How to Make Boat Powered by Soap

Using detergent to power a boat is a fun science experiment. You will learn to make a boat that runs only on detergent and find out! How surface tension of water is affected to power your boat.

Required Materials

  • Sheet of cardboard or Styrofoam
  • Liquid dish soap
  • Dropper or Pencil
  • Scissors


  1. Cut a sheet of cardboard into the shape of boat. It should be 2 inch long and 1.5 inch wide and make triangular shaped notch in its back (as shown in the figure).
    Soap Boat
  2. Place your boat in a water tub or in any basin so that your boat have enough space to move.
  3. Place a drop of liquid dish soap in the notch of your boat with dropper or pencil.

Watch your boat going around the tub! It will move forward.

Soap boat in the water


Water molecules are attracted to each other which creates surface tension in the water. Liquid dish soap is a surfactant means it breaks down the surface tension of water. When you add liquid dish soap in the notch, it breaks the surface tension of water contain in the notch, which in turns creates enough force to push the boat forward. Light material (e.g. Styrofoam or cardboard) is used to build the boat so that it can be pushed when surface tension breaks.


  1. Use different materials to build your boat and find out! Which material provides more speed?