Contents
Return after a break
What can you recall?
explain
Recall and explain
Each pupil's statement is incorrect. (a) Plaster of Paris mixed with water gets warm as it sets. Pupil 1 writes: "The plaster feels warm because the reaction takes in thermal energy from my hand." Explain why the statement is incorrect. (b) Two solutions are mixed in a polystyrene cup, and the thermometer falls from 23.5 °C to 18.0 °C. Pupil 2 writes: "The reacting chemicals lost thermal energy, so the reaction is endothermic." Explain why the statement is incorrect.
explain: give reasons and connect them to evidence.
Your saved work
Answers, earlier attempts and your Pause and check notes stay in this browser. Export a copy to keep, to move to another device or to hand to your teacher. Importing a copy keeps your current answers and adds earlier attempts.
Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
Energy changes in reactions (5.1 Core 1–3, Supplement 4–6): exothermic and endothermic reactions and the temperature of the surroundings, reaction pathway diagrams, the enthalpy change ΔH and its sign, activation energy, and drawing and labelling pathway diagrams. Bond breaking, bond making and bond energies are in the next module; collisions and catalysts in topic 6.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus