How Soap Destroys Germs

A two-faced molecule, round head and wiggly tail, diving its tail into a blob of grease; a virus coming apart at the seams; a twenty-second clock beside a bottle of hand sanitiser.

Before you start. You already know that oil and water refuse to mix, and that germs like the flu virus or a cold virus are too small to ever see. That is the whole of the background this needs.

The idea in 30 seconds

Soap works because its molecules are shaped like tiny two-faced tadpoles: a head that’s happy in water, a tail that isn’t.
It isn’t that the tail “hates” water - water pushes greasy tails together to keep its own tidiness everywhere else, and the tail has no say in it.
Those tadpole tails wrap a speck of grease into a tiny ball, a micelle, and rinsing carries it, and whatever was riding in the grease, down the drain.
Some viruses, like flu and the coronavirus behind covid, wear a stolen envelope borrowed from a cell they infected, and the same tadpole tails that wrap up grease wedge into that envelope and take it apart.
Other germs, like cold viruses and norovirus, have no envelope at all, just a hard shell - against them, soap only washes, it doesn’t destroy.
Twenty seconds isn’t reaction time for the chemistry, which is over in an instant - it’s time to scrub into every crease and rinse the whole mess away.

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