Investigating chemical species in a sample (internal)
Internal 3 credits Qualitative analysis Precipitation Flame tests Solubility rules SignificanceAS 91911, 3 credits. A qualitative investigation into which chemical species are present — via EITHER an ionic identification procedure OR an organic functional-group procedure. Every grade requires linking to the compound present AND stating the species' significance for people and/or the environment — a component easy to leave out entirely.
1 Reading the notation
Two identification pathways (ionic OR organic), and a significance requirement present at every grade.📖 Terms the schedule grades you on
5 terms- Carry out (Achieved)
- Primary data, identification, LINK to compound present, describe significance.
- In-depth (Merit)
- Explain identification via primary data; equations for ALL changes; explain significance.
- Comprehensive (Excellence)
- Justify identification via SECONDARY DATA and principles; discuss significance.
- Identification procedure
- IONIC (solubility rules, complex ions) OR ORGANIC (functional group reactions).
- Secondary data
- Solubility rules/complex ion formulae, a functional group reaction map, or scientific literature.
2 Ionic identification
Solubility rules, flame tests, and precipitation equations with state symbols.| Test | Positive observation | Inference |
|---|---|---|
| Flame test | Characteristic colour | Metal cation present |
| Dilute acid added | Effervescence; limewater goes milky | Carbonate |
| Acidified AgNO₃ | White / cream / yellow precipitate | Cl⁻ / Br⁻ / I⁻ |
| Acidified BaCl₂ | White precipitate | Sulfate |
| NaOH added, warmed | Pungent gas, damp red litmus turns blue | Ammonium |
| NaOH added dropwise | Coloured precipitate, may redissolve in excess | Transition metal cation |
Write the ionic equation with state symbols for every positive. The standard names the use of chemistry symbols and conventions as an assessed requirement.
3 Testing systematically
Observation, inference, equation — and eliminate as you go, for either pathway. ✕Reporting only positive results
A report listing only "tests that worked" hides half the reasoning the standard assesses. A negative result — no reaction with acidified silver nitrate — eliminates specific possibilities just as legitimately as a positive result confirms one.4 Significance for people and the environment
Required at every grade, and easy to leave out entirely.What a strong significance statement includes
- The specific species identified — not a generic category.
- The specific mechanism or effect (health, environmental, regulatory).
- Who or what is affected.
- A real-world consequence — a limit, a use, a risk.
Practice
Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.
Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.
Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.
Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.