How Does Soap Work?
(Q&A by Aaron Chilcott)
Even though we use soap to remove dirt everyday, do we really understand how it
works? Let's say you have a dirty shirt. The dirt on your shirt at the molecular
level has a charge opposite to the charge on the shirt fiber. This opposite charge
is what makes the dirt stick to the shirt. When you introduce soap and water,
the water surrounds the dirt and the fiber. It forms an electrical double layer
between the dirt and the fiber. Some water molecules join with the fibers and
other water molecules join with the dirt particles. These new molecular structures
almost always have similar electrical charges which repel each other. Although
water alone has a small cleaning effect, you usually need soap. When soap is introduced,
it increases the negative charge on both molecular structures. Since the dirt
and the fiber are no longer attracted to each other, they separate and the shirt
is clean. That is how soap works.
Source: http://www.cleaninglink.com/Cleaning_Library/how_soap_works.htm
