A blank nine-step write-up with the correct table headings. Print it for a real lesson and fill it in by hand. See the specimen lab book
Blank write-up: Water purification
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Study Hack Lab
RP 8 · Chemistry
Water purification
Write-up template
Name
Date
Course
GCSE Chemistry
Board and specification
AQA GCSE Chemistry (8462), 4.10.1.2AQA GCSE Combined Science: Trilogy (8464), 5.10.1.2Apparatus and techniques: AT 2, AT 3, AT 4
Class and teacher
Aim
Analyse water from four sources (pH and dissolved solids), then purify sea water by distillation and test the sea water and the distilled water for sodium and chloride ions.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
Water from rivers, the sea and the ground carries dissolved salts. Evaporating a measured volume and weighing what is left gives the mass of dissolved solids; heating to constant mass makes sure every trace of water has gone. Distillation purifies water: it boils off, the vapour condenses in the cold condenser, and the salts stay behind. A flame test (sodium: yellow) and silver nitrate with nitric acid (chloride: white precipitate) check the water before and after.
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
Variables
Independent (you change)
Dependent (you measure)
Control (you keep the same)
Prediction
Which water will leave the most solid behind when it is evaporated?
What will the pH of the sea water be?
You distil the sea water and test the distilled water. What will the tests show?
Risk assessment
Hazard
Harm it could cause
Control
2 Apparatus
Eye protection (goggles) Protects the eyes from spitting solid, hot water and splashes.
Water samples: tap, sea, bottled mineral and river water The water from different sources.
Test tubes in a rack, and a white tile Small samples for the pH and ion tests.
Universal indicator solution and colour chart Shows the pH of each sample as a colour.
pH meter and pH 7 buffer (resolution 0.01) Measures pH to 0.01 (if you choose it).
Top-pan balance (0.01 g) (resolution 0.01 g) Weighs the basins before and after evaporating.
Four evaporating basins (A–D) Hold each sample while the water evaporates.
Measuring cylinders: 25 cm³ and 250 cm³ (resolution 0.5 cm³ and 2 cm³) Measure the volume of each sample.
Water bath (beaker on a tripod and gauze), Bunsen burners and heatproof mats Evaporates the water gently.
Side-arm (distillation) flask, anti-bumping granules Holds the sea water while it boils.
Liebig condenser, retort stands and clamps, rubber tubing Cools the steam so it condenses into pure water.
Thermometer, −10 to 110 °C (resolution 1 °C divisions (read to 0.5 °C)) Measures the temperature of the vapour at the side arm.
25 cm³ measuring cylinder (receiver) (resolution 0.5 cm³) Collects and measures the distillate.
Nichrome wire loop in a handle For the flame test for sodium ions.
Dilute nitric acid (0.4 mol/dm³), silver nitrate solution (0.05 mol/dm³) and dilute hydrochloric acid Nitric acid and silver nitrate test for chloride ions; the hydrochloric acid cleans the flame-test wire.
3 Method
Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.
4 Results
The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.
pH of each water sample · Universal indicator, matched to the colour chart.
Water sample
Colour of universal indicator
pH
Tap water
Sea water
Bottled mineral water
River water
Evaporating to constant mass · Basins A–C: 25.0 cm³ of sea water each. Basin D: 250 cm³ of bottled mineral water. A dash means the mass was already constant.
Basin
Volume of water in cm³
Mass of empty basin in g
Mass after first heating in g
Mass after heating 2 in g
Mass after heating 3 in g
Mass of dissolved solids in g
Dissolved solids in g/dm³
A (sea)
B (sea)
C (sea)
D (mineral)
Mean (sea)
Distilling the sea water · 100 cm³ of sea water; distillate collected for 10 minutes in a 25 cm³ measuring cylinder.
Distilled
Temperature of the vapour in °C
Volume of distillate in cm³
Sea water
Testing for ions · Flame test with a nichrome wire loop; a few drops of dilute nitric acid, then silver nitrate solution.
Water
Flame colour
With silver nitrate
Sea water
Distilled water
Anomalies
Ring any anomalous result. Say what probably went wrong and whether you repeated it.
5 Graph
pH of each water · Draw a bar chart. Water sample goes along the bottom.
6 Analysis
Mass of solid in basin A
mass of solid = mass of basin and solid − mass of empty basin
Answer
Dissolved solids in basin A
dissolved solids (g/dm³) = mass of solid (g) ÷ volume of water (dm³)
Answer
Mean dissolved solids in sea water
mean = sum of the results kept ÷ number of results kept
Answer
Dissolved solids in the mineral water
dissolved solids (g/dm³) = mass of solid (g) ÷ volume of water (dm³)
Answer
Which ions are there?
Answer
7 Conclusion and evaluation
Conclusion
Conclusion: what do your results show? Use your own numbers.
Sources of error
For each, say whether it is systematic or random, and how it affected your results.
Not heating to constant mass
Solid spitting out of the basin as the last water boils off
The resolution of the balance (0.01 g) compared with the mass of solid from the mineral water
Judging the colour of universal indicator by eye
Boiling the flask too hard during distillation
The thermometer bulb down in the boiling liquid instead of level with the side arm
Cooling water in at the top of the condenser
A dirty flame-test wire
Improvement
How could you improve the method? Say why it would help.
8 Make safe and clear up
Turn off the Bunsen burners, then the condenser water; leave the flask, basins and tripods to cool on the heatproof mats
Pour the silver nitrate mixtures into the residue bottle, and the other solutions down the sink with plenty of water
Soak the salt crust out of the basins in warm water, and rinse the flask, test tubes and cylinders
Wash your hands (the river water may carry microbes), then take off your goggles last