Learning Aims:
  • To differentiate between solutions and mixtures
  • To recognize the importance of different solubilities
  • To identify possibilities of recovering salts from solutions
Salt, water, dirt, beaker
Suggestions for use:

Tell the students that you have spilled your salt on the floor where it has mixed with small dirt particles and other impurities on the floor. Ask the students to come up with an experiment using the idea of sieves to obtain a pure sample of salt from the mixture. Advise students to think about the previous activities when devising their experiment. Students should use the idea from the coffee filter that if the salt is dissolved in the water is can fit through the filter paper and the water can then be evaporated off.

Possible questions:
  • Why can you not separate salt from dirt using a sieve (without water)?
  • Why can you not separate salt from water using a filter paper?
  • What other techniques could you use to regain the salt from the water