This process is often used to give students a start in understanding simple separation processes. A mixture of sand and salt is made up before the lesson. Pupils are to separate the mixture using filtration and evaporation.
Equipment required (one set):
- Medium beaker
- Bunsen burner
- Glass rod (to stir)
- Evaporating basin
- Filter paper and medium funnel
- Salt and sand mixture
- Conical flask
The salt and sand mixture should be prepared beforehand using around 20% salt and 80% sand.
Students firstly mix some of the sand/salt mix in about 50cm³ of water in a beaker. It is then heated gently whilst being stirred with the glass rod. The mixture should then be filtered through the filter paper and funnel into the conical flask. The filtrate (what goes through the filter paper) should be poured into an evaporating basin and carefully heated until it starts to 'spit' The remaining damp salt should be left to dry on a windowsill. If time is not a problem, the solution can simple be left on a windowsill for a couple of days to evaporate naturally leaving salt crystals.
The remaining sand and water mixture can be left, allowing the water to evaporate, leaving the sand to return to its original dry state.