Simulation of Chemical Analysis (Ion Tests)
Chemistry required practical: identifying the ions in an unknown ionic compound.
The simulation is a 3D chemistry bench where pupils work as analysts, running qualitative tests on four unknown salts (Samples A–D) to identify both the metal cation and the negative anion in each, then name the compound.
The five tests available:
- Flame test — a lit blue Bunsen burner; the pupil taps or drags the nichrome wire into the flame and the flame takes the characteristic ion colour (lithium crimson, sodium yellow, potassium lilac, calcium orange-red, copper green). The colour shows only while the wire is in the flame and returns to blue when withdrawn — reinforcing that the colour is emitted light, not a lasting change.
- Sodium hydroxide — a dropper adds NaOH and a coloured precipitate forms: copper blue, iron(II) green, iron(III) brown, and the white precipitates (aluminium, calcium, magnesium), with aluminium correctly redissolving in excess.
- Acid + limewater (carbonate) — a proper sealed setup: the reaction tube is bunged with a delivery tube leading into a second tube of limewater; carbonate samples fizz, and the CO₂ bubbles through the limewater, turning it milky.
- Silver nitrate (halides) — after nitric acid, silver nitrate gives chloride white, bromide cream, iodide yellow.
- Barium chloride (sulfate) — after hydrochloric acid, barium chloride gives a white precipitate for sulfates.
Each test records an observation. Once a pupil has a positive cation result and a positive anion result, an Identify button reveals the conclusion — the cation, the anion, an evidence table, the reasoning, and the salt’s name and formula. The four unknowns (CuSO₄, NaCl, CaCO₃, FeBr₃) between them require every test type, so no single test solves everything. Negative results are handled correctly too (e.g. silver nitrate on a sulfate gives no precipitate), which models real deductive analysis.
The full Adapt accessibility suite is built in: dark navy theme, Irlen colour overlays, reading ruler, dyslexia spacing, text scaling, high contrast, projector mode, colour-blind filters, colour-naming on every result, tap-or-drag interaction, and a buttons-only mode.
Suggested class activity: “The Mystery Salts — Forensic Analysis”
Format: pairs or small groups, ~30–40 minutes. Frame it as a forensic/quality-control scenario: “Four unlabelled containers arrived at the lab with their labels destroyed. Your job is to identify each compound and file a report.”
Setup — give each pupil an analysis grid to complete for all four samples:
| Sample | Flame colour | NaOH result | Acid/limewater | Silver nitrate | Barium chloride | Cation | Anion | Compound + formula |
|---|
Run it in three phases:
- Predict (before touching the sim, ~5 min). Give them the observation-to-ion tables and one worked mystery on paper, so they know which tests reveal cations and which reveal anions. Ask: “What’s the fewest tests you’d need to fully identify one sample?” (Answer: two — one cation test, one anion test — a nice efficiency discussion.)
- Investigate (~20 min). Pupils test all four samples, filling the grid. Encourage a strategy: don’t run all five tests blindly — think about what each result rules in or out. Sample D is deliberately instructive: iron(III) gives no flame colour, so they must switch to the NaOH test — a built-in lesson that a negative result is still evidence.
- Report & justify (~10 min). Each group writes a one-line conclusion per sample with justification: “Sample A is copper sulfate because the flame turned green (Cu²⁺) and barium chloride gave a white precipitate (SO₄²⁻).”
Discussion / extension questions:
- Why must you add dilute acid before silver nitrate or barium chloride? (To remove carbonate ions, which would otherwise give a false precipitate.)
- Why use a blue Bunsen flame, not the yellow safety flame? (The luminous yellow flame would mask the ion colour.)
- Aluminium, calcium and magnesium all give white precipitates with NaOH — how do you tell aluminium apart? (It redissolves in excess.)
- Stretch: instrumental methods (like flame emission spectroscopy) are faster, more accurate, and detect tiny amounts — why might a lab prefer them over these chemical tests?
Adaptation for lower-attaining or SEND pupils: turn on colour-naming and buttons-only mode, and pre-fill the first row of the grid together as a class so the pattern is modelled before they work independently. For a challenge, ask higher-attaining pupils to work out the ionic equations for the precipitate reactions.