Science Experiment: Surface Tension – Pepper Scatter

Science Experiment: Surface Tension – Pepper Scatter

WaterThe surface layer of liquids has a thin elastic “skin” called surface tension. You can see surface tension at work when you see a drop of water – it creates a little “bead” of water, like a little dome. Surface tension is what makes the dome shape – the water doesn’t flatten out. See the drops of water on that leaf? Water is made up of two kinds of atoms, hydrogen and oxygen. The name for the water molecule is H2O. The water molecule has 2 hydrogen atoms represented by the H2 and 1 oxygen atom represented by the O.

Water molecules are attracted to each other because hydrogen atoms and oxygen atoms are attracted to each other. They hug close together really tight. They hug so close together they don’t want to touch other molecules around them. In the picture you can see that the water drops have formed into balls so that they are touching the smallest amount of leaf possible. Try the following experiment to see surface tension at work.

What You Need:

  • bowl
  • water
  • pepper
  • toothpicks
  • dish soap

Fill the bowl with water. Sprinkle some pepper on top of the water – see how it just sits there on top of the water? The pepper is resting on that thin “skin” of surface tension. You can also try this with toothpicks – the toothpicks will also just sit on top of the water resting on the thin “skin” of surface tension.

No put a few drops of dish soap in the water with the pepper. What happens? Soap molecules are different than water molecules. Soap molecules DON’T stick together and they DON’T stick to the water molecule. One part of the soap molecule is attracted to water and the other part wants to push water away – that’s what makes the pepper, or the toothpicks, scatter. The soap breaks the surface tension that water has, it breaks those bonds between the water molecules. The books, websites and science experiments suggestions on this page will help you do research and answer homework questions about surface tension.

Here is a fascinating video from space that demonstrates surface tension:

Websites, Activities & Printables:

Science in Context: Surface Tension is a database you can use in any IndyPL Library Branch or at home. Login using your IndyPL library card number. The Science in Context database will show you articles, images and videos to help you learn about surface tension.​



You can also ask a math and science expert for homework help by calling the Ask Rose Homework Hotline. They provide FREE math and science homework help to Indiana students in grades 6-12.


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9 Responses »

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