Cambridge Secondary (7-9). Stage 8. MCE Science. Workbook - Unit 7: Exothermic and Endothermic Changes - Question 51

Jacob poured 200 cm³ of water into a beaker and measured its temperature. He added 5 g of solid potassium hydroxide to the water. He measured the temperature of the solution and recorded his results: initial temperature 22 °C, final temperature 37 °C. Tick (✓) the correct explanation.

- Water reacts with the potassium hydroxide.
- The potassium hydroxide particles break down and form new substances.
- The parts of the potassium hydroxide particles separate but no new substances form.