Ice at −20 ∘C-20\,^\circ\mathrm{C}−20∘C is heated steadily until it becomes steam at 120 ∘C120\,^\circ\mathrm{C}120∘C.
The temperature stays constant for much longer at 100 ∘C100\,^\circ\mathrm{C}100∘C than at 0 ∘C0\,^\circ\mathrm{C}0∘C.
Which statement explains this?
Boiling is a chemical change, so it needs more energy than melting.
The particles in steam are bigger than the particles in water, so more energy is needed to make them.
More energy is needed to separate the particles completely during boiling than to let them move past one another during melting.
Boiling happens at a higher temperature, so the particles stop moving for longer.
48 exam-style questions on OCR GCSE Chemistry 1.1 The particle model, covering 1.1.1 The particle model and changes of state and 1.1.2 Limitations of the particle model. Each one has a worked solution and a mark scheme showing where the marks go.