Exothermic and Endothermic Reactions Exam Questions
Practice IGCSE Chemistry exam questions on exothermic and endothermic reactions. Covers definitions, identifying reaction types from temperature changes, examples of each, and energy changes in chemical reactions with mark schemes and examiner notes.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
These questions cover exothermic and endothermic reactions. Write full answers before checking.
Question 1 (2 marks, Core)
Define the terms exothermic reaction and endothermic reaction.
Mark scheme
- Exothermic: a reaction that releases/gives out heat energy to the surroundings / the temperature of the surroundings increases [1]
- Endothermic: a reaction that takes in / absorbs heat energy from the surroundings / the temperature of the surroundings decreases [1]
Examiner note: Do not confuse the system and the surroundings. In an exothermic reaction, the temperature of the mixture (surroundings) rises because energy is released. Saying “the temperature increases” without specifying what is insufficient.
Question 2 (3 marks, Core)
A student adds magnesium ribbon to dilute hydrochloric acid in a polystyrene cup and records the temperature every 30 seconds. The temperature rises from 22 degC to 45 degC.
(a) State whether this reaction is exothermic or endothermic. (1)
(b) Explain your answer. (1)
(c) State why a polystyrene cup is used rather than a glass beaker. (1)
Mark scheme
(a) Exothermic [1]
(b) The temperature increased, showing that heat energy was released to the surroundings [1]
(c) Polystyrene is a good thermal insulator / reduces heat loss to the surroundings, making the temperature measurement more accurate [1]
Examiner note: The polystyrene cup acts as a calorimeter, minimising heat loss. Glass conducts heat and would allow energy to escape, giving a lower temperature change. This is a standard practical setup.
Question 3 (3 marks, Core)
Give one example of each of the following:
(a) An exothermic reaction (1)
(b) An endothermic reaction (1)
(c) An everyday use of an exothermic reaction (1)
Mark scheme
(a) Any one of: combustion / neutralisation / oxidation / respiration [1]
(b) Any one of: thermal decomposition / photosynthesis / dissolving ammonium nitrate in water / the reaction of citric acid with sodium hydrogencarbonate [1]
(c) Any one of: hand warmers (using iron oxidation) / self-heating cans / burning fuels for heating/cooking [1]
Examiner note: Combustion is the safest example of an exothermic reaction. For endothermic, thermal decomposition is the most commonly tested. “Melting” and “evaporation” are endothermic processes but are physical changes, not reactions.
Question 4 (4 marks, Supplement)
A student investigates the temperature change when different metals are added to copper sulfate solution. The results are shown below.
| Metal added | Start temp (degC) | Final temp (degC) | Temperature change (degC) |
|---|---|---|---|
| Zinc | 21 | 42 | +21 |
| Iron | 21 | 29 | +8 |
| Magnesium | 21 | 58 | +37 |
(a) State which reaction is the most exothermic. Explain why. (2)
(b) Explain, in terms of reactivity, why all three reactions are exothermic. (2)
Mark scheme
(a) Magnesium gives the greatest temperature rise (+37 degC) [1], so this reaction releases the most energy / is the most exothermic [1]
(b) All three metals are more reactive than copper [1], so they displace copper from solution. Displacement reactions where a more reactive metal displaces a less reactive one are exothermic [1].
Examiner note: The greater the difference in reactivity between the added metal and copper, the more exothermic the reaction. Magnesium is the most reactive of the three, so its displacement reaction releases the most energy.
Question 5 (3 marks, Core)
A student dissolves ammonium nitrate in water. The temperature drops from 22 degC to 14 degC.
(a) Is this process exothermic or endothermic? (1)
(b) Explain your answer in terms of energy. (1)
(c) State one use of this process. (1)
Mark scheme
(a) Endothermic [1]
(b) The temperature decreased, showing that energy was absorbed from the surroundings / from the water [1]
(c) Cold packs / instant cold packs for treating sports injuries [1]
Examiner note: The dissolving process absorbs energy from the water, causing the temperature to drop. This is used in commercial cold packs where ammonium nitrate is separated from water by a barrier that is broken when needed.
Question 6 (3 marks, Supplement)
Explain why bond-breaking is endothermic and bond-forming is exothermic.
Mark scheme
- Breaking bonds requires energy to be put in / absorbed to overcome the attractive forces between atoms [1]
- Forming bonds releases energy because the atoms move to a lower energy state / energy is released when attractive forces form between atoms [1]
- In an exothermic reaction, more energy is released by forming new bonds than is absorbed by breaking old bonds [1]
Examiner note: This is a fundamental concept. Every chemical reaction involves breaking existing bonds (energy in) and forming new bonds (energy out). The overall energy change depends on the balance between the two.
Question 7 (2 marks, Core)
Classify each of the following as exothermic or endothermic:
(a) Burning natural gas in a Bunsen burner (1)
(b) Thermal decomposition of calcium carbonate (1)
Mark scheme
(a) Exothermic [1]
(b) Endothermic [1]
Examiner note: Combustion is always exothermic — it releases energy. Thermal decomposition always requires continuous heating, which means it is endothermic — it absorbs energy. The word “thermal” is a clue: heat must be continuously supplied.
What to revise if you scored below 5
If definitions were wrong, memorise: exothermic = energy OUT (temperature rises), endothermic = energy IN (temperature drops). If you struggled to give examples, learn at least two of each type. Revisit the exothermic and endothermic reactions notes.
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