Experimental techniques and chemical analysis — IGCSE Science - Combined (0653) questions by topic
Chromatography, separation methods and rate-of-reaction graphs run through this topic: reading spot positions on a chromatogram, matching separation processes such as crystallisation to the right description, and testing gases with the correct type of splint. Explain, describe and suggest lead the command words, and each rewards a specific test or step rather than a restated observation.
These 16 real questions, taken from 2023 to 2025 papers, are worth 1 to 13 marks, ranging from a single gas test to a full graph-plotting sequence. Submitting worked answers for instant marking flags quickly whether a described observation, such as unreacted magnesium remaining after fizzing stops, is actually stated rather than just implied.
What examiners look for
- A common slip is describing a glowing splint where the test for hydrogen requires a lighted splint.
- Repeating the stem of the question, such as writing 'this keeps the magnesium submerged', is not credited as a fresh observation.
- Unqualified statements such as 'human error' are marked down where a specific source of imprecision is required.
- Graphs frequently lose marks for unlabelled axes, missing units, or inverted axes.
- Strong answers relate increasing surface area to bringing more of the metal into contact with the acid, and describe unreacted solid magnesium remaining once fizzing has stopped.
May–June 2025, Paper 11
Chromatography separates ink into different colours. Which diagram shows how the apparatus is set up? A beaker with paper hanging fully inside, ink spot on the paper above the…
Answer this question and get it marked →May–June 2025, Paper 12
Sugar dissolves in water to form sugar solution. Which word describes the sugar? A filtrate B residue C solute D solvent
Answer this question and get it marked →Which methods of separation depend on the substances in a mixture having different boiling points? A crystallisation and simple distillation B evaporation and filtration C…
Answer this question and get it marked →May–June 2025, Paper 13
Separate samples of the gases ammonia, chlorine, hydrogen and oxygen are tested with damp blue litmus paper. How many of these gases change the colour of the litmus paper? A 0 B 1…
Answer this question and get it marked →May–June 2025, Paper 21
A chromatogram of dyes X, Y and Z is shown. The baseline is at 0 cm and the solvent front is at 8 cm. Dye X has one spot at 4 cm. Dye Y has spots at about 2.5 cm and 7 cm. Dye Z…
Answer this question and get it marked →May–June 2025, Paper 22
The chromatogram of four different substances is shown. Which substance has an Rf value of 0.6? The chromatogram has a baseline at 0 cm and a solvent front at 20 cm. Four spots A,…
Answer this question and get it marked →Potassium iodide reacts with lead(II) nitrate to produce yellow lead(II) iodide and potassium nitrate. 2KI(aq) + Pb(NO3)2(aq) → PbI2(s) + 2KNO3(aq) Which row describes this…
Answer this question and get it marked →May–June 2025, Paper 23
The diagram shows a chromatogram for a brown ink. The chromatography paper has a baseline at 0 cm where the brown ink spot was placed, and the solvent front is at 14 cm. Three…
Answer this question and get it marked →May–June 2025, Paper 31
Potassium and magnesium are metals. A solid compound contains potassium ions. Describe the use of a flame test to identify potassium ions.
Answer this question and get it marked →May–June 2025, Paper 63
A student investigates a white solid H. The student adds a sample of H to aqueous sodium hydroxide in a boiling tube. The student carefully warms the boiling tube. The student…
Answer this question and get it marked →May–June 2024, Paper 41
Different methods of separation are used for different types of mixtures. Pure water is separated from a solution of salt and water by distillation. Fig. 2.1 shows the apparatus…
Answer this question and get it marked →May–June 2024, Paper 42
Different types of mixtures need different separation processes to isolate the pure substances from the mixture. For each separation process, draw one straight line to the correct…
Answer this question and get it marked →May–June 2024, Paper 52
You are going to investigate the identity of unknown solution X. Pour solution X into test-tubes 1 to 4 and soak a wooden splint in test-tube 4. Do each test in Table 2.1 and…
Answer this question and get it marked →May–June 2024, Paper 62
A student investigates the identity of unknown solution X. The student does each test described in Table 2.1 on separate samples of solution X. The observations are shown in Table…
Answer this question and get it marked →May–June 2024, Paper 63
A student investigates a green liquid. The green liquid is a mixture of substances dissolved in water. Some of these substances are coloured and the others are colourless.…
Answer this question and get it marked →October–November 2023, Paper 61
When magnesium ribbon is added to dilute hydrochloric acid, the mixture fizzes and makes hydrogen gas. State the test used to confirm the presence of hydrogen gas and give the…
Answer this question and get it marked →Other IGCSE Science - Combined topics
- Practical skills (96)
- Motion, forces and energy (53)
- Electricity and magnetism (38)
- Waves (32)
- Human nutrition (23)
- Acids, bases and salts (22)
- Organisms and their environment (21)
- Organic chemistry (21)
- Reproduction (20)
- Thermal physics (20)
- Plant nutrition (19)
- The Periodic Table (18)