References only, not question text. Open Official paper ↗ where Cambridge publishes the paper,
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school. “Paper 42” means Paper 4, variant 2.
Practice questions
Original questions written by HomiLabs in the style of the exam, with answers and mark schemes. They are not
Cambridge past paper questions and have not been reviewed by Cambridge. Try each one before opening the answer.
Q1Extraction of metals · Core · Paper 1 style · 1 mark
(a)Which metal is extracted from its oxide by electrolysis rather than by heating with carbon?[1]
Show answer
(a) A aluminium
Aluminium is above carbon in the reactivity series, so carbon cannot reduce aluminium oxide. Iron (B) is below carbon and is extracted with carbon (as carbon monoxide) in the blast furnace.
Q2Extraction of metals · Core · Paper 2 style · 4 marks
Iron is made in a blast furnace from hematite, coke, limestone and hot air.
(a)State the purpose of each raw material:(i) coke(ii) limestone(iii) hot air[3]
(b)Name the main ore of iron used.[1]
Show answer
(a) (i) burns to provide heat and forms carbon monoxide, the reducing agent (ii) removes acidic impurities such as silicon(IV) oxide, forming slag (iii) provides oxygen for the coke to burn
B1 each.
(b) hematite (iron(III) oxide, Fe₂O₃)
B1.
Q3Extraction of metals · Core · Paper 2 style · 5 marks
(a)Write equations for: (i) the formation of carbon monoxide from coke in two steps (ii) the reduction of iron(III) oxide by carbon monoxide.[3]
(b)In the reaction in (a)(ii), name the substance that is reduced and the reducing agent.[2]
Show answer
(a) (i) C + O₂ → CO₂ then CO₂ + C → 2CO (ii) Fe₂O₃ + 3CO → 2Fe + 3CO₂
B1 C + O₂ → CO₂; B1 CO₂ + C → 2CO; B1 balanced reduction equation.
(b) iron(III) oxide is reduced; carbon monoxide is the reducing agent
B1 each.
Q4Extraction of metals · Standard · Paper 2 style · 5 marks
(a)Limestone decomposes in the furnace. Write the equation.[1]
(b)Calcium oxide reacts with silicon(IV) oxide (sand) to form slag. Write the equation and name the slag.[2]
(c)Explain this reaction in terms of the types of oxide involved.[1]
(d)Explain how the slag and the molten iron are removed separately.[1]
Show answer
(a) CaCO₃ → CaO + CO₂
B1.
(b) CaO + SiO₂ → CaSiO₃; calcium silicate
B1 equation; B1 name.
(c) Calcium oxide is a basic oxide and silicon(IV) oxide is an acidic oxide, so they react (neutralise) to form a salt.
B1.
(d) Slag is less dense, so it floats on the molten iron and is tapped off at a higher level.
B1.
Q5Extraction of metals · Standard · Paper 2 style · 6 marks
Aluminium is extracted by electrolysis of aluminium oxide (from bauxite) dissolved in molten cryolite, using carbon electrodes.
(a)Explain why aluminium oxide is dissolved in molten cryolite rather than melted on its own.[2]
(b)Write the equations for the reactions at the cathode and at the anode.[2]
(c)Explain why the carbon anodes must be replaced regularly.[2]
Show answer
(a) Aluminium oxide has a very high melting point (over 2000 °C); the solution in molten cryolite works at a much lower temperature (about 950 °C), saving energy and cost.
B1 lowers the operating temperature; B1 saves energy / cost.
(c) The oxygen produced at the hot anodes reacts with the carbon to form carbon dioxide, so the anodes burn away.
B1 oxygen reacts with carbon; B1 forms CO₂ / anodes wear away.
Q6Extraction of metals · Standard · Paper 4 style · 5 marks
(a)Predict which of these oxides can be reduced by heating with carbon: magnesium oxide, zinc oxide, copper(II) oxide, aluminium oxide. Explain your choice.[3]
(b)A student heats black copper(II) oxide with carbon powder in a crucible. Write the balanced equation and state what is seen at the end.[2]
Show answer
(a) zinc oxide and copper(II) oxide; zinc and copper are less reactive than carbon, so carbon can remove the oxygen. Magnesium and aluminium are more reactive than carbon.
B1 zinc oxide; B1 copper(II) oxide (and no others); B1 reason based on position relative to carbon.
Q7Extraction of metals · Challenge · Paper 2 style · 5 marks
(a)Calculate the maximum mass of iron that can be obtained from 800 tonnes of iron(III) oxide. (Ar: Fe = 56, O = 16)[2]
(b)A sample of hematite ore is 90 % iron(III) oxide by mass. Calculate the maximum mass of iron from 1000 tonnes of this ore.[2]
(c)Suggest why the actual mass of iron produced is less than this.[1]
Show answer
(a) 560 tonnes
M1 Mr Fe₂O₃ = 160 and 112 t Fe in every 160 t; A1 800 × 112 ÷ 160 = 560 t.
(b) 630 tonnes
M1 900 t Fe₂O₃; A1 900 × 112 ÷ 160 = 630 t.
(c) Not all the iron oxide is reduced / some iron is lost in the slag.
B1.
Q8Extraction of metals · Challenge · Paper 2 style · 5 marks
(a)The overall reaction is 2Al₂O₃ → 4Al + 3O₂. Calculate the mass of aluminium produced from 51 tonnes of aluminium oxide. (Ar: Al = 27, O = 16)[2]
(b)Calculate the mass of oxygen produced at the same time.[1]
(c)Give two reasons why recycling aluminium cans is better than extracting new aluminium.[2]
Show answer
(a) 27 tonnes
M1 Mr Al₂O₃ = 102, 54 t Al per 102 t; A1 51 × 54 ÷ 102 = 27 t.
(b) 24 tonnes
B1 51 − 27 = 24 t (conservation of mass).
(c) Recycling uses much less electrical energy; it conserves bauxite ore; it reduces waste in landfill; less mining and land damage.
1 mark each for any two.
Q9Properties & uses of metals · Core · Paper 1 style · 1 mark
(a)Copper is used for electrical wiring in houses. Which two properties make it suitable?[1]
Show answer
(a) A good electrical conductor and ductile
Wiring needs a metal that conducts electricity well and can be drawn into wires (ductile). B is wrong: copper is not brittle, and density is not the reason.
Q10Properties & uses of metals · Core · Paper 2 style · 4 marks
(a)Give three physical properties that are typical of metals.[3]
(b)State one chemical property that is typical of metals.[1]
Show answer
(a) Any three of: good conductors of electricity; good conductors of heat; malleable; ductile; shiny when freshly cut; high melting and boiling points; high density; sonorous.
1 mark each for any three.
(b) Metals form basic oxides / form positive ions / reactive metals produce hydrogen with dilute acids.
B1 any one.
Q11Properties & uses of metals · Standard · Paper 2 style · 5 marks
(a)Explain why aluminium is used for overhead power cables. Give two properties.[2]
(b)Explain why aluminium is used to make aircraft bodies.[2]
(c)Explain why copper is used for water pipes.[1]
Show answer
(a) Good electrical conductor; low density (light, so pylons can support it); resistant to corrosion.
1 mark each for any two.
(b) Low density (strong but light, especially as an alloy) and resistant to corrosion because of its oxide layer.
B1 low density; B1 corrosion resistance.
(c) It does not react with water / is unreactive and does not corrode easily; it is easy to bend (malleable).
B1.
Q12Properties & uses of metals · Standard · Paper 2 style · 6 marks
(a)Write a balanced equation for the reaction of magnesium with dilute hydrochloric acid, and give one observation.[2]
(b)Calcium reacts with cold water. Write the balanced equation and describe a test for the gas produced.[3]
(c)State what is seen when copper is added to dilute hydrochloric acid, and explain.[1]
(b) Ca + 2H₂O → Ca(OH)₂ + H₂; a lighted splint gives a squeaky pop.
B1 formulae; B1 balanced; B1 test and result.
(c) No reaction (no bubbles), because copper is below hydrogen in the reactivity series.
B1.
Q13Properties & uses of metals · Challenge · Paper 2 style · 6 marks
Data for four metals:metal: density / g/cm³, relative electrical conductivity, cost, resistance to corrosionW: 2.7, 61, low, goodX: 8.9, 100, high, goodY: 7.9, 17, low, poorZ: 19.3, 73, very high, excellent
(a)Which metal is best for overhead power cables? Use the data to explain.[2]
(b)Calculate the relative conductivity divided by density for W and for X. Give your answers to 3 significant figures and explain what they show.[3]
(c)Suggest why Y is not used for a bridge near the sea in Gwadar unless it is protected.[1]
Show answer
(a) W: low density with good conductivity, low cost and good corrosion resistance.
B1 W; B1 two supporting data points.
(b) W: 22.6; X: 11.2. W conducts about twice as well as X for the same mass of cable.
M1 61 ÷ 2.7; A1 22.6 and 11.2; B1 W better per unit mass.
(c) Y has poor corrosion resistance; it would corrode (rust) quickly in moist, salty air.
B1.
Q14Properties & uses of metals · Challenge · Paper 2 style · 4 marks
(a)Aluminium is high in the reactivity series but aluminium cooking pots do not react with water. Explain why.[2]
(b)A piece of aluminium foil is placed in dilute hydrochloric acid. At first nothing happens; after a few minutes bubbles appear quickly. Suggest an explanation.[2]
Show answer
(a) Aluminium is covered by a thin, unreactive layer of aluminium oxide that sticks to the surface and stops water reaching the metal.
B1 oxide layer; B1 layer protects / prevents further reaction.
(b) The acid first reacts with / removes the oxide layer (no gas). Once the metal is exposed, the reactive aluminium reacts with the acid, giving hydrogen.
B1 oxide layer removed by acid first; B1 then Al reacts producing hydrogen.
Q15Reactivity series & displacement · Core · Paper 1 style · 1 mark
(a)Which mixture reacts?[1]
Show answer
(a) B iron and aqueous copper(II) sulfate
Iron is more reactive than copper, so it displaces copper from solution. In A, copper is less reactive than zinc, so there is no reaction.
Q16Reactivity series & displacement · Core · Paper 2 style · 5 marks
(a)A piece of magnesium ribbon is placed in blue aqueous copper(II) sulfate. Give two observations.[2]
(b)Write the balanced equation and the ionic equation for the reaction.[2]
(c)Explain why this is called a displacement reaction.[1]
Show answer
(a) The blue colour fades; a pink-brown solid (copper) forms on the magnesium; the solution gets warm; the magnesium gets smaller.
(c) The more reactive magnesium takes the place of (displaces) the less reactive copper from its compound.
B1.
Q17Reactivity series & displacement · Standard · Paper 4 style · 5 marks
A student places small pieces of metals P, Q and R in solutions of their nitrates and records whether a reaction happens (✓) or not (✗).P in Q nitrate: ✓ P in R nitrate: ✓Q in P nitrate: ✗ Q in R nitrate: ✓R in P nitrate: ✗ R in Q nitrate: ✗
(a)Put the metals P, Q and R in order of reactivity, most reactive first. Explain how you decided.[2]
(b)Predict whether R would react with dilute hydrochloric acid if R is copper. Explain.[1]
(c)Give one safety precaution and one way to make the comparison fair.[2]
Show answer
(a) P > Q > R. P displaces both Q and R; Q displaces only R; R displaces neither.
B1 order; B1 explanation.
(b) No; copper is below hydrogen in the reactivity series.
B1.
(c) Wear eye protection; use the same size / mass of each metal and the same volume and concentration of solution.
B1 each.
Q18Reactivity series & displacement · Standard · Paper 2 style · 5 marks
(a)Describe how potassium, calcium and copper react (if at all) with cold water.[3]
(b)Magnesium reacts only very slowly with cold water but reacts with steam. Write the equation for the reaction with steam.[1]
(c)Explain the order of reactivity in terms of the tendency to form positive ions.[1]
Show answer
(a) Potassium: reacts violently, melts, moves around and the hydrogen burns with a lilac flame. Calcium: reacts steadily with bubbling, forming a cloudy solution. Copper: no reaction.
B1 each.
(b) Mg + H₂O → MgO + H₂
B1.
(c) The more reactive the metal, the more easily its atoms lose electrons to form positive ions.
B1.
Q19Reactivity series & displacement · Challenge · Paper 2 style · 5 marks
(a)The thermite reaction is used to weld railway lines: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe. Explain why this reaction happens.[1]
(b)Identify the oxidising agent and the reducing agent.[2]
(c)Calculate the mass of iron formed from 5.4 g of aluminium. (Ar: Al = 27, Fe = 56)[2]
Show answer
(a) Aluminium is more reactive than iron, so it removes oxygen from iron(III) oxide.
M1 moles Al = 5.4 ÷ 27 = 0.20 = moles Fe; A1 0.20 × 56 = 11.2 g.
Q20Reactivity series & displacement · Challenge · Paper 4 style · 6 marks
A metal M is tested.M in aqueous zinc sulfate: no changeM in aqueous copper(II) sulfate: brown coating forms, solution fadesM in dilute sulfuric acid: slow bubbling
(a)Use the results to place M in the reactivity series relative to zinc, copper and hydrogen.[2]
(b)M forms M²⁺ ions. Write an ionic equation for the reaction of M with copper(II) ions.[1]
(c)Plan an experiment using temperature changes to check whether M is more reactive than iron. Give the measurements and how you would decide.[3]
Show answer
(a) Below zinc, above copper and above hydrogen.
B1 between zinc and copper; B1 above hydrogen (reacts with acid).
(b) M + Cu²⁺ → M²⁺ + Cu
B1.
(c) Add equal masses of powdered M and powdered iron separately to equal volumes of the same copper(II) sulfate solution in an insulated cup; measure the starting and highest temperatures; the metal giving the larger temperature rise is more reactive.
B1 same mass/particle size and volume/concentration of CuSO₄; B1 measure initial and maximum temperature; B1 larger rise = more reactive.
Q21Corrosion & rust prevention · Core · Paper 4 style · 5 marks
A student sets up four test tubes, each containing an iron nail, and leaves them for one week.A: nail in tap water, open to the airB: nail in boiled water with a layer of oil on topC: nail in dry air with anhydrous calcium chloride, tube stopperedD: nail in salt water, open to the air
(a)In which tubes does the nail rust?[1]
(b)Explain the purpose of boiling the water and adding a layer of oil in tube B.[2]
(c)What do the results show is needed for iron to rust?[1]
(d)Suggest which tube rusts fastest and why.[1]
Show answer
(a) A and D
B1 both, no others.
(b) Boiling removes dissolved air (oxygen); the oil stops air dissolving back into the water.
B1 each.
(c) Both water and oxygen (air).
B1.
(d) D: salt water speeds up rusting.
B1.
Q22Corrosion & rust prevention · Core · Paper 1 style · 1 mark
(a)Which method protects a steel ship's hull by sacrificial protection?[1]
Show answer
(a) C attaching blocks of zinc to the hull
Zinc is more reactive than iron, so it corrodes instead of the steel. A, B and D are barrier methods and stop protecting if the coating is damaged.
Q23Corrosion & rust prevention · Standard · Paper 2 style · 5 marks
Galvanised steel sheets are widely used for roofs of sheds and cattle shelters in rural Punjab.
(a)State what is meant by galvanising.[1]
(b)A galvanised steel roof sheet is scratched, exposing the steel. Explain why the steel still does not rust.[3]
(c)Explain why a painted steel gate starts to rust when the paint is chipped.[1]
Show answer
(a) Coating iron or steel with a layer of zinc.
B1.
(b) Zinc is more reactive than iron, so zinc loses electrons (is oxidised) in preference to iron. The zinc corrodes instead of the iron (sacrificial protection).
B1 zinc more reactive; B1 zinc oxidised / loses electrons instead of iron; B1 iron protected even where exposed.
(c) Paint is only a barrier; once broken, water and oxygen reach the iron.
B1.
Q24Corrosion & rust prevention · Standard · Paper 2 style · 6 marks
(a)Give the chemical name of rust and write a word equation for its formation.[2]
(b)Suggest why cars in Karachi rust faster than cars in a dry inland city.[2]
(c)Give two barrier methods for preventing rusting of a bicycle and say which part each is used for.[2]
Show answer
(a) hydrated iron(III) oxide; iron + water + oxygen → hydrated iron(III) oxide
B1 each.
(b) Karachi is coastal: the air is humid and contains salt, and salt (an electrolyte) speeds up rusting.
B1 more moisture; B1 salt speeds up rusting.
(c) Paint for the frame; oil or grease for the chain; plastic coating for the basket / handlebars.
1 mark each for any two matched methods.
Q25Corrosion & rust prevention · Challenge · Paper 4 style · 7 marks
A student pushes damp iron wool into the bottom of a measuring cylinder and turns it upside down in a trough of water. The volume of air trapped is 100.0 cm³ at the start. After eight days, when the reading has stopped changing, the volume is 79.2 cm³.
(a)Calculate the percentage of the air used up.[2]
(b)Name the gas that was used up and explain why the water level rose.[2]
(c)Suggest why the student waited until the reading stopped changing.[1]
(d)Suggest one source of error and one improvement.[2]
(b) Oxygen; it reacted with the iron to form rust, so the volume of gas fell and water moved up to take its place.
B1 oxygen; B1 explanation.
(c) To make sure all the oxygen had reacted.
B1.
(d) Error: temperature or pressure changes alter the gas volume; reading not at eye level / meniscus. Improvement: keep at constant temperature and read at the same temperature; use more iron wool (or wet it) so all the oxygen reacts; repeat and average.
B1 error; B1 matching improvement.
Q26Alloys · Core · Paper 2 style · 4 marks
Sialkot is known for making surgical instruments and cutlery from stainless steel.
(a)State what is meant by an alloy.[1]
(b)Name the two metals in brass.[1]
(c)Stainless steel contains iron, chromium and nickel. Give one use of stainless steel and the property that makes it suitable.[2]
Show answer
(a) A mixture of a metal with one or more other elements (usually metals).
B1.
(b) copper and zinc
B1 both.
(c) Cutlery / kitchen sinks / surgical instruments; it is hard and resists rusting.
B1 use; B1 property.
Q27Alloys · Core · Paper 1 style · 1 mark
(a)Why is an alloy usually harder than the pure metal it is made from?[1]
Show answer
(a) A Atoms of different sizes disrupt the regular layers, so the layers cannot slide easily.
Different-sized atoms distort the layers, making it harder for layers to slide. B and C are wrong: alloys still have metallic bonding with delocalised electrons.
Q28Alloys · Standard · Paper 2 style · 4 marks
(a)Explain, in terms of structure, why brass is harder than pure copper. You may describe a diagram in words.[3]
(b)Brass is used for door handles and musical instruments. Give one reason, other than hardness, why brass is used rather than iron.[1]
Show answer
(a) In pure copper the atoms are all the same size and arranged in regular layers that slide easily. In brass the zinc atoms are a different size; they distort the layers so the layers cannot slide over each other easily, so brass is harder.
B1 pure metal: regular layers slide easily; B1 alloy: atoms of different sizes disrupt layers; B1 layers cannot slide easily → harder.
(b) It does not rust / resists corrosion; attractive gold colour.
B1.
Q29Alloys · Standard · Paper 2 style · 4 marks
A metallurgist measures the hardness of copper–zinc alloys (higher number = harder).% zinc: 0, 10, 20, 30, 40hardness: 40, 52, 63, 75, 86
(a)Describe how the hardness changes as the percentage of zinc increases.[1]
(b)Estimate the hardness of an alloy containing 25 % zinc.[1]
(c)Suggest why an alloy with 30 % zinc is better than pure copper for making screws and hinges.[2]
Show answer
(a) Hardness increases as the percentage of zinc increases (by about 11–12 units per 10 % zinc).
B1.
(b) 69 (accept 68–70)
B1 midway between 63 and 75.
(c) It is much harder (75 vs 40) so it is stronger and less easily bent or worn, while still resisting corrosion.
B1 harder / stronger; B1 data quoted.
Q30Alloys · Challenge · Paper 2 style · 6 marks
(a)A 250 g sample of brass contains 64 % copper by mass. Calculate the masses of copper and zinc in the sample.[2]
(b)Calculate the ratio of copper atoms to zinc atoms. Give your answer as x : 1 to 3 significant figures. (Ar: Cu = 64, Zn = 65)[2]
(c)Explain why brass is described as a mixture and not a compound.[2]
(c) The metals are not chemically combined in a fixed ratio; the composition of brass can vary (and it keeps the metallic properties of its components).
B1 not chemically bonded / no fixed formula; B1 variable composition.
Similar questions
Questions that test the same subtopic in different years, grouped so you can work on one skill at a time.
References only: find each question in its paper (official link where available, otherwise through your school).
Extraction of metalsBanker28 questions · 9/9 sessions
