A temperature probe is used inside a glass-making tank. A protective sleeve around the probe must remain solid at 1400 ∘C1400\ ^{\circ}\text{C}1400 ∘C during normal operation.
| Substance | Arrangement of particles | Melting point |
|---|---|---|
| P | Atoms joined by covalent bonds in a large continuous network | 1680 ∘C1680\ ^{\circ}\text{C}1680 ∘C |
| Q | Separate small molecules | 90 ∘C90\ ^{\circ}\text{C}90 ∘C |
In an emergency, the temperature in the tank may reach 1750 ∘C1750\ ^{\circ}\text{C}1750 ∘C.
Explain which substance should be used for the sleeve during normal operation. In your answer, explain whether this substance would remain solid in an emergency and why the melting points of P and Q are different.
122 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.