Required practical: Water Purification
What the simulation does
The simulation models the AQA GCSE required practical “Analysis and purification of water”. Pupils work through three stages on three unknown water samples — A (distilled), B (tap), C (sea water) — and build up evidence to decide which are pure and how to purify the impure ones.
Stage 1 — pH test. Pupils drag (or tap) a dropper to add universal indicator to the water, and read the colour off a pH scale that appears along the bottom, which points an arrow at the measured value.
Stage 2 — Evaporation. A measured 25 cm³ is heated in an evaporating basin over a Bunsen. Pupils watch the blue water boil, steam off, and dry out completely — leaving nothing for distilled water, a faint ring for tap water, and a thick white salt crust for sea water. This shows the mass of dissolved solids each source contains.
Stage 3 — Distillation. Using the ice-and-water condensing setup, the water is boiled in a conical flask; a thermometer climbs to 100 °C and holds; vapour travels along a delivery tube and condenses in a boiling tube standing in ice and water; pure distillate drips in and collects. This demonstrates that distillation keeps the water and leaves the solids behind.
A conclusion screen then compiles the evidence into a results table and explains why distillation produces pure water. The full ClassAdapt accessibility suite is built in (light/high-contrast default, dark toggle, text scaling, reading ruler, colour-naming, buttons-only mode, reduce/slow motion, colour-vision filters).
Suggested class activity
“Which water is which? — A forensic water investigation” (single lesson, works as a whole-class projector task or on pupils’ own devices)
Frame it as a mystery: pupils are lab technicians given three unlabelled water samples and must identify each source and recommend how to make it drinkable.
Give each pupil a simple results table to complete:
| Sample | pH | Solids left on evaporation | Distillate pure? | Identity | Pure or needs treatment? |
|---|
Run it in three phases:
- Predict — before testing, pupils predict what each sample will do and why (retrieval of solubility/dissolved solids ideas).
- Test and record — pupils run all three stages on each sample, filling in the table. Encourage them to note the observation and the inference separately (e.g. “white crust → dissolved solids present”).
- Conclude and evaluate — pupils write two or three sentences answering: Why does evaporation lose the water but distillation keep it? and Why is distillation not used to make all our tap water? (links to the energy-cost/desalination point in the conclusion screen).
Extension / stretch: ask pupils to design the cheapest sensible treatment for each sample and justify it, or to explain why the acid-free anion tests they’ve met elsewhere wouldn’t tell them whether water is “pure.”
Adaptation built in: lower-attaining or SEND pupils can use buttons-only mode and the colour-naming option and complete a partially-filled table; stretch pupils tackle the evaluation questions and the cost-reasoning extension.