Separating sand, sawdust and salt

This session should take 60 minutes. 

Equipment

• 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.