Chemistry is a superpower, and using a few junk items learners can lift and move heavy objects

Design and make an apparatus that can move the heaviest object in this fun classroom competition. 


It is suggested that either: an entire morning be devoted to the problem (e.g. on the last day of term), which would allow two hours for practical activities and 30 minutes for judging


The problem be given to the class as a homework exercise two 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 judges will require a stop watch.

Materials per group

  • Sodium hydrogencarbonate (maximum amount = 3 level teaspoons)
  • Citric acid (maximum amount = 9 level teaspoons) (Eye Irritant.)
  • Access to water
  • Butter/margarine to reduce friction

Equipment per group

  • Items from the junk list to encourage creativity 
  • 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.


During trialling, guidance needed to be given to younger age groups to say that 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.