The table shows the melting points and boiling points of five substances.
| Substance | Melting point (°C) | Boiling point (°C) |
|---|---|---|
| bromine | −7 | 59 |
| chlorine | −101 | −34 |
| ethanol | −114 | 78 |
| iron | 1538 | 2862 |
| sodium chloride | 801 | 1413 |
Which substance is a gas at 25 °C?
What is the state of bromine at 70 °C?
Which two substances are liquids at 0 °C?
Explain why chlorine has a much lower boiling point than sodium chloride.
Use ideas about forces and energy.
A student says:
"When chlorine boils, the covalent bonds between the chlorine atoms break."
Is the student correct? Explain your answer.
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.