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Practice paper written from an analysis of every
O-Level Science (Chemistry) paper, 2010–2025
Paper 3 Chemistry
FORECAST PAPER · PAPER 3.10
For practice before the 2026 examination
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.
Write your name, centre number and index number in the boxes above.
You may use an HB pencil for any diagrams, graphs or rough working.
Write in dark blue or black pen.
Do not use staples, paper clips, glue or correction fluid.
The use of an approved scientific calculator is expected, where appropriate.
You may lose marks if you do not show your working or if you do not use appropriate units.
Section A
Answer all questions.
Write your answers in the spaces provided on the question paper.
Section B
Answer one question.
Write your answers in the spaces provided on the question paper.
A copy of the Data Sheet is printed on page 16.
A copy of the Periodic Table is printed on page 17.
The number of marks is given in brackets [ ] at the end of each question or part question.
The total mark for this paper is 65.
A health inspector checks the coloured coating of tablets that are sold online. The dyes in each coating are separated by paper chromatography.
Fig. 1.1 shows the chromatogram of the coating of a genuine tablet, G, of a banned dye, B, and of the coatings of three tablets, J, K and L, that were sold online.
Identify the tablet that has a coating with the same dyes as the genuine tablet.
Identify the tablet that contains the banned dye B.
The start line was drawn on the chromatography paper in pencil, not in ink.
Explain why.
Hospitals store medical oxygen as a liquid at very low temperature. The oxygen is supplied to wards as a gas, in cylinders at high pressure.
Fig. 2.1 shows the particles of oxygen in a sample of the gas, A, in the same gas after it has been compressed, B, and in liquid oxygen, C.
Name the change of state that happens when oxygen gas is cooled until it becomes liquid oxygen.
Use Fig. 2.1 to explain why the oxygen gas in A can be compressed to give B, but liquid oxygen C cannot be compressed.
Liquid oxygen in a storage tank slowly changes to a gas as it takes in energy from the surroundings.
Explain what happens to the oxygen particles as this change takes place.
Use ideas about energy and forces between particles in your answer.
Fireworks contain compounds that give coloured flames and substances that burn. Strontium chloride, SrCl2, gives a red flame. It melts at 874 °C. It does not conduct electricity when solid but it does conduct when molten. Sulfur is a fuel in fireworks. It melts at 115 °C and does not conduct electricity when solid or when molten.
Strontium chloride is an ionic compound.
Describe what is meant by the term ionic bond.
Use ideas about structure and bonding to explain why strontium chloride has a high melting point.
Explain why sulfur does not conduct electricity when it is molten.
Barium chloride, BaCl2, gives a green flame. Barium is a metal.
Predict whether barium chloride conducts electricity when it is solid and when it is molten.
Explain your prediction.
Lettuce is grown on a space station in trays of water that contain dissolved nutrients. The solution must have a pH between 5.5 and 6.5 for the plants to grow well.
Table 4.1 shows the pH of the solution in one tray over 28 days.
| time / days | pH of the solution |
|---|---|
| 0 | 6.2 |
| 7 | 5.9 |
| 14 | 5.4 |
| 21 | 4.8 |
| 28 | 4.2 |
Use Table 4.1 to describe how the pH of the solution changes with time.
State the day on which the pH of the solution first falls below the range that the plants need.
The astronauts add aqueous potassium hydroxide to neutralise the nitric acid that has formed in the solution.
Name the salt that is formed in this reaction.
The astronauts do not add any potassium hydroxide.
Predict the pH of the solution on day 35. Give a reason for your answer.
Some breakfast cereals contain iron powder. Iron reacts with the hydrochloric acid in the stomach.
A student models this reaction. In experiment 1, 0.28 g of iron powder is added to 25 cm3 of dilute hydrochloric acid of concentration 1.0 mol / dm3 at 20 °C. Experiment 2 is the same, except that 0.28 g of iron in small pieces is used instead of powder. The hydrogen formed is collected in a gas syringe.
Table 5.1 shows the volume of hydrogen collected in each experiment.
| time / s | volume of hydrogen with iron powder / cm3 | volume of hydrogen with small pieces of iron / cm3 |
|---|---|---|
| 0 | 0 | 0 |
| 30 | 36 | 12 |
| 60 | 62 | 22 |
| 90 | 82 | 31 |
| 120 | 96 | 39 |
Calculate the average rate of reaction in the first 30 s of experiment 1.
State which experiment has the higher rate of reaction.
Give a reason for your answer, using data from Table 5.1.
Explain, in terms of particles, why the iron powder reacts at a higher rate than the small pieces of iron.
A hand warmer is a pack that contains iron powder. The iron powder reacts slowly with oxygen in the air (it rusts) and the pack becomes warm.
Name the type of energy change in this reaction.
A school holds a sports festival. A firework display ends the festival, and a generator that burns bioethanol supplies power for the lights.
Fig. 6.1 shows three gases that are released into the air during the day, some sources of gases and some effects of gases.
Draw one line from each gas to its main source and one line from each gas to its effect.
Draw six lines in total.
Bioethanol is a biofuel.
Table 6.1 shows some statements about bioethanol.
Tick the two statements that are correct.
| statement | tick (✓) |
|---|---|
| It is made by fermenting the sugar in sugar cane. | |
| It is made by the fractional distillation of crude oil. | |
| It is the main compound in natural gas. | |
| It can be burnt as a fuel in engines. | |
| It is a hydrocarbon. |
Three colourless solutions, X, Y and Z, are tested in a laboratory that checks food additives and health products. The solutions are zinc sulfate, aluminium nitrate and ammonium nitrate, but not in that order.
Plan an experiment to show which solution is which. You may use only aqueous sodium hydroxide and aqueous ammonia.
Describe what you would do and the results you would expect for each solution.
A student uses only aqueous sodium hydroxide.
Explain why the student cannot tell which solution is zinc sulfate and which is aluminium nitrate.
A technician tests a white solid, R, which is a sodium compound used as a food additive. Fig. 7.1 shows the tests.
Identify precipitate S and the anion in solid R.
Write a balanced chemical equation, including state symbols, for the reaction of aqueous R with aqueous barium nitrate.
Dinitrogen oxide is a gas that dentists use to reduce pain. It is made by heating ammonium nitrate.
Table 8.1 shows the number of atoms of each element in one molecule of dinitrogen oxide.
| nitrogen | oxygen | |
|---|---|---|
| number of atoms in one molecule | 2 | 1 |
Use Table 8.1 to calculate the relative molecular mass, Mr, of dinitrogen oxide.
A dental supplier heats 2.0 kg of ammonium nitrate. Calculate the amount, in moles, of ammonium nitrate in this mass.
Use your answer to (b) and the equation to calculate the volume of dinitrogen oxide formed, at room temperature and pressure.
Calculate the mass of dinitrogen oxide formed from the 2.0 kg of ammonium nitrate.
A solution of ammonium nitrate has a concentration of 0.200 mol / dm3.
Calculate the mass of ammonium nitrate that is needed to make 500 cm3 of this solution.
Hospitals use ethanol in hand sanitiser. Ethanol is an alcohol. It can be made from the sugar glucose by fermentation.
Methanol is the first member of the alcohols. Draw its displayed formula, showing all the atoms and all the bonds.
Write the molecular formula of ethanol.
A student plans to make ethanol from glucose. The plan is shown below.
The plan has three mistakes. Identify each mistake and state how it should be corrected.
Write a balanced equation for the fermentation of C6H12O6 to ethanol and carbon dioxide.
Ethanol burns in a limited supply of oxygen.
Name two products of this reaction, other than carbon dioxide.
Ethanol can also be made from ethene, C2H4, which is unsaturated.
State what is meant by the term unsaturated. Name the type of reaction that ethene can take part in with bromine or hydrogen because it is unsaturated.
Potassium iodide is added to some food supplements to provide iodine for the body. Iodine is a halogen in Group 17.
Five halogens, A, B, C, D and E, are listed in order of decreasing reactivity, starting with the most reactive. At room temperature, A and B are gases and C is a liquid. The letters are not the chemical symbols.
Use the Periodic Table to complete Table 10.1.
| property | answer |
|---|---|
| state of E at room temperature | |
| formula of a molecule of B | |
| formula of the compound formed when D reacts with potassium |
A technician tests a solution made from a supplement that contains potassium iodide. Chlorine is bubbled through the solution until the reaction is complete. Chlorine is not in excess. Fig. 10.1 shows the particles in the mixture before the reaction and four possible diagrams of the mixture after the reaction. The water is not shown.
Fig. 10.2 shows the electron arrangement in an atom of fluorine and an incomplete diagram of an atom of chlorine. Complete Fig. 10.2 by drawing crosses to show the electron arrangement in an atom of chlorine.
Use Table 10.2 to describe how the colour of the halogens changes down Group 17.
| halogen | proton number | colour | state at room temperature |
|---|---|---|---|
| fluorine | 9 | pale yellow | gas |
| chlorine | 17 | pale green | gas |
| bromine | 35 | red-brown | liquid |
| iodine | 53 | grey-black | solid |
Astatine, At, is below iodine in Group 17. Astatine has proton number 85.
Predict the colour of astatine.
Predict the number of electrons in the outer shell of an atom of astatine. Explain how you decided.
Hydrogen and fluorine are used as fuel and oxidiser in some experimental rocket engines. Fluorine exists as molecules, F2, in which the two atoms are joined by a covalent bond. Fig. 10.3 shows an outline of a molecule of fluorine. Complete Fig. 10.3 to show all the electrons in a molecule of fluorine. Use dots and crosses. The small circle round each F is its first shell.
Hydrogen reacts with fluorine in the rocket engine. The equation for the reaction is shown.
Rocks on the Moon contain compounds of metals such as magnesium and iron.
A student compares the reactivity of three metals, magnesium, zinc and iron. The student adds a piece of each metal, one at a time, to dilute hydrochloric acid and measures the volume of hydrogen collected. Table 11.1 shows the results.
| metal | volume of hydrogen collected after 20 s / cm3 | volume of hydrogen collected after 40 s / cm3 | volume of hydrogen collected after 60 s / cm3 | average rate of production of hydrogen, in the first 20 s / cm3 per s |
|---|---|---|---|---|
| magnesium | 38 | 52 | 60 | 1.9 |
| zinc | 8 | 14 | 18 | |
| iron | 3 | 5 | 7 | 0.15 |
The student wants the comparison to be a fair test. State two variables that the student must keep the same in each experiment.
Calculate the average rate of production of hydrogen by zinc in the first 20 s. Complete the last column of Table 11.1 for zinc.
Use the average rates in Table 11.1 to deduce the order of reactivity of the three metals. Start with the most reactive.
The student also adds a piece of copper to the acid. No bubbles are seen. State where copper is placed in the reactivity series compared with hydrogen.
The student looks more closely at the results.
The student repeats the experiment once for each metal and gets slightly different volumes. Suggest one way to make the results more reliable.
Use Table 11.1 to estimate the volume of hydrogen made by zinc at 30 s.
Magnesium reacts with dilute hydrochloric acid to form magnesium chloride, MgCl2, an ionic compound. Fig. 11.1 shows a partly drawn 'dot-and-cross' diagram of magnesium chloride. Complete Fig. 11.1 by adding the missing electrons and the charge on each ion. Show only the outer shell electrons.
Iron in Moon rock reacts with dilute hydrochloric acid. The ionic equation for the reaction is shown.
| aluminium hydroxide | white |
| calcium hydroxide | white |
| copper(II) hydroxide | light blue |
| iron(II) hydroxide | green |
| iron(III) hydroxide | red-brown |
| zinc hydroxide | white |
Group | |||||||||||||||||
1 | 2 |
| 13 | 14 | 15 | 16 | 17 | 18 | |||||||||
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| 1 H hydrogen 1 |
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| 2 He helium 4 | ||
3 Li lithium 7 | 4 Be beryllium 9 |
| proton (atomic) number atomic symbol name relative atomic mass |
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| 5 B boron 11 | 6 C carbon 12 | 7 N nitrogen 14 | 8 O oxygen 16 | 9 F fluorine 19 | 10 Ne neon 20 | ||
11 Na sodium 23 | 12 Mg magnesium 24 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 Al aluminium 27 | 14 Si silicon 28 | 15 P phosphorus 31 | 16 S sulfur 32 | 17 Cl chlorine 35.5 | 18 Ar argon 40 |
19 K potassium 39 | 20 Ca calcium 40 | 21 Sc scandium 45 | 22 Ti titanium 48 | 23 V vanadium 51 | 24 Cr chromium 52 | 25 Mn manganese 55 | 26 Fe iron 56 | 27 Co cobalt 59 | 28 Ni nickel 59 | 29 Cu copper 64 | 30 Zn zinc 65 | 31 Ga gallium 70 | 32 Ge germanium 73 | 33 As arsenic 75 | 34 Se selenium 79 | 35 Br bromine 80 | 36 Kr krypton 84 |
37 Rb rubidium 85 | 38 Sr strontium 88 | 39 Y yttrium 89 | 40 Zr zirconium 91 | 41 Nb niobium 93 | 42 Mo molybdenum 96 | 43 Tc technetium – | 44 Ru ruthenium 101 | 45 Rh rhodium 103 | 46 Pd palladium 106 | 47 Ag silver 108 | 48 Cd cadmium 112 | 49 In indium 115 | 50 Sn tin 119 | 51 Sb antimony 122 | 52 Te tellurium 128 | 53 I iodine 127 | 54 Xe xenon 131 |
55 Cs caesium 133 | 56 Ba barium 137 | 57–71 lanthanoids
| 72 Hf hafnium 178 | 73 Ta tantalum 181 | 74 W tungsten 184 | 75 Re rhenium 186 | 76 Os osmium 190 | 77 Ir iridium 192 | 78 Pt platinum 195 | 79 Au gold 197 | 80 Hg mercury 201 | 81 Tl thallium 204 | 82 Pb lead 207 | 83 Bi bismuth 209 | 84 Po polonium – | 85 At astatine – | 86 Rn radon – |
87 Fr francium – | 88 Ra radium – | 89–103 actinoids
| 104 Rf rutherfordium – | 105 Db dubnium – | 106 Sg seaborgium – | 107 Bh bohrium – | 108 Hs hassium – | 109 Mt meitnerium – | 110 Ds darmstadtium – | 111 Rg roentgenium – | 112 Cn copernicium – | 113 Nh nihonium – | 114 Fl flerovium – | 115 Mc moscovium – | 116 Lv livermorium – | 117 Ts tennessine – | 118 Og oganesson – |
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lanthanoids | 57 La lanthanum 139 | 58 Ce cerium 140 | 59 Pr praseodymium 141 | 60 Nd neodymium 144 | 61 Pm promethium – | 62 Sm samarium 150 | 63 Eu europium 152 | 64 Gd gadolinium 157 | 65 Tb terbium 159 | 66 Dy dysprosium 163 | 67 Ho holmium 165 | 68 Er erbium 167 | 69 Tm thulium 169 | 70 Yb ytterbium 173 | 71 Lu lutetium 175 |
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actinoids | 89 Ac actinium – | 90 Th thorium 232 | 91 Pa protactinium 231 | 92 U uranium 238 | 93 Np neptunium – | 94 Pu plutonium – | 95 Am americium – | 96 Cm curium – | 97 Bk berkelium – | 98 Cf californium – | 99 Es einsteinium – | 100 Fm fermium – | 101 Md mendelevium – | 102 No nobelium – | 103 Lr lawrencium – |
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The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
The Avogadro constant, L = 6.02 × 1023 mol-1