GCSE Chemistry required practical activity: purification Teachers’ notes Required practical activity Apparatus and Techniques Analysis and purification of samples from different sources, AT 2, AT 3, AT 4 including pH, dissolved solids and distillation. Analysis and Distillation of water from different sources Materials In addition to access to general laboratory equipment, each needs: 50 cm3 sample of water’ ‘sea 10 cm3 sample of water’ ‘spring 10 cm3 sample of water’ ‘rain a few ice cubes universal indicator solution or paper. access to balance(s) with resolution to 0.01 g. Technical information Although only a small quantity of water needs to be distilled, enough needs to be present in the flask to avoid it boiling dry and cracking. Ersatz sea water can be produced by dissolving 25 g sodium chloride in 1 dm3 water. The pH will need to be adjusted so that it produces a turquoise colour with universal indicator, indicating a pH of 8.0 8.5. This can be achieved by adding sodium carbonate solution in small volumes and – monitoring with a pH probe until the desired pH is reached. Ersatz spring water can be simulated using 0.1 M magnesium sulfate solution. This should have a pH of 5.5 6.5 and should turn universal indicator yellow-green. – To prepare 0.1 M magnesium sulfate solution, consult CLEAPSS Recipe Book 55.
GCSE Chemistry required practical activity: purification Teachers’ notes Required practical activity Apparatus and Techniques Analysis and purification of samples from different sources, including pH, dissolved solids and distillation. AT 2, AT 3, AT 4 Analysis and Distillation of water from different sources Materials In addition to access to general laboratory equipment, each needs: 50 cm3 sample of ‘sea water’ 10 cm3 sample of ‘spring water’ 10 cm3 sample of ‘rain water’ a few ice cubes universal indicator solution or paper. access to balance(s) with resolution to 0.01 g. Technical information Although only a small quantity of water needs to be distilled, enough needs to be present in the flask to avoid it boiling dry and cracking. Ersatz sea water can be produced by dissolving 25 g sodium chloride in 1 dm3 water. The pH will need to be adjusted so that it produces a turquoise colour with universal indicator, indicating a pH of 8.0 – 8.5. This can be achieved by adding sodium carbonate solution in small volumes and monitoring with a pH probe until the desired pH is reached. Ersatz spring water can be simulated using 0.1 M magnesium sulfate solution. This should have a pH of 5.5 – 6.5 and should turn universal indicator yellow-green. To prepare 0.1 M magnesium sulfate solution, consult CLEAPSS Recipe Book 55.
AQA-8462-PRACTICALS-HB.DOCX