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Practicals

Soap Powered Boat
AKA: Foil Boat

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Fig 1: The boat shape
Fig 1

Summary

A simple boat shape is made from foil. A small amount of washing up liquid "powers" the boat forward.

Operation

This can be conducted as a practical or demonstration and although not necessarily part of a syllabus, the principles behind this fun experiment are chemistry based.

Equipment typically required (per set):

  • Aluminium foil
  • Scissors
  • Washing up liquid
  • Large trough or bowl of water
  • Cocktail stick

Firstly a simple boat shape resembling the diagram above needs to be cut from aluminium foil. Try to make the shape symmetrical and ensure that a small square well is cut at the back of the 'boat'. This is where you will be adding the fuel- in this case a small drop of standard washing up liquid.

The bowl or trough needs to be filled with water and the foil boat gently floated on the surface. Use the cocktail stick to collect a small amount of washing up liquid and dab the end of the stick into the well of the boat ensuring contact with the water. While doing this, try not to disturb the position of the boat.

A soapy film of washing up liquid should be seen to spread from the back of the boat which should be sufficient to 'push' the boat along.

The boat behaves in a similar way to an air powered water rocket. With the rocket, air flows out of the bottom, forcing the rocket into the air. With the boat, the soapy liquid emerges from the well of the boat and tries to spread over the surface of the water, pushing the boat along in the process. Once the soapy film has covered the whole surface of the water in the bowl, the boat should stop moving.

A flexcam or webcam could be used to view the flow of soapy film from the back of the boat as this can be hard to see with the naked eye. Shining a lamp at an acute angle onto the surface of the water in the bowl may assist in viewing this.

Safety

 CautionThe contents of this page are for information only. Please refer to CLEAPSS, SSERC or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.