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Cambridge O Level

Chemistry 5070

The particulate nature of matter, bonding, reactions, the Periodic Table and organic chemistry for O Level candidates.

Syllabus version: 2026–2028 syllabusChecked against the Cambridge syllabusExam year 2027 is covered by the 2026–2028 syllabus.
Subject review complete (21 Oct 2026). All 40 Chemistry questions were re-solved and checked against the syllabus and Cambridge mark-scheme conventions, and their auto-marking was tested with correct and incorrect answers: 26 approved as written, 14 corrected.

Weighting by paper. Some papers are alternatives (for example Core or Extended, or practical or alternative to practical), so the figures add up to more than 100%.

  • Paper 1 Multiple Choice30%
  • Paper 2 Theory50%
  • Paper 3 Practical Test20%
  • Paper 4 Alternative to Practical20%
Original questions40
Topics covered12/12
Papers4
Mock papers3

What is assessed

4 components. Question formats: multiple choice, short answer, structured, practical, alternative to practical.

Paper 1 Multiple Choice
1 h40 marksWeighting 30%

40 compulsory four-option multiple-choice items on the whole syllabus, testing AO1 and AO2.

What the paper looks like

40 one-mark, four-option items in about syllabus order, answered in 1 hour with the Periodic Table supplied. Styles include single best answers, table rows (A–D), numbered statements (“1 and 2 only”) and short calculations (moles, gas volumes at r.t.p., concentrations, Rf values). Distractors are built from common errors, so work each item out before looking at the options.

Multiple choicePeriodic Table printed in the paper; calculator allowed
Checked against the Cambridge syllabus
Paper 2 Theory
1 h 45 min80 marksWeighting 50%

Compulsory short-answer and structured questions on the whole syllabus, testing AO1 and AO2.

What the paper looks like

About nine compulsory structured questions worth roughly 5 to 13 marks each (80 marks in 1 hour 45 minutes). The first is often a short “choose from the list” question. Parts use state, describe, explain, calculate, deduce and suggest, and ask for balanced equations with state symbols, dot-and-cross and displayed formulae, reaction pathway diagrams and multi-step calculations with significant figures specified. A Periodic Table is printed in the paper; calculators are allowed.

Short answerStructuredPeriodic Table printed in the paper; calculator allowed
Checked against the Cambridge syllabus
Paper 3 Practical Test
1 h 30 min40 marksWeighting 20%

Laboratory test of the experimental skills in section 4 (AO3); all items compulsory. Taken as an alternative to Paper 4.

What the paper looks like

A 1 hour 30 minute laboratory test (40 marks) in which you take and record your own readings. It usually contains a quantitative exercise (titration or temperature changes, with results compared with the supervisor’s), a qualitative analysis exercise recorded using the Notes for qualitative analysis, and a planning question of about 6 marks.

PracticalNotes for use in qualitative analysis provided; calculator allowed
Checked against the Cambridge syllabusNo questions for this paper yet
Paper 4 Alternative to Practical
1 h40 marksWeighting 20%

Written paper on the same experimental skills as Paper 3 (AO3), with no laboratory work; all items compulsory. Taken as an alternative to Paper 3.

What the paper looks like

A 1 hour written paper (40 marks, usually four questions) on the same skills as Paper 3, using readings, diagrams and observations supplied. Expect to name apparatus, read burettes and thermometers from diagrams, complete tables with consistent precision, choose concordant results, explain errors and improvements, draw conclusions from qualitative tests using the Notes provided, and write a structured plan of about 6 marks.

Alternative to practicalNotes for use in qualitative analysis provided; calculator allowed
Checked against the Cambridge syllabus

Assessment overview

From the 2026–2028 syllabus. Checked against the Cambridge syllabus

All candidates
Paper 1Paper 2Paper 3Paper 4
Papers 1 and 2, plus either Paper 3 (Practical Test) or Paper 4 (Alternative to Practical). Grades A* to E.
Assessment objectiveO Level weighting
AO1 Knowledge with understanding50%
AO2 Handling information and problem-solving30%
AO3 Experimental skills and investigations20%
Changes in this syllabus version
  • Version 1, published September 2023: Cambridge states there are no substantial changes that affect teaching compared with the 2023–2025 syllabus.
  • Same assessment structure: Paper 1 (1 hour, 40 marks, 30%), Paper 2 (1 hour 45 minutes, 80 marks, 50%), and either Paper 3 Practical Test (1 hour 30 minutes) or Paper 4 Alternative to Practical (1 hour), each 40 marks, 20%.
  • The “Equality and inclusion” section has been rewritten as “Accessibility and equality”.
  • Textbooks endorsed for examination from 2023 remain suitable.
Command words used in Chemistry papers (23)
Analyse
Look at something in detail to show what it means and how its parts relate to each other.
Calculate
Work out a value from the facts, figures or data given.
Compare
Point out the similarities and/or differences.
Consider
Think about the information given and respond to it.
Contrast
Point out the differences.
Deduce
Reach a conclusion from the information provided.
Define
Give the exact meaning.
Demonstrate
Show how, or give an example.
Describe
Give the main points or characteristics of something.
Determine
Find an answer using the information available.
Discuss
Write about an issue or topic in depth, in an organised way.
Evaluate
Judge or work out the quality, importance, amount or value of something.
Examine
Look into something closely and in detail.
Explain
Give reasons or purposes, make relationships clear, and support them with evidence.
Give
Produce an answer from a source or from memory.
Identify
Name, select or recognise.
Justify
Back up a case or decision with evidence or argument.
Outline
Set out the main points only.
Predict
Say what is likely to happen, based on the information given.
Show (that)
Give a structured series of steps that leads to the stated result.
Sketch
Make a simple freehand drawing showing the key features, with sensible proportions.
State
Say something clearly and briefly.
Suggest
Apply what you know to a situation where several answers are possible, putting forward ideas.
Examiner guidance from recent reports (14)
Stoichiometry. Set out mole calculations step by step (mass → moles → ratio → answer) so credit can be carried forward from a slip. Convert cm³ to dm³ by dividing by 1000, multiply moles of gas by 24 (do not divide), use the mole ratio from the equation rather than assuming 1 : 1, and round only the final answer to the number of significant figures asked.
Chemical reactions. In equilibrium answers say that the position of equilibrium moves to the left or right; “the reaction moves” or “favours the right” loses credit. Name which direction is exothermic (e.g. “the forward reaction is exothermic”) and, for pressure, compare the numbers of moles of gas on each side.
Chemical reactions. Collision-theory answers need particles in every sentence: higher concentration means more particles per unit volume, so collisions are more frequent; higher temperature means particles have more kinetic energy, so collisions are more frequent and a greater proportion of them have energy equal to or above the activation energy. “More collisions” alone is not enough.
Chemical energetics. Energy is absorbed to break bonds and released when bonds form; never write that energy is needed to make bonds. On a reaction pathway diagram, draw the ΔH arrow from the reactant line to the product line and the Ea arrow from the reactant line to the top of the curve, with clear arrowheads in the right direction.
Atoms, elements and compounds. Be precise about particles: a magnesium atom loses two electrons; each fluorine atom (or a fluorine molecule) gains electrons. For high melting points of ionic compounds describe strong attraction between oppositely charged ions needing a lot of energy to overcome; never mention intermolecular forces for ionic or giant covalent substances.
Organic chemistry. A displayed formula must show every atom and every bond, including the O–H bond in alcohols and acids. When naming esters, the acid part includes the carbon of the –COO– group (CH₃CH₂CH₂COOCH₃ is methyl butanoate). Spell names exactly and give formulae when a formula is asked for.
Organic chemistry. Addition polymerisation uses unsaturated monomers (C=C) and forms the polymer only; condensation polymerisation uses monomers with two functional groups and also forms a small molecule such as water. Environmental answers about plastics need specifics such as non-biodegradable waste in landfill, build-up in oceans harming marine life, or toxic gases from burning.
Acids, bases and salts. To find pH, put a drop of solution on universal indicator paper and compare the colour with a pH colour chart; litmus and methyl orange do not give a pH value. Colour changes need both the starting and the final colour. Check formulae before balancing: HNO₃(aq), Zn(NO₃)₂(aq), H₂O(l).
Chemistry of the environment. Greenhouse gases absorb thermal (infrared) energy emitted from the Earth and re-emit it, reducing energy lost to space; this is not about the ozone layer. Sulfur dioxide comes from sulfur compounds in fossil fuels and is removed by flue gas desulfurisation or avoided with low-sulfur fuels; catalytic converters do not remove sulfur dioxide.
Experimental techniques and chemical analysis. Use the Notes for qualitative analysis and quote them exactly: “white ppt., insoluble in excess”. An observation is what you see (effervescence, bubbles), not a conclusion (carbon dioxide made). Dilute nitric acid is added before silver nitrate or barium nitrate to stop other ions such as carbonate giving a precipitate. In a flame test only the first colour counts.
Experimental techniques and chemical analysis. Record readings to the precision of the apparatus and keep it consistent: burette readings to 1 decimal place (0.0, not 0), thermometer readings to the nearest 0.5 °C (20.0, not 20). Read the stem carefully: subtract the initial burette reading, rinse a burette with the solution it will hold, and in planning answers cover apparatus, method, accuracy (repeat, constant mass) and the calculation.
Metals. When results are temperature rises, explain the order with the data: the greater the temperature rise, the more reactive the metal. If measured rises are too low, the reason is heat loss to the surroundings and the fix is insulation or a lid. For sacrificial protection say the more reactive metal loses electrons (is oxidised) instead of iron.
Electrochemistry. Metals or hydrogen form at the cathode and non-metals other than hydrogen at the anode. With copper electrodes in copper(II) sulfate the anode dissolves and the solution stays blue; with graphite electrodes oxygen bubbles at the anode and the blue colour fades. Write half-equations with electrons on the correct side.
The Periodic Table. Use halogen and halide carefully: bromine (Br₂) displaces iodide ions (I⁻) to form iodine, and the solution turns brown. When predicting properties from a table of data, place the new value within the trend shown and give a value, not just “higher” or “lower”.

Topic map

Practice types

Free sample questions

A long glass tube contains air. A small sample of one gas is released at one end and the time taken for it to…
A long glass tube contains air. A small sample of one gas is released at one end and the time taken for it to be detected at the other end is measured. The test is repeated with each of four gases, at the same temperature and pressure.
Which gas is detected first?
[Ar: H, 1; C, 12; N, 14; O, 16; Cl, 35.5]
  1. carbon monoxide, CO
  2. chlorine, Cl2
  3. methane, CH4
  4. nitrogen dioxide, NO2

Answer: C. methane, CH4

At the same temperature, particles with a lower relative molecular mass move faster on average, so they diffuse faster. Mr: CH₄ = 16, CO = 28, NO₂ = 46, Cl₂ = 71. Methane has the lowest Mr, so it arrives first. Chlorine (the most familiar gas) is the slowest.

The symbol for an ion is 3416S2−. How many protons, neutrons and electrons are in this ion?
The symbol for an ion is 3416S2−.
How many protons, neutrons and electrons are in this ion?
  1. 16 protons, 18 neutrons, 18 electrons
  2. 16 protons, 18 neutrons, 14 electrons
  3. 16 protons, 34 neutrons, 18 electrons
  4. 18 protons, 16 neutrons, 16 electrons

Answer: A. 16 protons, 18 neutrons, 18 electrons

Proton number 16, so 16 protons. Neutrons = nucleon number − proton number = 34 − 16 = 18. A 2− charge means two electrons have been gained: 16 + 2 = 18 electrons. Subtracting the charge (14 electrons) is the usual slip; 34 is the nucleon number, not the number of neutrons.

FAQs

Are these official 5070 past-paper questions?

No. They are original questions written to match the Chemistry syllabus topics. Official past papers are available to schools through Cambridge.

Why choose an exam year?

Cambridge updates syllabuses periodically. Your exam year selects the matching configuration so topics and components follow the right version.

Is a calculator allowed?

In this configuration a scientific calculator is permitted for the listed papers. Check your syllabus for the exact rule.