Edexcel International GCSE (IGCSE) Chemistry (4CH1) Past Papers 2026

Chemistry 1 — Core and Extended Content

Duration: 2h

Chemistry 2 — Core and Extended Content

Duration: 1h 15m

Intermolecular forces vs covalent bonds — knowing which breaks on melting

Paper 1C 2023 explicitly flagged this as a named area for improvement in the Paper Summary. Examiners noted the phrase 'forces between the bonds' as increasingly common despite scoring 0, and that candidates often omit the word 'weak' when describing intermolecular forces — using 'less' instead of 'a small amount of' energy.

Paper 1C

Collision theory — using 'kinetic energy' and 'frequency of successful collisions' precisely

Paper 1C 2023 Q10(b)(i) was one of the most demanding questions on the paper. The word 'kinetic' was missing from many answers, and candidates did not distinguish between frequency of collisions and frequency of successful collisions (those exceeding activation energy). Use of 'probability' or 'chance' in place of 'frequency' is not accepted.

Paper 1C

Equilibrium — explaining yield changes using endothermic/exothermic direction

Paper 2C 2023 Q7(c) showed most candidates knew the direction of yield change but could not explain it. Many earned only 1 mark out of 2 because they did not link the temperature change to whether the reaction is endothermic or exothermic. The catalyst question also revealed widespread confusion: many candidates believed a catalyst increases yield.

Paper 2C

Electrolysis — ions in fixed positions (solid) vs free to move (molten), and specifying correct species at electrodes

Paper 2C 2024 Q6(c)(i) showed only stronger candidates scoring all 3 marks. First mark (ions in fixed positions/lattice) was the most commonly missed. Third mark (ions free to move → conduct electricity/carry current) was lost because candidates described ion movement but forgot to connect it to electrical conduction. At the anode, 'bromine loses electrons' (rather than 'bromide ions') was not accepted.

Paper 2C

Titration indicators — exact colours for methyl orange in acid and alkali

Paper 2C 2023 Q4(b) showed fewer than half of candidates correctly identifying yellow as the alkaline colour of methyl orange. Orange was common as an incorrect answer (orange is the end-point colour, not the alkali colour). Confusion with phenolphthalein (pink/colourless) was also seen.

Paper 2C

Halogen displacement reactions — terminology, colours of iodine, and writing balanced equations

Paper 1C 2023 Q7(d) was described as 'challenging'. Candidates confused iodine colours (aqueous iodine is red-brown, not purple/grey — those are solid and organic solvent forms). Many gave conditional answers ('if they react then... but if they don't...') rather than describing the specific reactions observed. Balanced ionic/half equations for displacement were poorly attempted.

Paper 1C

Catalytic cracking — correct catalyst, temperature range, and naming both useful products

Paper 2C 2023 Q6(a)(i) showed fewer than half of candidates giving the correct catalyst (H₂SO₄). Silica and alumina were commonly seen instead (confused with steam cracking), and potassium dichromate was also given (it is an oxidising agent, not a catalyst). Paper 2C 2024 Q3(c) showed candidates mentioning supply-and-demand without specifying petrol/alkanes and polymers/alkenes as the products.

Paper 2C

Practical chemistry in unfamiliar contexts — applying knowledge to new experimental setups

Paper 1C 2023 Q6 (precipitate formation in an unfamiliar context) was harder than Q8 (calorimetry, a familiar core practical). Q8(a)(ii) showed many candidates unable to explain why the spirit burner mass must be taken immediately after extinguishing — most said 'to calculate mass burned' rather than explaining that alcohols are volatile and mass loss from evaporation would give an incorrect result.

Paper 1C