This topic summary covers Knowledge Organiser: Flame Tests within Flame Tests for GCSE Chemistry. Revise Flame Tests in Chemical Analysis for GCSE Chemistry with 22 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Flame Tests
Flame Colours
- Li⁺ = Crimson red
- Na⁺ = Orange-yellow
- K⁺ = Lilac/purple
- Ca²⁺ = Orange-red (brick red)
- Cu²⁺ = Blue-green
- Ba²⁺ = Yellow-green (apple green)
Method Steps
- Dip wire in dilute HCl
- Heat until no colour
- Dip in HCl then sample
- Hold in blue flame
- Observe colour immediately
Science Behind It
- Heat excites electrons to higher levels
- Electrons fall back to ground state
- Energy released as coloured light
- Each element has unique energy gaps → unique colour
Limitations
- Not all metals give colours
- Similar colours can be confused
- Sodium contamination common
- Blue glass needed for potassium
Key Equations
- No calculation equations — identification topic
- Li⁺ = crimson, Na⁺ = orange-yellow, K⁺ = lilac, Ca²⁺ = orange-red, Cu²⁺ = blue-green
- Mnemonic: Little Naughty Kids Can Be (Li Na K Ca Ba — in colour order)
Common Mistakes
- Confusing calcium and sodium flame colours: Calcium = orange-red (brick red); sodium = orange-yellow — they look similar but the yellow is much brighter for sodium
- Forgetting to clean the wire between tests: The wire must be cleaned with dilute HCl and heated until no colour appears — old sample contamination gives false results
- Saying potassium gives a purple flame: Potassium gives LILAC — it is a pale purple/violet; a strong purple is not the correct observation
- Thinking flame tests identify the anion: Flame tests only identify METAL CATIONS — they give no information about the anion (e.g. Cl⁻, SO₄²⁻)
Practice questions for Flame Tests
Which type of wire is used to carry out a flame test?
Explain why different metal ions produce different colours in flame tests.
Quick recall flashcards
What is a flame test?
A test used to identify metal ions by observing the characteristic flame color they produce when heated in a Bunsen burner flame
Flame color for sodium ions (Na⁺)?
ORANGE/YELLOW - persistent yellow-orange flame, very intense and bright