Energy Changes: JAMB Chemistry Questions, Answers & Notes

What Energy Changes covers in the JAMB Chemistry syllabus

Chemical reactions involve energy changes. Exothermic reactions release heat (surroundings warm, ΔH negative, products lower in energy); endothermic reactions absorb heat (surroundings cool, ΔH positive). The enthalpy change ΔH (kJ/mol) is the heat change at constant pressure. Breaking bonds absorbs energy and forming bonds releases it — the balance decides whether a reaction is exo- or endothermic. The activation energy is the minimum energy needed to react; a catalyst speeds a reaction by lowering activation energy without changing ΔH. Named enthalpy changes include heats of combustion (one mole burnt) and neutralisation (one mole of water formed).

For Energy Changes, JAMB expects you to be able to:

• Distinguish exothermic and endothermic reactions and the sign of ΔH
• Explain activation energy, bond energy and the role of a catalyst
• Define common enthalpy changes (combustion, neutralisation)

Key facts & revision notes: Energy Changes

These are the recurring points our Energy Changes questions test — revise them until each feels automatic, then practise the questions above to lock them in.

• An exothermic reaction releases heat (temperature of surroundings rises).
• An endothermic reaction absorbs heat (temperature of surroundings falls).
• The enthalpy change, ΔH, is the heat change at constant pressure.
• Exothermic reactions have a negative ΔH (heat is given out).
• Endothermic reactions have a positive ΔH (heat is absorbed).
• Combustion releases heat, so it is exothermic.
• Photosynthesis absorbs energy (light), so it is endothermic.
• The activation energy is the minimum energy needed for reactant particles to react.
• A catalyst provides an alternative path with lower activation energy.
• Heat of combustion is the enthalpy change when one mole of a substance burns completely.
• Heat of neutralisation is the enthalpy change for the formation of one mole of water from acid + base.
• In exothermic reactions, products have lower energy than reactants (energy released).
• Bond (dissociation) energy is the energy needed to break a particular bond.
• Bond breaking absorbs energy; bond forming releases energy.
• When bond formation releases more than bond breaking absorbs, net energy is given out — exothermic.
• The cooling shows heat is absorbed, so dissolving ammonium nitrate is endothermic.
• An energy profile diagram plots energy against reaction progress for reactants and products.
• A catalyst lowers activation energy and speeds the reaction but does not change ΔH.
• Enthalpy change is expressed in kilojoules per mole (kJ/mol).
• If the container feels cold, heat is being absorbed from the surroundings — endothermic.
• Exothermic reactions release heat, warming the surroundings.
• Endothermic reactions absorb heat, cooling the surroundings.
• Enthalpy change is written ΔH.
• Products have lower energy than reactants in an exothermic reaction.

Worked examples

Three Energy Changes questions with the answer and a short explanation, so you can see how the topic is set before you practise the full set.

How Energy Changes is tested in JAMB Chemistry

Our Energy Changes bank holds 40 questions (8 easy, 22 medium, 10 hard). JAMB Chemistry typically returns to Energy Changes year after year, so steady practice on this topic is high-value revision. Questions are multiple-choice with four options, and at UTME pace you get roughly 40 seconds each — which is why timed practice matters.

How to answer Energy Changes questions

Work the stem first and predict the answer before you look at the options; then eliminate the ones that contradict the key facts above. Watch for “which is not…”, “all of the above” and “except” style stems, which are where rushed candidates lose easy marks on Energy Changes. If a calculation or a precise definition is involved, work it from first principles rather than guessing from a half-remembered rule. When two options look right, re-read the stem for the qualifier that separates them — JAMB rarely repeats an option by accident. If you are still unsure, eliminate the two weakest choices to lift your odds, flag the question, and move on; never burn a full minute on one Chemistry item when the exam gives you about forty seconds each. Then come back to flagged questions with whatever time remains. The single most reliable way to get faster at Energy Changes is repeated timed practice, so use the button above until the recurring patterns feel automatic.

Common mistakes to avoid in Energy Changes

The errors that cost marks on Energy Changes are usually careless rather than conceptual: misreading a negative stem, confusing two similar terms, or rushing a definition you actually know. Candidates also over-rely on “expo” and last-minute cramming instead of understanding the topic — which fails the moment JAMB rephrases a familiar idea. Treat every option as a claim to be checked against the facts above, keep your working tidy for any calculation, and don’t change a considered answer on a hunch. Above all, revise Energy Changes actively by answering questions, not just by re-reading notes — recall under time is what the exam rewards.

Frequently asked questions

Is Energy Changes part of the JAMB Chemistry syllabus?

Yes. Energy Changes is a recognised topic in the JAMB Chemistry syllabus, covering distinguish exothermic and endothermic reactions and the sign of ΔH. You should be able to recall its key facts and apply them to multiple-choice questions.

How many Energy Changes questions can I practise on Belmadeng?

There are 40 original, JAMB-standard Energy Changes questions in our free bank, each with the correct answer and a worked explanation. You can practise them untimed or as a timed test.

What are the most important points to know about Energy Changes?

Chemical reactions involve energy changes. Exothermic reactions release heat (surroundings warm, ΔH negative, products lower in energy); endothermic reactions absorb heat (surroundings cool, ΔH positive). The enthalpy change ΔH (kJ/mol) is the heat change at constant pressure. Breaking bonds absorbs…

How do I answer Energy Changes questions quickly in JAMB?

Read the stem carefully, eliminate clearly wrong options, and match the remaining choices to the key facts for Energy Changes. Practising timed Energy Changes questions builds the speed you need for UTME's pace of about 40 seconds per question.

Are these JAMB Chemistry Energy Changes questions past questions or original?

They are original questions written to JAMB (UTME) standard and mapped to the official syllabus — not reproduced past papers. This keeps them legal to use freely while closely mirroring how the real exam tests the topic.

Where can I practise Energy Changes questions free without signing up?

Right here — tap “Start Energy Changes practice” on this page to begin instantly. Belmadeng's CBT practice is completely free and needs no sign-up, download or subscription.

About these questions: original, JAMB-standard items written from the official UTME Chemistry syllabus (last reviewed 2026-09-18). Belmadeng is an independent study platform and is not affiliated with JAMB. Spotted an error? Use the report link.