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What is capillary action?

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Quick answer

Capillary action is the ability of a liquid to flow upward through narrow spaces against gravity, like water climbing up a thin tube or a paper towel. It happens because the liquid's molecules are attracted to the surface and to each other.

Key things to understand

  1. Liquid rises through narrow spaces against gravity.
  2. It's driven by attraction to surfaces (adhesion) and itself (cohesion).
  3. Thinner tubes pull liquid higher.
  4. It's how plants draw water up and towels soak up spills.

People also ask

What is capillary action?
The movement of a liquid up through narrow spaces, against gravity, due to adhesion and cohesion.
What's an example of capillary action?
Water climbing up a paper towel, or a plant drawing water from roots up to its leaves.
Why does capillary action work better in thin tubes?
Narrower spaces increase the surface attraction relative to the liquid's weight, lifting it higher.

Part of the guide: Water & Weather Phenomena →