Common mistakes students make (and how to avoid them!)
✅ This topic comes up almost every year in Paper 3 (Practical). Learn it well!
❓ What Is a Flame Test?
A flame test is a qualitative test used to identify the metal ion (cation) in a compound. When a metal compound is placed in a hot flame, the metal ion produces a characteristic colour. Different metals give different colours — like a fingerprint!
💡 "Qualitative" means we are identifying what is there — not measuring how much.
⚛️ Why Do Flames Glow Different Colours?
When a metal compound is heated, the electrons in the metal atoms absorb energy and jump to a higher energy level. When they fall back down to their original level, they release that energy as light. Different metals release different amounts of energy, giving different colours.
🔑 Key idea: Different metals → Different energy → Different colour of light
You do not need to explain this in detail for O-Level — just know it happens!
🎨 The 6 Flame Colours You MUST Know
Click each element to see its flame colour!
Li⁺
Lithium
Crimson Red
Na⁺
Sodium
Yellow / Orange
K⁺
Potassium
Lilac
Ca²⁺
Calcium
Brick Red / Orange-Red
Cu²⁺
Copper
Blue-Green
Ba²⁺
Barium
Pale Green
📋 Quick Reference Table
Metal Ion
Symbol
Flame Colour
Lithium
Li⁺
Crimson Red
Sodium
Na⁺
Yellow / Orange-yellow
Potassium
K⁺
Lilac (violet)
Calcium
Ca²⁺
Brick Red / Orange-red
Copper
Cu²⁺
Blue-Green (turquoise)
Barium
Ba²⁺
Pale / Apple Green
⚠️ Sodium's yellow flame is so strong it can mask other colours. Always clean the wire thoroughly!
🔬 Which Ion Are We Identifying?
Remember: the flame test identifies the METAL ION (cation), NOT the anion.
e.g. Both NaCl and Na₂SO₄ give a yellow flame — because both contain Na⁺ ions.
The negative ion (Cl⁻ or SO₄²⁻) does not affect the flame colour.
🧪 Flame Test Simulator
Choose a metal compound to see the flame colour!
← Choose a metal to test
💡 In the real lab: dip your wire, hold it in the flame, and observe the colour immediately!
🥼 How to Perform a Flame Test (Practical Paper 3)
Follow these steps exactly as you would in the exam!
Obtain a nichrome (platinum) wire loop
A nichrome wire is used because it does not burn or colour the flame itself.
Clean the wire
Dip the wire in dilute hydrochloric acid (HCl), then hold it in the Bunsen burner flame. Repeat until you see no colour in the flame.
Pick up the sample
Dip the clean wire into the solid sample (or solution) so a small amount sticks to the loop.
Hold in the flame
Place the loop into the hottest part of the Bunsen burner flame (just above the blue inner cone).
Observe and record the colour
Look at the flame colour immediately. Write down exactly what colour you see.
Identify the metal ion
Compare your observed colour to the table of flame colours to identify the metal ion present.
⚗️ Equipment You Need
🔩 Nichrome wire loop (or platinum wire)
🧪 Dilute hydrochloric acid (HCl) – for cleaning
🔵 Bunsen burner connected to gas supply
🧫 Watch glass or ceramic tile (to hold the sample)
👀 Your eyes! (Optionally: cobalt blue glass for potassium)
🔵 Use cobalt blue glass when testing for potassium — it filters out yellow sodium so you can see the lilac more clearly!
❌ Common Mistakes to Avoid
✗ Not cleaning the wire properly — sodium contamination gives a yellow flame even if sodium is not present!
✗ Using too much sample — makes the colour harder to see clearly.
✗ Wrong part of the flame — use the hottest part, above the blue cone.
✗ Saying "blue" for potassium — it's LILAC, not blue!
✗ Confusing lithium and calcium — lithium is crimson-red; calcium is brick-red/orange-red.
✍️ How to Write Your Answer in Exams
Example Question: A flame test was performed on compound X. A brick-red flame was observed. Identify the metal ion present.
Model Answer: The metal ion present is calcium, Ca²⁺. The brick-red flame indicates the presence of Ca²⁺ ions.
💡 Always name the metal AND write its ionic symbol with the correct charge (e.g. Ca²⁺, Na⁺).
🧠 Memory Tips & Mnemonics
Struggling to remember the colours? Use these tricks!
📖 Colour Story Method
Imagine you're watching a fireworks show:
🔴 Little Lions look Crimson (Li = Crimson Red)
🟡 Naughty Napoleon wore Yellow (Na = Yellow)
🟣 King Kong likes Lilac (K = Lilac)
🧱 Cats Carry Bricks (Ca = Brick Red)
🟢 Cupid has Blue-Green arrows (Cu = Blue-Green)
🌿 Bananas go Pale Green (Ba = Pale Green)
🔠 The "LNKCCB" Order
Li Na K Ca Cu Ba
Li = Crimson
Na = Yellow
K = Lilac
Ca = Brick Red
Cu = Blue-Green
Ba = Pale Green
Sentence: "Little Nancy Keeps Carrying Big Bags"
🩺 Spot the Difference: The Tricky Pairs
Lithium (Li⁺)
Crimson red — deeper, more purple-ish red. Like dark red blood.
Calcium (Ca²⁺)
Brick red — more orange-ish red. Like the colour of a brick!
Potassium (K⁺)
Lilac — a soft purple-pink. Use cobalt blue glass to confirm!
Copper (Cu²⁺)
Blue-green — a bright turquoise. Very distinctive, easy to spot!