Change of State and Latent Heat: JAMB Physics Questions, Answers & Notes

What Change of State and Latent Heat covers in the JAMB Physics syllabus

During a change of state, heat is absorbed or released at constant temperature — this is latent heat, found from Q = ml (l is specific latent heat, in J/kg). Latent heat of fusion melts a solid; latent heat of vaporisation boils a liquid; both are released in reverse (freezing, condensation). Evaporation occurs at all temperatures at the surface and causes cooling because energetic molecules escape; boiling occurs at a fixed temperature throughout. Sublimation is solid straight to vapour. Impurities raise water's boiling point, pressure raises it (pressure cooker) but lowers ice's melting point.

For Change of State and Latent Heat, JAMB expects you to be able to:

• Define latent heat of fusion and vaporisation and apply Q = ml
• Explain melting, boiling, evaporation, sublimation and condensation
• Explain cooling by evaporation and pressure/impurity effects on boiling and melting points

Key facts & revision notes: Change of State and Latent Heat

These are the recurring points our Change of State and Latent Heat questions test — revise them until each feels automatic, then practise the questions above to lock them in.

• Latent heat is the heat involved in a change of state at constant temperature.
• Latent heat of fusion is the heat needed to melt a solid at its melting point.
• Latent heat of vaporisation is the heat needed to boil a liquid at its boiling point.
• At the melting point, absorbed heat breaks bonds rather than raising temperature, so it stays constant.
• At a change of state, Q = ml, where l is the specific latent heat.
• Specific latent heat is measured in joules per kilogram (J/kg).
• Q = ml = 2 × 336000 = 672000 J.
• The most energetic molecules escape, lowering the average energy (and temperature) of the remaining liquid.
• A larger surface area, higher temperature and moving air all increase the rate of evaporation.
• Evaporation happens at any temperature and only at the surface; boiling occurs at a fixed temperature throughout.
• Sublimation is the direct change from solid to vapour (e.g.
• For ice, increased pressure lowers the melting point (ice melts under pressure) — a special case.
• Dissolved impurities raise the boiling point of water.
• Q = ml = 0.5 × 2260000 = 1130000 J.
• Higher pressure raises water's boiling point, so food cooks at a higher temperature and faster.
• Condensation is the reverse of vaporisation, so latent heat is released.
• Steam condensing on skin releases a large latent heat, causing a more severe burn than water alone.
• Latent heat changes molecular arrangement (breaking or forming bonds), not the temperature.
• High humidity slows the evaporation of sweat, so the body's cooling is reduced.
• The melting point is the temperature at which a solid becomes a liquid.
• Solid-to-liquid change involves the latent heat of fusion.
• Liquid-to-vapour change involves the latent heat of vaporisation.
• Q = ml = 3 × 3.36 × 10⁵ ≈ 1.01 × 10⁶ J.
• The temperature stays at the boiling point while latent heat is absorbed.

Worked examples

Three Change of State and Latent Heat questions with the answer and a short explanation, so you can see how the topic is set before you practise the full set.

How Change of State and Latent Heat is tested in JAMB Physics

Our Change of State and Latent Heat bank holds 40 questions (5 easy, 24 medium, 11 hard). JAMB Physics typically returns to Change of State and Latent Heat 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 Change of State and Latent Heat 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 Change of State and Latent Heat. 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 Physics 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 Change of State and Latent Heat is repeated timed practice, so use the button above until the recurring patterns feel automatic.

Common mistakes to avoid in Change of State and Latent Heat

The errors that cost marks on Change of State and Latent Heat 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 Change of State and Latent Heat actively by answering questions, not just by re-reading notes — recall under time is what the exam rewards.

Frequently asked questions

Is Change of State and Latent Heat part of the JAMB Physics syllabus?

Yes. Change of State and Latent Heat is a recognised topic in the JAMB Physics syllabus, covering define latent heat of fusion and vaporisation and apply Q = ml. You should be able to recall its key facts and apply them to multiple-choice questions.

How many Change of State and Latent Heat questions can I practise on Belmadeng?

There are 40 original, JAMB-standard Change of State and Latent Heat 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 Change of State and Latent Heat?

During a change of state, heat is absorbed or released at constant temperature — this is latent heat, found from Q = ml (l is specific latent heat, in J/kg). Latent heat of fusion melts a solid; latent heat of vaporisation boils a liquid; both are released in reverse (freezing, condensation). Evapor…

How do I answer Change of State and Latent Heat questions quickly in JAMB?

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

Are these JAMB Physics Change of State and Latent Heat 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 Change of State and Latent Heat questions free without signing up?

Right here — tap “Start Change of State and Latent Heat 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 Physics 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.