Almost every 0620 Paper 5 has a Question 2 on testing unknown substances, and Paper 6 asks the same tests on paper. By hand, heat solid X in a tube held in the Bunsen flame and hold a glowing splint, limewater or damp litmus at its mouth; dip the nichrome wire in X and hold it in the flame; add acid. Then test solution Y with droppers, a few drops first and then in excess. The bench shows what happens; you choose the exam wording, name the ions and predict one more result. The substances change every attempt. Allow about 30 minutes.
Past-paper referenceOriginal experiment, wording and numbers, written in the style of Cambridge IGCSE Chemistry 0620 Paper 5 (Practical Test) and Paper 6 (Alternative to Practical). It is not copied from a past paper.This type of experiment has come up 67 times (29 in Paper 5, the Practical Test, and 38 in Paper 6, the Alternative to Practical) in the past papers we checked. Show the list
Checked: Cambridge IGCSE Chemistry 0620 Papers 5 and 6, 2020 to 2025. Only the papers in our collection are listed, so the real number may be higher. Question papers are available from Cambridge.
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How this question is marked
Observations (a)
One mark for each box of Table 2.1 (10 marks). Your answer is compared with what actually happened in your own tubes, so a test you never finished (not heated for long enough, no gas test at the mouth, no excess added) cannot score.
Conclusion (b)
What test 1 tells you about solid X: condensation at the cool top of the tube means the solid is hydrated.
Identifying (c)
The gas given off on heating, the metal ion shown by the flame colour, and the cation and anion in solution Y (4 marks).
Prediction (d)
The expected observations, dropwise and in excess, for a named solution you have not tested, using the notes.
Habits that save marks
A few drops first, then excess: pour in excess at once and you never see the precipitate that dissolves.
A gas needs its test and result: “relights a glowing splint” or “turns limewater milky”, not just “oxygen”.
Clean the flame-test wire in acid between samples, or the colours mix and the answer is lost.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.