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Separating common salt and sand

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A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

The aim of this activity is to separate a mixture of salt and sand. The method uses the difference in solubility of the two solids and the technique of filtration. You should obtain samples of both as separate solids.

Method:
1. Transfer the salt and sand mixture into the beaker and add distilled water.
2. Place the beaker on the tripod and gauze. Heat gently, while stirring the mixture with the glass rod.
3. Stop heating when the water is about to boil. Turn off the Bunsen burner. Keep stirring for about 1 minute and then leave the beaker to cool.
4. Fold the filter paper and assemble the filter paper on a conical flask.
5. When the beaker is cool enough to handle safely, filter the mixture and collect the filtrate in the conical flask.
6. Move the filter funnel to another conical flask and wash the sand in the filter funnel with distilled water.
7. Place the open filter paper and sand on a paper towel and leave it to dry.
8. Pour the filtrate into the evaporating basin and heat it to evaporate most of the water.
9. Stop heating and allow the concentrated solution to cool down slowly. Crystals of salt will form.
Questions
1. What is the chemical name for common salt?
2. Other salts such as magnesium sulfate can be present as impurities in common salt. Would the separation method used here remove this type of impurity? Explain your answer.
3. What method could you use to find out if your sample of salt was pure? How would the fact that it might be impure show itself?

Solutions
  • Show Solutions
    1. Sodium Chloride
    2. No. Magnesium Sulfate is soluble and so would be present in the filtrate too.
    3. Find the melting point of the solid. If it was impure, the melting point would be lower and not as precise/sharp.



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