The graph below shows a curve obtained when water at 20℃ was heated for 15 mins.
![graph showing a curve when water is heated](https://www.easyelimu.com/images/form_3_past_papers/Term_1_2021/graph_showing_a_curve_when_water_is_heated.JPG)
- What happens to the water molecules between points W and X
- In which part of the curve does a change of state occur?
- Explain why the temperature does not rise between points X and Y