What Does It Mean? 🤔
Let's learn together
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Cohesion is the attraction water molecules have for each other. Because water molecules are pulled toward one another, they tend to stick together rather than spreading apart.
This cohesive stickiness is part of what makes surface tension possible, and it is also part of why water can travel up through narrow tubes during capillary action — the molecules pull each other along!
You can see cohesion in action when water forms a round droplet instead of flattening out completely, or when two small drops of water touch and instantly merge into one bigger drop.
See It in Action! 👀
Real examples
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Water forms round droplets because of cohesion between molecules!
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Cohesion helps water bead up on a waxy leaf instead of spreading flat!
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Cohesion helps water molecules pull each other up a paper towel!
For Grown-Ups! 👨👩👧
Help kids learn
👨👩👧 Teaching Tips
Pair cohesion with adhesion in discussion so kids understand the difference: cohesion is water sticking to itself, while adhesion is water sticking to something else.
🏫 Classroom Ideas
Drip water onto a waxy surface like wax paper and onto a paper towel side by side, letting students compare how the droplet behaves differently and connect it to cohesion versus adhesion.