar things.

A surfactant covers the polar water molecules and allows them to lay flat and stick to non-polar things.
wrote...
Staff Member
9 years ago
A modern soap will contain a mixture of chemicals which help cleaning.

But the major action is due to the molecules and the distribution of charges in the molecule. Most soaps are sodium or potassium fatty acids salts, Each soap molecule has a long hydrocarbon chain, sometimes called its ’tail’, this part of the molecule has a similar charge distribution to oils so it can mix with oils.

The carboxylate ’head’. In water, the sodium or potassium ions float free, leaving a negatively-charged head. this has a similar charge distribution to the water.

The effect of this is that you have a molecule where the head will be most stable in the water and the tail will be most stable in the grease or oil. As more molecules arrive and become aligned the action of this is to drag the oil into the water. In the water the molecules soap molecules act as a protective layer on the oil keeping it in the water acting as an emulsifying agent

Another factor that is often forgotten is that the sodium or potassium fatty acids salts also act as a very weak alkali and react or remove a very thin layer the skin effectively removing small amount of skin. This is what makes soap feel soapy.

A surfactant is a chemical that makes water wetter by reducing the surface tension.
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