SPM Chemistry 2026: these 5 chapters are half of Paper 1

Every year the same question lands in the class group chat: "Which Chemistry chapters should I focus on?" So we did the boring part. We took 15 Chemistry trial papers from 2026 (13 states, plus MRSM and school papers), tagged every one of the 600 Paper 1 questions to its KSSM chapter and subtopic, and counted.

The result is clearer than we expected. Chemistry isn't evenly spread like Sejarah. A few chapters eat most of the paper, and one barely shows up at all.

The short answer

• 5 chapters cover 51% of the questions: Acids, Bases and Salts (F4), the Mole Concept (F4), Redox Equilibrium (F5), Rate of Reaction (F4) and Carbon Compounds (F5).
• Acids, Bases and Salts is the biggest: 12.4% of questions, about 5 per paper.
• The Mole Concept subtopic (F4 3.2) appeared in all 15 papers. It's the only subtopic at 100%.
• Form 4 carries more weight: 61% of questions come from Form 4, 39% from Form 5.
• Introduction to Chemistry (F4 Ch. 1) hardly appears: 1.2%, less than half a question per paper.

If you don't have much time left

A week left? Finish the top five chapters in the table below. Don't just reread notes: do at least one set of objective questions per chapter and work out why each wrong answer is wrong.

Three days left? Go after the "almost every paper" subtopics further down. They're small, and they turn up in 8 to 10 papers out of 10.

The night before? Don't open a new chapter. Go over the three things that carry the most marks and trip people up the most: mole calculations, the electrochemical series, and the sign of ΔH.

Every chapter, ranked (2026 trial papers)

"Qs/paper" is the average number of questions from that chapter in one 40-question paper.

The gap between first place (12.4%) and twelfth (6.3%) is almost double. In Chemistry, the order you revise in really does matter.

Subtopics that turn up in almost every paper

The count below is how many papers (out of every 10) had at least one question from that subtopic.

• F4 3.2 Mole Concept · 10 in 10 papers. Converting between number of particles, mass and gas volume. Remember 6.02 × 10²³ and a molar gas volume of 24 dm³ mol⁻¹ at room conditions.
• F5 3.2 Heat of Reaction · 9 in 10 papers. Usually a temperature change is given and you work out ΔH. Exothermic means a negative sign.
• F5 4.1 Polymers · 9 in 10 papers. Spotting the monomer from the polymer (and back), and natural versus synthetic polymers.
• F4 7.2 Factors Affecting Rate of Reaction · 9 in 10 papers. Particle size, concentration, temperature and catalyst. A full answer names the collision theory: the frequency of effective collisions.
• F5 2.3 Chemical Properties and Interconversion of Homologous Series · 9 in 10 papers. Alkane → alkene → alcohol → carboxylic acid → ester. Draw the conversion map once and the question patterns become obvious.
• F5 3.1 Heat Change in Reactions · 9 in 10 papers. Energy level diagram: products below reactants means exothermic.
• F4 3.3 Chemical Formulae · 8 in 10 papers. Empirical formula from percentage by mass: divide by relative atomic mass first, then find the simplest ratio.
• F5 1.1 Oxidation and Reduction · 8 in 10 papers. Oxidation number goes up means oxidation. The oxidising agent is the one that gets reduced.
• F5 1.3 Voltaic Cell · 8 in 10 papers. The more electropositive metal is the negative terminal (anode) and dissolves.
• F4 7.1 Determining Rate of Reaction · 8 in 10 papers. Initial rate = gradient of the tangent at t = 0 on the volume-against-time graph.

Mistakes we keep seeing

1. Molar volume. "Room conditions" means 24 dm³, "STP" means 22.4 dm³. Plenty of students use the wrong one because they didn't read the question to the end.
2. Mole ratio in titration. M₁V₁/M₂V₂ = a/b. For H₂SO₄ with NaOH the ratio is 1 : 2, not 1 : 1.
3. Insoluble salts. Learn the insoluble ones: all carbonates except Na, K and NH₄; PbSO₄, BaSO₄ and CaSO₄; PbCl₂ and AgCl. Every precipitation question depends on this list.
4. Heat of neutralisation for a weak acid. It's lower than 57 kJ mol⁻¹, because some of the heat goes into ionising the weak acid.
5. Electrochemical series upside down. Check which way round your series goes before you decide anode and cathode.

How we counted, and what it can't tell you

The data comes from 15 Chemistry Paper 1 trial papers from 2026 (state, MRSM and school papers) in Cerdek's question bank: 600 objective questions in all. Each question was matched to a subtopic of the KSSM Form 4 and 5 Chemistry textbooks. A question touching two subtopics counts as half for each, so everything still adds up to 100%.

A few things to keep in mind:

• These are trial papers, not real SPM papers. Teachers set them in the SPM format, so the pattern is useful, but it isn't a prediction of the questions.
• Paper 1 (objective) only. Paper 2 isn't included.
• 15 papers are enough to see the big picture, but a 0.5% gap between two chapters means nothing.

You can see the same analysis, by year and by form, in the Topic Insights feature of the Cerdek app.

Frequently asked questions

Which Chemistry chapter came up most in the 2026 SPM trial papers?

Acids, Bases and Salts (Form 4, Chapter 6), with 12.4% of questions, about 5 per Paper 1. Next were The Mole Concept, Chemical Formulae and Equations (10.8%) and Form 5 Redox Equilibrium (10.6%). This is based on 600 questions from 15 trial papers of 2026.

How many Chemistry chapters cover half of Paper 1?

Five: Acids, Bases and Salts; the Mole Concept; Redox Equilibrium; Rate of Reaction; and Carbon Compounds. Together they made up about 51% of the questions in the 2026 trial papers.

Which Chemistry subtopics are almost certain to come up?

The Mole Concept (F4 3.2) appeared in all 15 trial papers of 2026. Heat of Reaction, Polymers, Factors Affecting Rate of Reaction and Interconversion of Homologous Series each appeared in about 9 papers out of 10.

Is this the same as the real SPM questions?

No. It is based on state and school trial papers written in the SPM format. Use it to set your revision priorities, not to guess questions.