Diving Fish

7-10 year olds | half hour

Learn about the properties of surface tension using a fun fish activity. Surface tension is when molecules cling to each other tightly. Think of bricks making a big house. Most of the bricks have bricks on top of them. However, the top layer of bricks doesn’t have anything on top of them. When molecules don’t have anything on top of them, they cling together tightly (or are more attracted to one another), producing surface tension.

What You'll Need

  • a bowl
  • washing-up liquid
  • cardboard
  • pen
  • scissors


1. Trace a fish shape on a small piece of cardboard. Cut out with scissors.
2. Fill the bowl with water to the very top, making sure not to spill over.
3. Place the fish on the surface, so that it is floating. Surface tension at the top of water allows small things like cardboard to float.
4. Now, drop a bit of washin up liquid in the middle of the bowl.
5. Watch the fish zoom across the surface of the water! The fish moves because washing-up liquid breaks down and weakens the surface tension.

Tags: science

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