1. Attempt
Write the answer and working before opening the solution.
Original Practice Bank
IGCSE Chemistry Topical Questions and Practice
24 original questions across all 12 syllabus topics, worth 58 marks in total. Filter the bank, attempt each question without opening the answer, then record the rule behind every lost mark.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-11.
How to use the bank
2. Mark
Award only the stated mark points, not a vague “close enough”.
3. Classify
Record knowledge, calculation, application, wording or practical error.
4. Retest
Use a fresh question testing the same rule after the correction.
These are independently written practice questions, not reproductions of complete Cambridge examination papers. Paper labels show the closest assessment style; students should use the route and syllabus confirmed by their school or examination centre.
Filter the questions
Showing all 24 questions.
States of Matter Core Paper 1/2 1 mark
Question 1 · Multiple choice · Foundation · AO1
A pure substance changes from a liquid to a gas. Which statement describes the particles after the change?
- A. They become larger and move more slowly.
- B. They remain the same particles and move freely much further apart.
- C. They change into a different substance with weaker atoms.
- D. They remain in fixed positions but vibrate more strongly.
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Answer: B
Why: A change of state is physical. The particles remain chemically unchanged, but in the gas they are much further apart and move rapidly and randomly.
Common error: Saying particles expand or become larger during heating. The spacing changes, not the particle size.
States of Matter Core Paper 3/4 3 marks
Question 2 · Structured · Standard · AO2
Ammonia gas and hydrogen chloride gas diffuse from opposite ends of a long tube. A white ring forms closer to the hydrogen chloride end. Explain why. [3]
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Answer: Ammonia molecules have a lower relative molecular mass than hydrogen chloride molecules [1]. They therefore move/diffuse faster [1], so ammonia travels further along the tube before the gases meet and form the white ring [1].
Why: The observation must be connected to relative molecular mass, diffusion speed and the meeting position.
Common error: Writing only that ammonia is lighter without linking this to faster diffusion and the ring position.
Atoms, Elements and Compounds Core Paper 1/2 1 mark
Question 3 · Multiple choice · Foundation · AO1
An atom has proton number 17 and nucleon number 37. How many neutrons does it contain?
- A. 17
- B. 20
- C. 37
- D. 54
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Answer: B
Why: Number of neutrons = nucleon number − proton number = 37 − 17 = 20.
Common error: Using the nucleon number as the neutron number instead of subtracting the proton number.
Atoms, Elements and Compounds Supplement Paper 4 3 marks
Question 4 · Calculation · Standard · AO2
A sample of element X contains 60% X-24, 30% X-25 and 10% X-26. Calculate the relative atomic mass of X. [3]
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Answer: Ar = [(24 × 60) + (25 × 30) + (26 × 10)] ÷ 100 [2] = 24.5 [1].
Why: This is a weighted mean. The result must lie between 24 and 26 and closer to 24 because X-24 is most abundant.
Common error: Adding the isotope masses and dividing by three without using the abundances.
Stoichiometry Supplement Paper 2 1 mark
Question 5 · Multiple choice · Standard · AO2
What volume is occupied by 0.025 mol of a gas at room temperature and pressure?
- A. 60 cm³
- B. 600 cm³
- C. 960 cm³
- D. 2400 cm³
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Answer: B
Why: Volume = 0.025 × 24,000 cm³ = 600 cm³.
Common error: Using 24 with a volume required in cm³, or failing to convert dm³ to cm³.
Stoichiometry Supplement Paper 4 4 marks
Question 6 · Calculation · Challenge · AO2
Magnesium burns in oxygen: 2Mg + O₂ → 2MgO. Calculate the mass of magnesium oxide formed from 4.8 g of magnesium. [Ar: Mg = 24, O = 16] [4]
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Answer: Moles Mg = 4.8 ÷ 24 = 0.20 mol [1]. The Mg:MgO ratio is 1:1, so moles MgO = 0.20 mol [1]. Mr(MgO) = 40 [1]. Mass = 0.20 × 40 = 8.0 g [1].
Why: Pass through moles, apply the equation ratio and convert to the requested mass.
Common error: Multiplying the original mass directly by an atom ratio without converting to moles.
Electrochemistry Core Paper 1/2 1 mark
Question 7 · Multiple choice · Standard · AO1
Molten lead(II) bromide is electrolysed using inert electrodes. Which products form?
- A. Lead at the anode and bromine at the cathode
- B. Hydrogen at the cathode and oxygen at the anode
- C. Lead at the cathode and bromine at the anode
- D. Lead at both electrodes
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Answer: C
Why: Pb²⁺ ions gain electrons at the cathode to form lead. Br⁻ ions lose electrons at the anode to form bromine.
Common error: Reversing the electrodes or treating a molten electrolyte as though water were present.
Electrochemistry Supplement Paper 4 4 marks
Question 8 · Structured · Challenge · AO2
Concentrated aqueous sodium chloride is electrolysed using inert electrodes. State the product at each electrode and write the two half-equations. [4]
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Answer: Cathode product: hydrogen [1], 2H⁺ + 2e⁻ → H₂ (or the accepted water-based cathode half-equation) [1]. Anode product: chlorine [1], 2Cl⁻ → Cl₂ + 2e⁻ [1].
Why: In concentrated brine, hydrogen is formed at the cathode and chloride ions are discharged at the anode.
Common error: Writing sodium at the cathode because Na⁺ is present, or placing electrons on the wrong side of a half-equation.
Chemical Energetics Core Paper 1/2 1 mark
Question 9 · Multiple choice · Foundation · AO1
Which statement describes an exothermic reaction?
- A. The products have more energy than the reactants and heat is absorbed.
- B. The products have less energy than the reactants and heat is released.
- C. The activation energy is always zero.
- D. Every bond-breaking step releases energy.
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Answer: B
Why: An exothermic reaction transfers energy to the surroundings, and the products are at a lower energy level than the reactants.
Common error: Saying bond breaking releases energy. Bond breaking requires energy; bond making releases energy.
Chemical Energetics Supplement Paper 4 4 marks
Question 10 · Calculation · Challenge · AO2
Use the bond energies H–H = 436 kJ mol⁻¹, Cl–Cl = 243 kJ mol⁻¹ and H–Cl = 431 kJ mol⁻¹ to calculate the energy change for H₂ + Cl₂ → 2HCl. [4]
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Answer: Energy to break bonds = 436 + 243 = 679 kJ mol⁻¹ [1]. Energy released forming bonds = 2 × 431 = 862 kJ mol⁻¹ [1]. ΔH = 679 − 862 [1] = −183 kJ mol⁻¹ [1].
Why: Energy change = energy required to break bonds − energy released when new bonds form. The negative answer shows the reaction is exothermic.
Common error: Reversing the subtraction or forgetting that two H–Cl bonds form.
Chemical Reactions Supplement Paper 2 1 mark
Question 11 · Multiple choice · Standard · AO1
What does a catalyst do?
- A. Increases the energy change of the reaction
- B. Provides an alternative pathway with lower activation energy
- C. Increases the energy of every product particle
- D. Changes the equilibrium yield permanently
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Answer: B
Why: A catalyst increases rate by providing an alternative reaction pathway with a lower activation energy. It does not change the overall energy change or equilibrium position.
Common error: Saying a catalyst gives particles more energy or increases the equilibrium yield.
Chemical Reactions Supplement Paper 4 3 marks
Question 12 · Structured · Challenge · AO2
For N₂(g) + 3H₂(g) ⇌ 2NH₃(g), explain why increasing pressure increases the equilibrium yield of ammonia. [3]
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Answer: The reactant side has four moles of gas while the product side has two [1]. Increasing pressure favours the side with fewer gas molecules/moles [1], so equilibrium shifts to the right and ammonia yield increases [1].
Why: The answer needs the gas-mole comparison, the pressure rule and the direction/yield effect.
Common error: Writing only that particles collide more often. That explains rate, not the equilibrium-position change.
Acids, Bases and Salts Core Paper 1/2 1 mark
Question 13 · Multiple choice · Standard · AO2
Which method prepares pure dry copper(II) sulfate crystals from dilute sulfuric acid?
- A. Add excess copper, filter, evaporate to dryness
- B. Add excess copper(II) oxide, filter, concentrate and cool
- C. Titrate sulfuric acid with copper(II) oxide using an indicator
- D. Mix sulfuric acid with sodium chloride and filter
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Answer: B
Why: Copper(II) oxide is an insoluble base. Add it in excess to neutralise all acid, filter off the excess solid, then concentrate and cool the filtrate to crystallise the salt.
Common error: Evaporating to dryness, which can overheat or decompose some hydrated crystals, or choosing copper metal, which does not react readily with dilute sulfuric acid.
Acids, Bases and Salts Core Paper 3/4 4 marks
Question 14 · Structured · Standard · AO2
Describe how to obtain pure dry sodium chloride crystals from aqueous sodium hydroxide and dilute hydrochloric acid. [4]
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Answer: Titrate measured sodium hydroxide with hydrochloric acid using a suitable indicator to find the exact neutralising volumes [1]. Repeat using those volumes without indicator [1]. Heat the neutral solution to concentrate it, then allow it to cool so crystals form [1]. Filter and dry the crystals [1].
Why: Both reactants are soluble, so an excess solid cannot be filtered off. A titration determines exact neutralisation; the preparation is repeated without indicator to avoid contaminating the crystals.
Common error: Adding one soluble reactant in excess and attempting to remove it by filtration.
The Periodic Table Core Paper 1/2 1 mark
Question 15 · Multiple choice · Foundation · AO1
Which trend occurs down Group I?
- A. Reactivity decreases and melting point increases
- B. Reactivity increases and melting point generally decreases
- C. Reactivity and melting point both increase
- D. Reactivity and melting point both remain constant
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Answer: B
Why: Group I metals become more reactive down the group, while their melting points generally decrease.
Common error: Reversing the Group I reactivity trend with the Group VII trend.
The Periodic Table Core Paper 3/4 3 marks
Question 16 · Structured · Standard · AO2
Chlorine water is added to aqueous potassium bromide. State the observation and explain the reaction. [3]
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Answer: The solution becomes orange/brown because bromine forms [1]. Chlorine is more reactive than bromine [1], so chlorine displaces/oxidises bromide ions to bromine [1].
Why: The answer combines observation, product and the Group VII reactivity relationship.
Common error: Writing that bromine displaces chlorine or giving a conclusion without the colour observation.
Metals Core Paper 1/2 1 mark
Question 17 · Multiple choice · Standard · AO2
A metal is more reactive than carbon. Which extraction method is generally required?
- A. Reduction of its oxide by carbon
- B. Electrolysis of a molten ionic compound
- C. Heating the metal ore in air only
- D. Filtration from an aqueous solution
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Answer: B
Why: Metals above carbon in the reactivity series cannot generally be extracted by carbon reduction and require electrolysis of a molten compound.
Common error: Choosing carbon reduction for a metal more reactive than carbon.
Metals Core Paper 3/4 4 marks
Question 18 · Structured · Standard · AO2
Explain how painting prevents iron from rusting and why a deep scratch can make the protection fail. [4]
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Answer: Paint forms a barrier that prevents water from reaching the iron [1] and prevents oxygen from reaching it [1]. A deep scratch exposes iron [1], allowing both water and oxygen to contact the metal so rusting can occur at the damaged area [1].
Why: Rusting requires both oxygen and water. Barrier protection works only while the coating remains intact.
Common error: Saying paint neutralises rust or naming only oxygen without water.
Chemistry of the Environment Core Paper 1/2 1 mark
Question 19 · Multiple choice · Foundation · AO1
Which pollutant is formed by incomplete combustion and is toxic because it reduces the blood's ability to carry oxygen?
- A. Carbon dioxide
- B. Carbon monoxide
- C. Sulfur dioxide
- D. Nitrogen
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Answer: B
Why: Carbon monoxide is produced during incomplete combustion and is toxic because it binds strongly to haemoglobin.
Common error: Choosing carbon dioxide because it is associated with combustion, without recognising the incomplete-combustion and toxicity clues.
Chemistry of the Environment Core Paper 3/4 4 marks
Question 20 · Structured · Standard · AO2
Explain how an increase in atmospheric carbon dioxide can contribute to climate change. [4]
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Answer: Carbon dioxide absorbs outgoing infrared radiation from Earth [1] and re-emits some of it [1], reducing the rate at which energy escapes to space [1]. This enhances the greenhouse effect and can increase average global temperature, contributing to climate change [1].
Why: The answer should describe the radiation/energy mechanism rather than only state that carbon dioxide is a greenhouse gas.
Common error: Saying carbon dioxide destroys the ozone layer. The greenhouse effect and ozone depletion are different processes.
Organic Chemistry Core Paper 1/2 1 mark
Question 21 · Multiple choice · Foundation · AO1
What is observed when aqueous bromine is shaken with an alkene?
- A. Colourless to orange
- B. Orange to colourless
- C. Blue to colourless
- D. A white precipitate forms
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Answer: B
Why: Bromine adds across the carbon-carbon double bond and aqueous bromine changes from orange to colourless.
Common error: Writing 'clear' instead of colourless, or reversing the colour change.
Organic Chemistry Core + Supplement Paper 4 5 marks
Question 22 · Structured · Challenge · AO2
Compare fermentation of glucose with hydration of ethene as methods of manufacturing ethanol. Give two differences and write the fermentation equation. [5]
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Answer: Fermentation uses a renewable sugar feedstock whereas hydration uses ethene obtained from petroleum [1]. Fermentation is slow and batch-based whereas hydration is fast and continuous [1]. Fermentation uses yeast at about 25-35°C without oxygen, whereas hydration uses steam, phosphoric acid, about 300°C and 60 atm [1 for a valid conditions comparison]. C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ [2 for correct formulae and balancing].
Why: Comparison points must mention both methods. Conditions should not be mixed between the routes.
Common error: Giving two separate descriptions without direct comparisons, or treating complete combustion as a route from ethanol to ethanoic acid.
Experimental Techniques and Chemical Analysis Core Paper 1/2/6 1 mark
Question 23 · Multiple choice · Foundation · AO3
Which apparatus is most suitable for transferring exactly 25.0 cm³ of a solution for a titration?
- A. Beaker
- B. Measuring cylinder
- C. Volumetric pipette
- D. Conical flask
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Answer: C
Why: A volumetric pipette is designed to transfer one fixed volume with greater precision than a measuring cylinder.
Common error: Choosing a measuring cylinder because it has a scale, without considering the required fixed precise volume.
Experimental Techniques and Chemical Analysis Core Paper 6 5 marks
Question 24 · Practical evaluation · Challenge · AO3
A student measures temperature change in a reaction using a glass beaker and records one reading after 60 seconds. Identify two limitations and give a matching improvement for each. [5]
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Answer: Heat is lost to the beaker and surroundings, so the measured temperature change is too small [1]; use an insulated polystyrene cup with a lid [1]. The maximum temperature may be missed because only one reading is taken [1]; record continuously or at short regular intervals with a temperature probe [1]. Explain that the probe/interval readings allow the maximum to be identified [1].
Why: Each improvement must address the named mechanism. Repeating the same poorly insulated method does not remove the heat loss.
Common error: Writing 'human error' or 'use better equipment' without identifying the cause and matched correction.
What this first practice bank covers
The bank includes two original questions per official topic, combining recall, calculation, structured explanation and practical evaluation. It is a foundation for a larger question system, not a claim that 24 questions replace full topical and paper practice.
States of Matter
2 questions · 4 marks
Atoms, Elements and Compounds
2 questions · 4 marks
Stoichiometry
2 questions · 5 marks
Electrochemistry
2 questions · 5 marks
Chemical Energetics
2 questions · 5 marks
Chemical Reactions
2 questions · 4 marks
Acids, Bases and Salts
2 questions · 5 marks
The Periodic Table
2 questions · 4 marks
Metals
2 questions · 5 marks
Chemistry of the Environment
2 questions · 5 marks
Organic Chemistry
2 questions · 6 marks
Experimental Techniques and Chemical Analysis
2 questions · 6 marks
Build the next practice step from the error
| Error found | Next action |
|---|---|
| Missing fact or definition | Retrieve it from memory, then answer a fresh one-mark question. |
| Calculation setup | Write the conversion map and complete three variations with full working. |
| Incomplete explanation | Build the cause-and-effect chain one mark point at a time. |
| Command-word mismatch | Rewrite the answer as describe, explain, deduce or evaluate as required. |
| Practical evaluation | Pair the specific error with its effect and a matching improvement. |
| Rushed MCQ | Explain why each distractor is wrong before doing another timed set. |
Need help interpreting the pattern behind the mistakes?
Send the student's year, Core or Extended route, recent score and the questions that caused difficulty. The compulsory trial is a paid one-hour teaching lesson at the assigned teacher's hourly rate.