A bit of chemistry that all gravy, move an Oxo cube as fast as possible
Make sure you know which side of your table is buttered as you create a slick surface for your swift stock cube.
It is suggested that either:
An entire morning be devoted to the problem (e.g. on the last day of term), which would allow 2 h for practical activities and 30 minutes for judging
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.
- Items from the junk list to encourage creativity
- The judges will require a stop watch or an arrangement with a computer and photocells if the Oxo cubes move too fast.
Materials per group
- Sodium hydrogencarbonate (maximum amount = 3 level teaspoons)
- citric acid (maximum amount = 9 level teaspoons)
- Access to water
- Butter/margarine to reduce friction
Equipment per group
- Identical teaspoons (can be plastic)
- Safety glasses.
Health, safety and technical notes
- Read our standard health and safety guidance here.
- Wear eye protection.
- This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete.
- For more information on sodium hydrogencarbonate see CLEAPSS Hazcard HC095a.
- Citric acid is an eye irritant, see CLEAPSS Hazcard HC036c.
Some guidance may be needed for younger age groups – e.g. water is needed for the reaction. The reaction might be used to do the moving, or it could be used to start the movement – e.g. to trigger movement of a counterbalance
To increase the chemical content, the task could be extended by prior (or subsequent) experimentation, to select the best choice of gases/chemicals.
This resource is part of a collection of problem-solving activities, designed to engage learners in small group work. Find out how to use these resources, and obtain a list of suggested ‘junk items’ here.
The resources were originally published in the book In Search of More Solutions.
This experiment was based on an idea contributed by Peter Borrows.