Preparation of a pure, dry sample of a soluble salt from an insoluble or carbonate, using a Bunsen burner to heat dilute acid and a water bath or electric heater to evaporate the solution. Chemistry 4.4.2.3 Trilogy 5.4.2.3 Synergy 4.7.3.2 AT 2– Safe use of appropriate heating devices and techniques including use of a Bunsen burner and a bath or electric heater. AT 3 – Use of appropriate apparatus and techniques for conducting chemical reactions, including appropriate reagents. AT 4 – Safe use of a of equipment to purify and/or separate chemical mixtures including evaporation, filtration, crystallisation. AT 6 – Safe use and careful handling of liquids and solids, including careful mixing of reagents under controlled conditions. WS 2.3, WS 2.4 Neutralisation (Chemistry only) Spec ref. Skills Determination of the reacting volumes of solutions of a strong acid and a strong alkali by titration. Higher Tier only Determination of the concentration of one of the solutions in mol/dm3 and g/dm3 from the reacting volumes and the known concentration of the other solution. Chemistry 4.4.2.4 AT 1- Use of appropriate apparatus to make and record a range of measurements accurately, including volume of liquids. AT 8 - The determination of concentrations of strong and strong alkalis. MS 1a, MS 1c, MS 2a, WS 2.4, WS 2.6 Electrolysis Spec ref. Skills Investigate what happens when aqueous solutions are electrolysed using inert electrodes. This should be an investigation involvingdeveloping a hypothesis. Chemistry 4.4.3.4 Trilogy 5.4.3.4 Synergy 4.7.5.3 AT 3 - Use of appropriate apparatus and techniques for conducting and monitoring chemical reactions. AT 7 – Use of appropriate apparatus and techniques to draw, set up and use electrochemical for separation and production of elements and compounds. AT 8 - Use of appropriate qualitative reagents and techniques to analyse and identify unknown samples or products including gas tests for hydrogen, oxygen and chlorine (Chemistry only). trial
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.