Least demanding: Q14, Q23, Q27, Q36, Q37, Q39.
Most demanding: Q4, Q15, Q25, Q34 (correct answer must be fully correct; in Q4 the word “halogen” made C wrong).
One of the most challenging. Options B and C were more popular than the correct answer; “halogen” made option C incorrect.
Fewer than half answered correctly. Option C most common wrong. Reactions involve movement of electrons, not protons.
Stronger candidates did well; many others chose B—misunderstanding bonding in chlorine or the meaning of “pair”.
About one-third correct. Option B describes graphite’s structure but not why it is used as an electrode.
Over a third chose B. Recall the full name: the hydrogen–oxygen fuel cell.
Listed among the least demanding questions overall.
Poorly answered; >? chose C. Confusion over terms: hydrated = with water; anhydrous = with no water.
Small majority correct; some guessing. Recognise an alkaline gas is produced ? think ammonia from an ammonium salt.
Many candidates appeared to be guessing.
Listed among the least demanding questions overall.
Not well answered. Many couldn’t recall reactions of metals with water or dilute acid. C chosen by >?; B chosen often too.
Order of reactivity not determined by many; response distribution suggests guessing. Metals react more vigorously with steam/dilute acid than cold water.
Listed among the least demanding questions overall.
Most common response was B (incorrect). Yeast is a catalyst, not a reactant; catalysts are not used up and shouldn’t appear as reactants.
Listed among the least demanding questions overall.
Listed among the least demanding questions overall.
Challenging: many chose D by counting ‘red’ spots without checking if they represented the same or different dyes.
Weaker candidates chose A/D which would form a pure salt only if salt and water were the only substances. Here the outcome is a mixture of salt and sand.
DIfficult Questions from 2023 IGCSE Biology Past Papers have been listed below along with specific and extremely detailed comments by examiners. Read them carefully, so as to avoid repeating the same mistakes in your own exams. Also this is the ideal exam preparation, as the comments come from the examiners themselves.
Least demanding: Q3, Q8, Q13, Q22, Q26, Q34, Q37, Q40.
Most demanding: Q1 and Q9.
Be cautious with questions like Q7: option B describes a substance correctly but does not answer the question asked.
Most challenging. Cooling curves new to syllabus. Temperature does not change while a substance changes state. C and D most common wrong answers.
Most answered correctly, but some chose B. Correct description of graphite structure but does not explain use as an electrode.
Calculations were challenging. Most common wrong = B, assuming all sodium hydrogencarbonate decomposed.
Some chose C (not correct) but showed understanding of endothermic/exothermic and ?H. A and D rarely chosen.
Half answered correctly; many guessed. A third chose A or B, suggesting they didn’t recognise activation energy remains unchanged.
Nearly all answered correctly. C common wrong: identifies the reduced metal, not the reducing agent.
Tested recall of ammonia from ammonium salts. Recognise alkaline gas. B most common incorrect answer.
Recall of metal reactivity. ~25% did not recall Ca with water or Mg with steam. Some assumed silver reacts with dilute acid ? chose C.
Options B and D not common, but many chose A (wrong). Still recognised correct linkages in polymer.
Addition polymers and repeat units: less than half correct. Some appeared to guess. No strong preference among incorrect options.
Chromatography generally well answered. One-third wrongly chose D, counting ‘red’ spots without checking if same/different dyes.
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