A pure substance has a boiling point of 72 ∘C72\,^\circ\mathrm{C}72∘C and a melting point of 9 ∘C9\,^\circ\mathrm{C}9∘C. It is cooled from 90 ∘C90\,^\circ\mathrm{C}90∘C to 30 ∘C30\,^\circ\mathrm{C}30∘C at constant pressure without reacting. How should its particle model change?
Close mobile particles become fixed in a regular arrangement
Fixed particles become widely separated and mobile
Widely separated particles become fixed in a regular arrangement
Widely separated particles become close together but remain able to move past one another
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.