Chemistry Required Practical: Water Purification


- The Method (In Blue)

- Common Mistakes (In Yellow)

- Safety Notes (In Pink)

  • Created by: Hannah
  • Created on: 26-03-19 12:01
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  • Chemistry Required Practical: Water Purification
    • 1. Pour around 1 cm depth of the sea water into a test tube in the rack. Add a few drops of universal indicator solution. Using a pH colour chart, match the colour and record the pH of the water in the results table. Repeat this test for spring water and rain water and record the results.
      • 2. Weigh a dry watch glass. Record its mass in the table. Pour 4cm cubed sea water (less if your watch glass is small) into it and place it above a beaker acting as a water bath.
        • 3. Allow all the water to evaporate from the watch glass. Do not let the water bath boil dry.
          • 4. You should see dissolved solids on the glass. Remove the watch glass with tongs and allow to cool. Dry the bottom of the watch glass with a cloth and reweigh it. Record the new mass in the table.  Subtract the mass of the watch glass alone and record the mass of the dissolved solids. Wash the watch glass and dry it.
            • 5. Repeat steps 2 – 4 for the other water samples. You do not need to weigh the empty watch glass again as long as you use the same one each time. Place the remaining sea water (around 40cm cubed) in the conical flask and set up the apparatus for distillation as shown in the diagram.
              • 6. Make sure the conical flask is held on the tripod and gauze using the clamp stand.  Place a mixture of ice and water in the beaker surrounding the test tube.
                • 7. Heat the sea water with the Bunsen burner until it starts to boil.  Then reduce the heat so that the water boils gently.  Distilled water will collect in the cooled test tube. Collect about 5 cm depth of water in this way, then stop heating.
                  • 8. Repeat the tests in steps 1 to 4 again using the distilled sea water, again recording your results in the table.
    • Wear eye protection at all times.
    • When adding drops of universal indicator, add one or two drops. Too much universal indicator makes the colour hard to identify.


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