The table shows the melting points and boiling points of four substances, P, Q, R and S.
| Substance | Melting point (∘C^\circ\mathrm{C}∘C) | Boiling point (∘C^\circ\mathrm{C}∘C) |
|---|---|---|
| P | −95 | 69 |
| Q | −30 | 35 |
| R | −7 | 59 |
| S | −114 | −34 |
A sample of each substance is warmed from −50 ∘C-50\,^\circ\mathrm{C}−50∘C to 50 ∘C50\,^\circ\mathrm{C}50∘C.
Which substance changes state twice?
P
Q
R
S
60 exam-style questions on OCR GCSE Chemistry 2.3 Properties of materials, covering 2.3.1 Carbon bonding and the variety of organic compounds, 2.3.2 Diamond, graphite, fullerenes and graphene, 2.3.3 Bond strength, changes of state and predicting states, 2.3.4 Bulk properties and types of bonding, and 2.3.5 Nanoparticles: scale, surface area, uses and risks. Each one has a worked solution and a mark scheme showing where the marks go.