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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 3.3
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.
Fig. 1.1 shows three set-ups, A, B and C, that are used to collect or measure gases. In each set-up the delivery tube is joined to the apparatus in which the gas is made.
Ammonia is less dense than air and is very soluble in water.
Write the letter of the set-up that is suitable for collecting a sample of ammonia. Give a reason for your answer.
Sulfur dioxide is very soluble in water.
Write the letter of the set-up that is suitable for measuring the volume of sulfur dioxide formed in an experiment. Give a reason for your answer.
Carbon monoxide is insoluble in water. Its density is almost the same as the density of air.
Write the letter of the set-up that is suitable for collecting a sample of carbon monoxide. Give a reason for your answer.
Helium is a gas that is less dense than air. It is used to fill party balloons. Table 2.1 shows information about the particles in an atom.
| particle | relative mass | relative charge |
|---|---|---|
| proton | 1 | +1 |
| neutron | 1 | |
| electron | −1 |
Complete Table 2.1.
Helium-3 is a rare form of helium. An atom of helium-3 is written as 32He.
State the number of neutrons in one atom of helium-3.
State the number of electrons in one atom of helium-3.
Substances can be classified as elements, compounds or mixtures.
Each box, A, B and C, describes a different sample.
Write element, compound or mixture on each line.
Aluminium atoms form aluminium ions, Al3+.
Describe how an aluminium atom forms an aluminium ion.
Aluminium is a metal.
State one general physical property of metals.
Fig. 4.1 shows the ions in the water in three beakers, A, B and C. Each beaker holds a different solution. Beaker D has no ions drawn in it.
Identify the beaker that contains a solution with a pH of 7.
Identify the beaker that contains the most alkaline solution.
Identify the beaker that contains the most acidic solution.
Dilute acid is added to the solution in beaker C until the solution is neutral. Beaker D shows this neutral solution.
Draw H+ ions and OH− ions in beaker D in Fig. 4.1 to show the ions in the neutral solution.
Beaker B contains dilute hydrochloric acid. Magnesium ribbon is added to the solution in beaker B.
State the name of the gas that is formed.
Marble chips are mostly calcium carbonate. They react with dilute hydrochloric acid to form carbon dioxide.
A student adds 0.50 g of marble chips to an excess of dilute hydrochloric acid at 22 °C and collects the carbon dioxide in a gas syringe. The student does this once with large chips and once with small chips. The same mass of marble and the same volume and concentration of acid are used each time. Table 5.1 shows the volume of gas in the syringe every 20 s.
| time / s | volume of carbon dioxide with large chips / cm3 | volume of carbon dioxide with small chips / cm3 |
|---|---|---|
| 0 | 0 | 0 |
| 20 | 47 | 97 |
| 40 | 76 | 116 |
| 60 | 93 | 119 |
| 80 | 104 | 120 |
| 100 | 110 |
Complete Table 5.1 for the small chips at 100 s.
Small marble chips react at a higher rate than large marble chips.
Explain why, in terms of particles.
Describe how the student can tell that the reaction has finished.
A thermometer in the acid shows that the temperature rises from 22.0 °C to 23.0 °C during the reaction.
State whether the reaction is exothermic or endothermic. Give a reason for your answer.
Rubbish buried in a landfill site decays without air to form biogas. Biogas contains methane and can be burnt as a fuel. Five students, A to E, make statements about biogas.
Student A says: “Methane is a greenhouse gas.”
State whether the student is correct. If the student is not correct, write the correct statement.
Student B says: “Burning the methane in biogas produces carbon dioxide, so collecting biogas does not help to reduce global warming.”
State whether the student is correct. If the student is not correct, write the correct statement.
Student C says: “Photosynthesis in plants adds carbon dioxide to the air.”
State whether the student is correct. If the student is not correct, write the correct statement.
Student D says: “Biogas is a renewable fuel because the waste that it is made from is produced all the time.”
State whether the student is correct. If the student is not correct, write the correct statement.
Student E says: “Burning biogas adds no carbon dioxide to the air.”
State whether the student is correct. If the student is not correct, write the correct statement.
Fig. 7.1 shows some reactions of the solid R and of the solution T.
Identify each of R, S, T, U, V, W and X.
You may give the name or the formula of each.
Write a balanced chemical equation, including state symbols, for any one of the reactions shown in Fig. 7.1.
Ammonia can be made in the laboratory by heating ammonium chloride with calcium hydroxide.
Calculate the relative formula mass, Mr, of ammonium chloride, NH4Cl.
A student heats 4.28 g of ammonium chloride with calcium hydroxide.
Calculate the amount, in moles, of ammonium chloride in 4.28 g.
Use your answer to (b) and the equation to calculate the minimum mass of calcium hydroxide needed to react completely with the ammonium chloride.
Calculate the volume of ammonia gas, at room temperature and pressure, formed from 4.28 g of ammonium chloride.
All of the ammonia is dissolved in water to make 500 cm3 of solution.
Calculate the concentration of the ammonia solution in mol / dm3.
Use your answer to (e) to calculate the concentration of the ammonia solution in g / dm3.
Alcohols form a homologous series. Table 9.1 shows information about the first three alcohols.
| name | number of carbon atoms | formula | boiling point / °C |
|---|---|---|---|
| methanol | 1 | CH3OH | 65 |
| ethanol | 2 | 78 | |
| 3 | C3H7OH | 97 |
Complete Table 9.1.
Draw the displayed formula of the alcohol with three carbon atoms in Table 9.1.
Show all the atoms and all the bonds.
Use data from Table 9.1 to describe the trend in the boiling points of the alcohols as the number of carbon atoms increases.
Ethanol burns in excess oxygen.
Write a balanced chemical equation for this reaction.
Ethanol can be oxidised to form an acid.
State the name of an oxidising agent that can be used for this reaction.
State the name of the acid that is formed when ethanol is oxidised.
Margarine is made from vegetable oils.
A student adds aqueous bromine to 5.0 g of each of three vegetable oils until the orange colour no longer disappears. The aqueous bromine has the same concentration each time. Table 9.2 shows the volume of aqueous bromine that was decolourised by each oil.
| vegetable oil | volume of aqueous bromine decolourised / cm3 |
|---|---|
| coconut oil | 0.8 |
| olive oil | 4.5 |
| sunflower oil | 7.5 |
Identify the oil that is the most unsaturated.
Give a reason for your answer.
Explain why an unsaturated oil decolourises aqueous bromine.
Use ideas about structure in your answer.
Fig. 9.1 shows the displayed formula of propenenitrile. It forms the addition polymer poly(propenenitrile).
Fig. 9.2 shows four repeat units, A, B, C and D. The nitrile group is written as CN.
Identify the repeat unit that is in poly(propenenitrile).
The reactions of metals with water and with dilute acid depend on the position of the metal in the reactivity series.
Table 10.1 shows whether bubbles of gas are produced when pieces of four metals are added to cold water and to dilute hydrochloric acid. The metals are listed in order of reactivity, starting with the most reactive. Some of the results are missing.
| metal | cold water | dilute hydrochloric acid |
|---|---|---|
| sodium | bubbles produced | not tested (too dangerous) |
| calcium | ||
| iron | no bubbles | |
| copper | no bubbles |
Complete Table 10.1. Write bubbles or no bubbles in each of the four empty boxes.
Magnesium reacts rapidly with dilute hydrochloric acid but only very slowly with cold water. State which two metals in Table 10.1 magnesium lies between in the reactivity series.
Choose from the metals listed the one that can be obtained from its oxide by heating the oxide with carbon.
Fig. 10.1 shows an experiment with damp iron wool. The iron wool is wedged at the closed end of a tube that contains air at the start. After one week, the iron wool has rusted. Deduce which gas in the air reacted with the iron. Use data from Fig. 10.1 to explain your answer.
Calcium reacts with cold water. Name the two products of this reaction.
Calcium reacts with fluorine to form calcium fluoride, an ionic compound found in nature as the mineral fluorite. Draw a 'dot-and-cross' diagram to show the bonding in calcium fluoride. Show only the outer shell electrons. Include the charge on each ion.
Rust is mainly iron(III) oxide. The rusting of iron wool can be represented by the equation shown.
The halogens in Group 17 are reactive non-metals.
A student heats iron wool and places it in the vapour of each of three halogens in turn. The mass of iron wool and the temperature are the same in each experiment. Table 11.1 shows the observations.
| halogen | observations when hot iron wool is placed in the halogen vapour | order of reactivity (1 = most reactive) |
|---|---|---|
| chlorine | the iron wool glows brightly at once; a brown solid forms | |
| bromine | the iron wool glows dimly after some time; a brown solid forms slowly | |
| iodine | the iron wool glows faintly only after strong heating; a small amount of solid forms very slowly |
Complete the last column of Table 11.1. Write 1, 2 or 3 in each box.
Table 11.2 shows the melting points and boiling points of four halogens. The melting point of bromine is missing. Predict a value for the melting point of bromine.
| halogen | melting point / °C | boiling point / °C |
|---|---|---|
| fluorine | −220 | −188 |
| chlorine | −101 | −34 |
| bromine | 59 | |
| iodine | 114 | 184 |
Use Table 11.2 to deduce the physical state of chlorine at room temperature (25 °C). Give a reason for your answer.
Sodium and chlorine are in the same period of the Periodic Table. Sodium has the electronic configuration 2.8.1 and chlorine has 2.8.7. Explain, in terms of outer shell electrons, why sodium is a metal and chlorine is a non-metal.
State the number of occupied electron shells in an atom of fluorine and in an atom of chlorine.
Ammonia, NH3, is a covalent compound formed when nitrogen reacts with hydrogen. Draw a 'dot-and-cross' diagram to show the bonding in a molecule of ammonia. Show only the outer shell electrons.
Sodium reacts with bromine. The equation for the reaction is shown.
| statement | tick (✓) |
|---|---|
| bromine is oxidised | |
| bromine is reduced | |
| bromine is neither oxidised nor reduced |
| 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