In an investigation into temperature changes, the reaction is carried out in a polystyrene cup with a lid rather than in an open glass beaker. Why is this done?
The lid stops the reaction mixture evaporating while it is being stirred
Polystyrene reacts with the mixture and releases its energy more slowly
Less energy is transferred to the surroundings, so the measured temperature change is larger
The cup and lid make the reaction happen faster, so the reading is taken sooner
39 exam-style questions on AQA GCSE Chemistry 5.1 Exothermic and endothermic reactions, covering 5.1.1 Energy transfer during exothermic and endothermic reactions, 5.1.2 Reaction profiles, and 5.1.3 The energy change of reactions. Each one has a worked solution and a mark scheme showing where the marks go.