How Does Soap Work?

Posted by Rob on Aug 2nd 2016

You know it cleans, but how does it do that? Soap is made of chain-like molecules with one end (the polar “head”) attracted to water, and the other end (the hydrocarbon “tail”) attracted to oil.

(graphic from the Interactive Library)

When you soap up your hands the oil-attracted end sticks to the oils in your skin, and the water-attracted end sort of waves up into the water.

When you scrub your hands, the soap molecules rearrange themselves into little droplets (micelles) with the water-loving heads on the outside of the droplet, and the oil-loving tails on the inside of the droplet, trapping oils and dirt inside and allowing them to float freely in water.

This allows the oils (which are not normally water soluble) to be pulled from the skin and suspended in the water because they’re trapped inside the little droplets.

When you wash the soap away with water, the soap molecule droplets with their payloads of grease and dirt are easily washed away, too.

(graphic from the Interactive Library)