Make boats that race across water, powered by soap.
ExpeRiment with different liquids to see if they produce the same effect.
Learn how soap affects the way water molecules hold onto each other.
About this activity
Comedian Rufus Hound and his son Alby make soap powered boats and learn how soap affects the way water molecules hold onto each other.
Rufus and Alby do a science magic trick with some pepper (or oregano, if that’s your flavour), washing up liquid and water. Watch the flakes shoot across the water at the touch of a finger. They experiment with different liquids, investigating how substances around the house affect the surface of water. The dramatic effect you see is because the soap weakens the pull that water molecules have on each other. As a result, as the soap spreads over the surface of the water, the water is able to pull away, taking the oregano or pepper with it.
This amazing trick can be used to make a great activity. Cut a boat shape out of a drinks carton, with a little space at the back (for the ‘engine’). When you add a drop of soap in the hole, it pushes water out, backwards. The water moving out the back of the boat pushes it forward, just as hot gases coming out of the bottom of a rocket push it upwards.