A student investigated the temperature changes that occur when different salt samples are dissolved in water.
Their results are shown in the table below.
| Salt | Starting temperature of water in °C | Temperature of mixture after 3 minutes in °C | Temperature change in °C |
|---|---|---|---|
| P | 18.5 | 12.1 | -6.4 |
| Q | 18.5 | 24.2 | +5.7 |
| R | 18.5 | 11.2 |
Calculate the temperature change for salt R.
Include a sign/symbol in your answer to show if the temperature change is an increase (+) or a decrease (-).
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.