Tuesday, January 15, 2013

Beauty of Science #6: Soap

Last time we talked about oils, and now we'll talk about soaps. They are a rather brilliant way of using the contrasting properties of polar and non-polar molecules together.

Non-polar molecules are hydrophobic (water-fearing), and polar molecules are hydrophilic (water-loving), because, as you remember, water is also polar. Soap molecules consist of both components: a non-polar tail and a polar head. Let's look at sodium stearate, a common soap molecule.

The hydrophobic tail binds to the non-polar oils on our skin; the hydrophilic head binds to water. In this manner, we can wash away the dirt and oily substances that build up on skin.
The hydrophobic tails clump together because they want to keep water out. They don't like it. Like sticks to like!

And I think that is the shortest, most to-the-point BoS post yet! For past Beauty of Science posts:

BoS #1: A Primer and Some Food for Thought
BoS #2: Antioxidants and Free Radicals
BoS #3: UV Radiation, Visible Light, Color
BoS #4: Sunscreens
BoS #5: Oils vs. Water (Polarity)!

Resources and other good reads:
ChemMatters Oct 2011: Demystifying Gross Stuff