Flame Test – IGCSE Chemistry Definition
IGCSE Chemistry definition of flame test: identifying metal ions by the colour they produce in a flame. Covers colours for Li, Na, K, Ca, Cu and exam tips for 0620.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Flame tests are tested on Paper 6 (practical) and as part of qualitative analysis on Paper 4. You must memorise the colours for five metal ions — this is pure recall, but it is free marks if you know them.
The 0620 definition
A flame test is a qualitative analytical method used to identify certain metal ions by the characteristic colour they produce when heated in a flame.
The colours you must know
| Metal ion | Symbol | Flame colour |
|---|---|---|
| Lithium | Li⁺ | Crimson / red |
| Sodium | Na⁺ | Yellow / golden yellow |
| Potassium | K⁺ | Lilac / purple |
| Calcium | Ca²⁺ | Orange-red / brick red |
| Copper | Cu²⁺ | Blue-green / green |
The method
- Clean a nichrome (or platinum) wire loop by dipping in concentrated HCl and holding in a blue Bunsen flame
- Repeat until the wire produces no colour in the flame (it is clean)
- Dip the clean wire into concentrated HCl again
- Dip the wet wire into the solid sample (a small amount sticks to the wire)
- Hold the wire in the blue (roaring) Bunsen flame
- Observe and record the flame colour
Why use a blue flame?
The blue flame from an open air hole is chosen because it is nearly colourless. A yellow safety flame would mask the colours produced by the metal ions.
Limitations of flame tests
- Sodium contamination: sodium produces a very strong yellow colour that can mask other colours. Even fingerprints contain enough sodium to give a yellow flame.
- Only works for a few metal ions — many metals do not produce distinctive flame colours.
- Cannot distinguish between two metals present in the same sample very easily.
For identifying transition metal ions more reliably, use precipitate tests with sodium hydroxide solution.
Worked exam question
A student carries out a flame test on an unknown compound and observes a lilac flame. (a) Identify the metal ion present. [1] (b) State one precaution the student should take to ensure reliable results. [1]
Mark scheme
(a) Potassium / K⁺ [1]
(b) Clean the wire (in HCl) before testing / use a blue Bunsen flame / ensure the wire gives no colour before dipping into the sample [1]
Common exam mistakes
- Confusing calcium (orange-red) with lithium (crimson red) — calcium is more orange, lithium is deeper red.
- Saying the flame colour for copper is “blue” only — it is blue-green or green. The examiner accepts both, but “blue” alone may not score.
- Forgetting to clean the wire — contamination is the most common source of error in flame tests.
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