Contents
Independent final check
Explain without the key
calculate / predict / explain
Final check
Solid hydrated barium hydroxide and solid ammonium chloride are mixed in a beaker. A thermometer pushed into the mixture reads 17.5 °C at the start and −7.0 °C at its lowest. (a) Calculate the fall in temperature. (b) The beaker stands in a small puddle of water on a wooden block. Predict what happens to the puddle. Explain your prediction using the words thermal energy and surroundings.
calculate: work out the answer from the data. predict: use the information to say what you expect. 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