Help Mrs Johal to clean up after her messy class by separating sand, sawdust and salt

This session should take 60 minutes. 


  • Filter funnels
  • Filter papers
  • Hand lens
  • Tweezers
  • Sieve
  • Mixture of sand/salt/sawdust 
  • Water

Health, safety and technical notes

  • Read our standard health and safety guidance here.
  • Wear eye or clothing protection if desired.
  • This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete. 
  • There are no significant hazards associated with this experiment.

Possible approaches

Questions to ask students who need help are:

  1. Do you think magnets should work?
  2. What about a sieve?
  3. A home-made sieve?
  4. Could you use tweezers and a hand lens to pick out the pieces?
  5. What about using water? – Floaters/sinkers, dissolving.

Few students realise that only a small amount of water is needed to dissolve the salt. If a large amount of water is used, it can take a long time to evaporate.

The final drying of the salt and the sand can be done in an oven.

Possible extension

Students could design a large scale separation plant that works continuously. Separate chocolate bits from chocolate chip cookies.