Skip to content
Know.itKnow.it
Create an animated lesson
On request

This article is free to read. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

What is surface tension?

ScienceLesson on requestFree to read

Quick answer

Surface tension is the 'skin-like' force at the surface of a liquid, caused by its molecules pulling on each other. It's why water forms droplets, why some insects can walk on water, and why a gently placed paperclip can float.

Key things to understand

  1. It's the cohesive force at a liquid's surface.
  2. Molecules pull on each other, tightening the surface.
  3. It lets water form droplets and beads up.
  4. It supports light objects and water-walking insects.

People also ask

What is surface tension?
The force at a liquid's surface from its molecules attracting each other, making it behave like a thin skin.
Why can some insects walk on water?
Surface tension creates a film strong enough to support their light weight without breaking.
How does soap affect surface tension?
Soap lowers water's surface tension, which is part of how it helps water wet and clean surfaces.

Part of the guide: Water & Weather Phenomena →