very-high Explain questions (3-4 marks): Explain why fractional distillation separates fractions — must mention boiling points, condensation, and forces between molecules.
high Properties questions (2 marks): Predict properties of a fraction based on chain length — shorter = lower bp, more flammable, less viscous.
high Physical vs chemical (1 mark): Fractional distillation is physical; cracking is chemical. This distinction is frequently tested.
Common exam question: "Why is fraction X collected at a higher position than fraction Y?" — Answer: X has lower boiling point/shorter chain, so rises higher before condensing.
Edexcel 1CH0: Examined in Paper 2 (1CH0/2). Edexcel tests fractional distillation, uses of fractions, and the trend in boiling point — common 4-mark questions on Paper 2. In Edexcel-style questions, the command word "Suggest" appears frequently — use your chemistry knowledge to apply to an unfamiliar context.
This exam focus covers Exam Focus: Crude Oil within Crude Oil for GCSE Chemistry. Topic 37: Crude Oil It is section 11 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Crude Oil
A hydrocarbon is a compound that contains only:
Explain how fractional distillation separates crude oil into different fractions.