What Is Capillary Action?
Capillary action is how water moves through tiny spaces—sometimes even uphill!
Capillary action happens when water climbs up small spaces, like inside a paper towel or a plant stem.
It works because of two forces:
- Adhesion – water sticks to other surfaces (like paper or glass).
- Cohesion – water sticks to itself and pulls other molecules along.
This teamwork between adhesion and cohesion lets water move without being poured or pumped.
Why Capillary Action Matters
Capillary action helps living things grow and even keeps your body working!
- Plants use capillary action to pull water from their roots to their leaves—even tall trees!
- If you dip the edge of a napkin into water, the water “walks” upward through the paper.
- Your body also uses capillary action in tiny blood vessels called capillaries, where blood moves through narrow spaces.
- This movement happens even against gravity, which makes it a superpower in nature!
Fun Facts
Here are some interesting facts about capillary action:
- Red flowers can turn blue if you place them in colored water, thanks to capillary action.
- Coffee “walks” through the filter paper using capillary action before dripping into a cup.
- Some insects, like water striders, depend on water’s surface tension (a cousin of capillary action) to walk on water.
- Food nutrients pass through capillary walls into cells, helped by tiny gaps, pressure, and capillary action.
Review
Let’s quickly recap what we learned about capillary action:
- What do we call water sticking to other things? Adhesion
- What helps water stick to itself? Cohesion
- What natural system uses capillary action to move blood? Capillaries
- What part of a plant uses capillary action to move water? Stem
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