Scientists Say Chemistry

Scientists Say: Surface tension

This effect is what allows some bugs to walk on water

water striders

Surface tension creates just enough cohesion to hold up tiny bugs — like these water striders.

CORY/WIKIMEDIA COMMON (CC BY-SA 2.1 JP)

By Bethany Brookshire

Surface tension (noun, “SUR-face TEN-shun”)

This is an effect seen when liquid meets air. The molecules in the liquid are more attracted to each other than they are to the nearby air. This makes them clump together at the liquid’s surface. Surface tension is what makes the surface of a very full glass of water look like it is covered with an invisible membrane. It’s also why some small insects can walk on top of the water — surface tension is just strong enough to hold them up.

 

In a sentence

Soap can disrupt surface tension by making it harder for the water molecules to bunch together.

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Power Words

More About Power Words

disrupt     (n. disruption) To break apart something; interrupt the normal operation of something; or to throw the normal organization (or order) of something into disorder.

force     Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.

liquid     A material that flows freely but keeps a constant volume, like water or oil.

membrane     A barrier which blocks the passage (or flow through of) some materials depending on their size or other features. Membranes are an integral part of filtration systems. Many serve that same function as the outer covering of cells or organs of a body.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

surface tension     The surface film of a liquid caused by the strong bonds between the molecules in the surface layer.

About Bethany Brookshire

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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