Chemistry · 12.5 Identification of ions · Paper 5/6 practical
Flame Tests. Colour the fire.
Clean a nichrome wire in concentrated hydrochloric acid, dip it in the sample, and hold it in a roaring blue Bunsen flame. Each metal cation gives a characteristic flame colour — use it to identify the metal ion present.
0620 Topic 12.5 — Flame tests
Li · Na · K · Ca · Ba · Cu
Paper 5/6 — Practical
no sample
wire dirty
Clean the wire between samples so the previous ion does not contaminate the next test.
Sample
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Flame colour reference — 0620 syllabus
Observation log
Hold a sample in the flame to log an observation.
📋 Method (Cambridge practical procedure)
- Dip a clean nichrome (or platinum) wire into concentrated hydrochloric acid, then hold it in a hot Bunsen flame until there is no colour — this cleans it.
- Dip the clean wire into the concentrated acid again, then into the solid sample so a little sticks to it.
- Hold the wire at the edge of a roaring (blue) flame and observe the colour given to the flame.
- Compare the colour with known results to identify the metal ion.
- Clean the wire again before testing the next sample.
⚠ Sources of error & precautions
- Contamination — sodium's strong yellow colour easily masks others; always clean the wire thoroughly between tests.
- Use a roaring (blue) flame, not a yellow safety flame, which has its own colour.
- Use a nichrome or platinum wire — they do not give their own flame colour.
- Concentrated HCl is corrosive — wear eye protection and avoid skin contact.
- View the colour against a dark background for clarity.
🎯 Syllabus reference (0620)
- 12.5 Identification of ions and gases — describe the use of a flame test to identify the cations Li⁺ (red), Na⁺ (yellow), K⁺ (lilac), Ca²⁺ (orange-red), Ba²⁺ (light green) and Cu²⁺ (blue-green).