Saturday, 15 January 2011


How can you get salt from a rock salt or seawater? This is a simple classroom demo to show that the common salt in the kitchen is mined from underground or can be taken out from the seawater.
You may use either rock salt or seawater (which ever is readily available in your school).


  • Rock salt ( or seawater)
  • Mortar and pestle
  • 2 x 250 ml beaker
  • evaporating basin
  • tripod
  • bunsen burner
  • gauze
  • heatproof mat
  • goggles ( or any eye protection)
  • stirring rod
  • filter paper
  • funnel
  1. Crush some rock salt using mortar and pestle. (If using seawater, proceed to procedure c right away)
  2. Put crushed rock into a 250 ml beaker and add enough water, and stir the mixture well.
  3. Using the funnel, filter paper, and another 250ml beaker, filter the mixture or seawater. The water that comes out through the filter paper should be clear.
  4. Put some of the filtered liquid into the evaporating basin and heat it.  Turn off the Bunsen burner when crystals start to form around the edges of the solution and let the water evaporate without heating.  Be careful because the salt will start spitting out of the basin.
  5. The white crystals or powder left in the evaporating basin is called a pure salt.
  1. Describe the process of obtaining pure salt from rock salt or seawater.
  2. Why didn’t filtering remove the salt from the water?
  3. Plan an activity that could collect the water rather than the salt.

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