Race a Speedboat - p.26

Make a boat "race" across water, just by touching the surface of the water. This happens because there is a force present, called "surface tension."

For the experiment you will need:
-A large, clean plastic bowl of water.
-A colored card - the book suggests paper, but I used a plastic folder divider.
-Scissors
-Dishwashing liquid



1. You draw the shape of your boat on the colored card (any shape will do). Then you cut it out.

*It would be best for young students to draw the shape first, but I just cut out a simple triangle.*



2. Place your boat on the water and let it float. Carefully place it into position.



3. Squeeze a drop of dishwashing liquid onto your finger.



4. Dip your finger in the water, just behind the boat. The boat will shoot forward across the bowl. *You may need to turn volume up*



The dishwashing liquid weakens the surface tension behind the boat. It works because the soap gives off an oily film that rushes outwards, breaking down the surface tension of the water. The surface tension is stronger in front of the boat and causes the boat to pull forward.

Mini Lesson time!