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IGCSE Chemistry

IGCSE Chemistry tests for ions, gases and flame colours, all on one page (Paper 4 & Paper 6)

Precipitate colours, flame colours and gas tests are the most memorising students do before the exam, and the marks usually go on wording rather than knowledge. This page has every table in the exact words of Cambridge's Notes for use in qualitative analysis, a dropper where you add NaOH and NH₃ a drop at a time and then in excess, and a mystery solution to identify, Paper 6 style.

The short answer

Every cation test has 3 parts to write: the full reagent name (aqueous sodium hydroxide / aqueous ammonia) · what you see (colour + precipitate) · what happens in excess (soluble or insoluble in excess).

The look-alike pairs are only told apart in excess: Al³⁺ vs Zn²⁺ with excess NH₃ · Cr³⁺ vs Fe²⁺ with excess NaOH · Al³⁺ vs Ca²⁺ with excess NaOH.

Which papers give you the table, and what you must learn

The 0620 syllabus for 2026–2028 says the Notes for use in qualitative analysis are provided for Paper 5 and Paper 6 only. Papers 1–4 give you just the Periodic Table, so a Paper 4 candidate has to know every table on this page.

Edexcel 4CH1 gives no such table in any paper, 1C or 2C: you learn it all.

Tap a row to highlight it

  • 0620 Paper 1 / 2 (multiple choice)

    Are the Notes for use in qualitative analysis given?No, only the Periodic Table

    What it means for youLearn the results by heart

  • 0620 Paper 3 / 4 (Theory)

    Are the Notes for use in qualitative analysis given?No, only the Periodic Table

    What it means for youLearn the tests, colours and wording

  • 0620 Paper 5 / 6 (Practical / ATP)

    Are the Notes for use in qualitative analysis given?Yes, printed at the back of the paper

    What it means for youLook things up, but you still choose the reagents, the order and the full wording

  • Edexcel 4CH1 Paper 1C / 2C

    Are the Notes for use in qualitative analysis given?Not in any paper

    What it means for youLearn it all

Source: 0620 syllabus 2026–2028: "Notes for use in qualitative analysis are provided for both Paper 5 and Paper 6."

Try it: add NaOH and NH₃ yourself

Choose a cation and a reagent, add a few drops, then add in excess and watch which precipitates dissolve. The bold line is the wording you can write in the exam. Once it feels easy, press Mystery solution and work out the ion yourself.

Reagent (a fresh tube each time you switch)

Write in the exam

No reagent added yet

Cu²⁺ · copper(II)

Cation tests

The 8 cations in 0620, worded exactly as in the Notes for use in qualitative analysis.

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  • Al³⁺ (aluminium)

    Aqueous sodium hydroxide, a few drops → excesswhite ppt., soluble in excess, giving a colourless solution

    Aqueous ammonia, a few drops → excesswhite ppt., insoluble in excess

  • NH₄⁺ (ammonium)

    Aqueous sodium hydroxide, a few drops → excessammonia produced on warming: turns damp red litmus paper blue

    Aqueous ammonia, a few drops → excess—

  • Ca²⁺ (calcium)

    Aqueous sodium hydroxide, a few drops → excesswhite ppt., insoluble in excess

    Aqueous ammonia, a few drops → excessno ppt. or very slight white ppt.

  • Cr³⁺ (chromium(III))

    Aqueous sodium hydroxide, a few drops → excessgreen ppt., soluble in excess

    Aqueous ammonia, a few drops → excessgreen ppt., insoluble in excess

  • Cu²⁺ (copper(II))

    Aqueous sodium hydroxide, a few drops → excesslight blue ppt., insoluble in excess

    Aqueous ammonia, a few drops → excesslight blue ppt., soluble in excess, giving a dark blue solution

  • Fe²⁺ (iron(II))

    Aqueous sodium hydroxide, a few drops → excessgreen ppt., insoluble in excess, ppt. turns brown near surface on standing

    Aqueous ammonia, a few drops → excessgreen ppt., insoluble in excess, ppt. turns brown near surface on standing

  • Fe³⁺ (iron(III))

    Aqueous sodium hydroxide, a few drops → excessred-brown ppt., insoluble in excess

    Aqueous ammonia, a few drops → excessred-brown ppt., insoluble in excess

  • Zn²⁺ (zinc)

    Aqueous sodium hydroxide, a few drops → excesswhite ppt., soluble in excess, giving a colourless solution

    Aqueous ammonia, a few drops → excesswhite ppt., soluble in excess, giving a colourless solution

Wording exactly as in the 0620 Notes for use in qualitative analysis. ppt. = precipitate. Pairs told apart in excess: Al³⁺/Zn²⁺ (excess NH₃), Cr³⁺/Fe²⁺ (excess NaOH), Al³⁺/Ca²⁺ (excess NaOH).

Flame tests

The 6 colours to learn. The usual slip: K⁺ is lilac, not purple.

  • Li⁺ lithiumred
  • Na⁺ sodiumyellow
  • K⁺ potassiumlilac
  • Ca²⁺ calciumorange-red
  • Ba²⁺ bariumlight green
  • Cu²⁺ copper(II)blue-green
Use a clean (nichrome or platinum) wire, dip it in the sample and hold it in a colourless flame (air hole open). Write lilac, not purple or pink. On-screen colours are illustrations; the exam uses these words.

Anion tests

What to remember is what goes in first: halides and sulfate are always acidified with dilute nitric acid first; nitrate uses NaOH and aluminium foil, then you test for the ammonia given off.

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  • Carbonate, CO₃²⁻

    Testadd dilute acid, then test for carbon dioxide gas

    Resulteffervescence, carbon dioxide produced (turns limewater milky)

  • Chloride, Cl⁻

    Testacidify with dilute nitric acid, then add aqueous silver nitrate

    Resultwhite ppt.

  • Bromide, Br⁻

    Testacidify with dilute nitric acid, then add aqueous silver nitrate

    Resultcream ppt.

  • Iodide, I⁻

    Testacidify with dilute nitric acid, then add aqueous silver nitrate

    Resultyellow ppt.

  • Sulfate, SO₄²⁻

    Testacidify with dilute nitric acid, then add aqueous barium nitrate

    Resultwhite ppt.

  • Nitrate, NO₃⁻

    Testadd aqueous sodium hydroxide, then aluminium foil; warm carefully

    Resultammonia produced (turns damp red litmus paper blue)

  • Sulfite, SO₃²⁻

    Testadd a small volume of acidified aqueous potassium manganate(VII)

    Resultthe acidified aqueous potassium manganate(VII) changes colour from purple to colourless

Why acidify first: the acid removes carbonate, which would give a false precipitate. Never use HCl before AgNO₃: it adds Cl⁻ itself, so the test is always positive. (Brackets in the result column = the follow-up gas test.)

The 6 gas tests

Each row is the one sentence that scores. Keep the splints straight: lighted for H₂, glowing for O₂.

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  • Ammonia, NH₃

    Test and test resultturns damp red litmus paper blue

  • Carbon dioxide, CO₂

    Test and test resultturns limewater milky

  • Chlorine, Cl₂

    Test and test resultbleaches damp litmus paper

  • Hydrogen, H₂

    Test and test result'pops' with a lighted splint

  • Oxygen, O₂

    Test and test resultrelights a glowing splint

  • Sulfur dioxide, SO₂

    Test and test resultturns acidified aqueous potassium manganate(VII) from purple to colourless

Keep the splints straight: a lighted splint → H₂ 'pops'; a glowing splint → O₂ relights it.

Words that lose marks

Limewater is not the trap: milky, cloudy and white precipitate all score. The marks really go on writing clear instead of colourless when a precipitate dissolves in excess, and on giving a colour such as white or blue without the word precipitate.

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  • A precipitate dissolving in excess

    Loses the markdissolves to give a clear solution

    Scoressoluble in excess, giving a colourless solution

  • Adding NaOH / NH₃

    Loses the markwhite · blue

    Scoreswhite precipitate · light blue precipitate

  • Cu²⁺ with excess NH₃

    Loses the markdark blue precipitate

    Scoreslight blue ppt., soluble in excess, giving a dark blue solution

  • Testing for H₂

    Loses the markrelights a splint

    Scores'pops' with a lighted splint

  • Testing for O₂

    Loses the markpops with a lighted splint

    Scoresrelights a glowing splint

  • Litmus paper

    Loses the markturns red litmus blue

    Scoresturns damp red litmus paper blue

  • Testing for halides

    Loses the markadd silver nitrate (or acidify with HCl first)

    Scoresacidify with dilute nitric acid, then add aqueous silver nitrate

  • Flame colour of K⁺

    Loses the markpurple · pink

    Scoreslilac

Limewater is not the trap: milky, cloudy and white precipitate all score. The marks really go on clear (which can still be coloured) instead of colourless, and on a colour with no 'precipitate'. The losing answers are our summary of common slips, not a published mark scheme.

What changes for Edexcel 4CH1

4CH1 asks for less than 0620: cations with NaOH only, no Ba²⁺ flame, no SO₂ test. But it uses barium chloride for sulfate and adds the water tests. For the wider picture, see 0620 vs 4CH1.

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  • Cations

    Cambridge 06208 ions, with NaOH and NH₃

    Edexcel 4CH1NH₄⁺ (test the gas given off) and Cu²⁺, Fe²⁺, Fe³⁺, with NaOH only

  • Flame tests

    Cambridge 06206 ions, including Ba²⁺

    Edexcel 4CH15 ions: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺ (no Ba²⁺)

  • Halides

    Cambridge 0620dilute nitric acid, then aqueous silver nitrate

    Edexcel 4CH1acidified silver nitrate solution

  • Sulfate

    Cambridge 0620dilute nitric acid, then aqueous barium nitrate

    Edexcel 4CH1acidified barium chloride solution (usually acidified with dilute HCl)

  • Carbonate

    Cambridge 0620dilute acid → CO₂ → limewater

    Edexcel 4CH1hydrochloric acid → test the gas given off (CO₂)

  • Other anions

    Cambridge 0620nitrate and sulfite

    Edexcel 4CH1none

  • Gases

    Cambridge 06206, including SO₂

    Edexcel 4CH15: H₂, O₂, CO₂, NH₃, Cl₂ (no SO₂)

  • Water

    Cambridge 0620—

    Edexcel 4CH1anhydrous copper(II) sulfate turns from white to blue · a physical test that water is pure (boils at 100 °C)

The 4CH1 column is from the specification, Issue 3 (Sep 2024), points 2.44–2.50. Everything 4CH1 asks for is inside the 0620 tables above, except the sulfate reagent and the water tests.

Where Boom-Tutor helps

Topic 12 of the course (Experimental techniques and chemical analysis) has a cation station, a spotting tile of 8 wells with NaOH and NH₃ plus 6 flame-test wires, and an anion and gas station. The student adds the reagents, watches the results, and records them in the table's own words: the same skill as Paper 6.

The self-learn IGCSE Chemistry course is ฿4,900, paid once, with access until the exam session. The platform is expected to open around December 2026.

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