A student measures the temperature change when magnesium ribbon reacts with dilute hydrochloric acid in an open polystyrene cup.
State why adding a lid to the polystyrene cup would help to give a more accurate value for the temperature change.
94 exam-style questions on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. Each one has a worked solution and a mark scheme showing where the marks go.