Building a chemically powered boat

The boat needs to be propelled by a chemical reaction, and the winner is the boat that travels the furthest.

Time

It is suggested that either:

An entire morning be devoted to the problem (eg on the last day of term), which would allow 2 hours for practical activities and 30 minutes for judging.

Or

The problem be given to the class as a homework exercise 2 weeks or so before the judging. Judging could then take place in a normal double science lesson, allowing 45 minutes for repair and final adjustments, and 30 minutes for judging. (The exercise is better as a pre-set problem for younger students.) 

Equipment

• Eye protection
• ‘Junk’ items
• A testing tank: depends on what is available in your laboratory. However, the type of tank will determine how you evaluate the distance travelled by the boats (see possible approaches below).
• Identical teaspoons (can be plastic).
• Sodium hydrogencarbonate (maximum amount = 3 level teaspoons)
• Citric acid (maximum amount = 9 level teaspoons)
• Access to water

Health, safety and technical notes

• Read our standard health and safety guidance here.
• Wear eye protection. 
• Wear lab coat, or apron if desired. 
• This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete. 
• Citric acid is an eye irritant, see CLEAPSS Hazcard HC036c.

Possible approaches

A suitable long tank may be constructed from stout cardboard, lined with heavy-duty polythene, or by using plastic guttering.

The distance each boat travels can then be measured. Alternatively, a plastic washing-up bowl could be used. A clamp stand is placed in the centre of the bowl and the boat attached to the clamp stand by a piece of cotton, so that it is free to sail round the bowl.

The number of times the boat goes round the clamp stand is then measured. In summer months, you could use a children’s paddling pool as an outdoor testing tank. (Some students will do some re-designing when they realise that in a washing up bowl, the biggest boat is not the best!)

“A good exercise with wide access across the age range”.

Younger age groups may need guidance about why water is needed for the reaction. The fuel could be carried on the boat, or gas could be generated separately and stored in a balloon. 

Possible extension

To increase the chemical content, the task could be extended by prior (or subsequent) experimentation, to select the best choice of gases/chemicals.