Alkanes are a family of compounds of carbon and hydrogen.
The table shows information about some alkanes.
| Number of carbon atoms | Formula | Melting point (°C) | Boiling point (°C) |
|---|---|---|---|
| 1 | CH₄ | −182 | −162 |
| 3 | C₃H₈ | −188 | −42 |
| 5 | C₅H₁₂ | −130 | 36 |
| 7 | C₇H₁₆ | −91 | 98 |
| 9 | C₉H₂₀ | −54 | 151 |
Deduce the formula of the alkane with 20 carbon atoms.
Predict the state of C₃H₈ and the state of C₉H₂₀ at −50 °C.
Describe and explain the trend in the boiling points of the alkanes.
Poly(ethene) is a polymer. Its molecules are chains of thousands of carbon atoms. It is made from ethene, which has two carbon atoms per molecule and is a gas at room temperature.
A student says:
"Poly(ethene) should be a gas or a liquid at room temperature, because it is made from ethene, which is a gas."
Evaluate the student's statement.
A sample of poly(ethene) softens over a range of temperatures rather than melting at one temperature.
Suggest why.
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.