Soap-Powered Boat ~ Science Challenge!
Objective: Build a model boat out of foam or cardboard that travels the furthest distance and
the longest time in water when you apply liquid dish soap.
Materials: A foam tray or piece of cardboard, liquid dish soap, a toothpick, and a tub of water.
1. Cut a foam tray or a piece of cardboard into a boat shape. A good size is 2 inches by 2
inches, but you can experiment with smaller or bigger sizes to see if they can move
2. Cut a notch out of the back of your boat as shown in the picture. (See below) You can
experiment with different sizes and shapes of your notch to see what will make your boat
move easier.
3. Dip a toothpick into liquid soap and use the toothpick to put soap onto the inside of the
notch at the back of the boat.
4. Carefully place the boat onto the surface of the water and watch it move across the
water. To test your boat again, take it out of the water, wipe off any soap, and reapply a
new layer of soap.
How does it work? Soap is a surfactant, which means that it breaks down the surface
tension of water. As the surface tension is broken up, it creates enough of a force to push the
lightweight boat across the surface.
Possible other variables to consider: Does warm water work better than cold water? Which
material works better: cardboard or foam? Do certain varieties of liquid soap work better than
Science Challenge: Winners will be determined by how far and how long their boat travels
before it stops.
Project Due: Thursday, November 19th
Class Competition: Friday, November 20th
Finals in Cafeteria: Wednesday, December 2nd