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A molecule with two ends

How Does Soap Clean?

Soap molecules grip grease at one end and water at the other, so grease can be rinsed away.

1 One end of themolecule gripsgrease2 The other endgrips water3 Grease iscarried away inthe rinse
A translator between two things that refuse to mix.

  1. Step 1 of 5

    Water alone cannot shift grease.

    Water and water Stick togetherWater and greaseRefuse to mix

    Water molecules stick to each other and to other water-friendly things. Grease is neither, so water just rolls off it.

  2. Step 2 of 5

    Soap molecules have two different ends.

    One end loves waterThe other end lovesgrease

    One end is attracted to water, the other to grease. Each molecule can bond to both — that is the entire trick.

  3. Step 3 of 5

    They surround each drop of grease.

    A grease droplet Soap molecules pointinginward, water-friendlyside out

    Grease-loving ends dig into the drop and water-loving ends face outward. The result is a ball with a water-friendly surface.

  4. Step 4 of 5

    Now water can carry it off.

    1 Grease wrapped2 Water can nowgrip it3 Rinsed away

    The wrapped droplet looks water-friendly to the water around it, so rinsing lifts it away — grease and all.

  5. Step 5 of 5

    It also tears apart many germs.

    Germ with a fatty coat Intact and infectiousAfter soapCoat torn apart

    Many viruses are wrapped in a fatty envelope. Soap pulls that apart exactly as it pulls apart grease, which is why hand washing works so well.

    Soap has been made for over four thousand years, long before anyone understood why it worked.

The short version

Soap molecules grip grease at one end and water at the other, letting rinse water carry grease and germs away.

Try it yourself

Put pepper on water and touch the surface with a soapy fingertip. The pepper flees instantly.

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