Break the tension to make your fish swim! A surface tension experiment.
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Monster Sciences Experiment about Liquids: Surface tension – Fast Fish
What you will need:
- A large bowl with water in it
- A piece of paper or cardboard
- Liquid soap
What you will do:
- Put the bowl on a flat surface and fill it with water.
- Cut out a fish from a piece of paper or better yet cardboard, Make sure your fish has a nice v in its tail.
- Carefully lay the fish down on the surface of the water near one side of the bowl. Now rub a little liquid soap onto your finger and then gently touch the water behind the fish. Just touch it once and take your finger away, then watch what happens.
What is going on?
The water in the bowl has surface tension, which keeps the fish on top of the water. Soap, however, breaks the surface tension by breaking the attraction between the water molecules, so the water behind the fish “relaxes”. The surface tension still exists in front of the fish, so the water molecules in front of the fish are still pulling towards each other, and they pull the fish too.
Monster Challenges
- Try floating a cork in he middle of a fresh bowl of water. What happens? Now add a drop of soap. Can you explain the change based on what you have learned in this experiment? Can you use this idea to have paper boat races?
- Research how and why surface tension is broken to clean up oil spills at sea.
Get this experiment here or as part of a bundle of Surface Tension Experiments here.
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