What is surface tension or why can an insect stand on water?

This lesson developed by Reach Out! Recommended Age: Early and Later Elementary


Why can bugs stand on water? What is surface tension?

What you need:

What to do:

  1. Pour 1/2 cup of milk into one of the pie pans.
  2. Drip 4 or 5 drops of each color of food coloring onto the milk. Don't put the drops too close to each other or on top of each. Spread your drops out!
  3. Check it out. What happens?
  4. Carefully drip 4 or 5 drops of liquid dish soap on the milk on the side of the pan.

What is happening?

Certain things can float on water because of a property of liquids called "surface tension." Surface tension causes the surface of liquids to act like a thin, invisible membrane. Water molecules are attracted to each other. This gives water its high surface tension. The high surface tension of water allows items that are more dense than water, such as liquid dish soap, to be suspended on its suface.

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