As fuels

2 marks · Hard

State two reasons why the fractions obtained from crude oil by fractional distillation are useful as fuels.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

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Also accept: They burn readily to release energy / heat.; Different fractions have boiling points suited to different uses.; They can be used in vehicles/heating because they easily vaporise and combust.; They are plentiful and convenient to use as energy sources.

Common mistakes: Stating that they are all liquids/gases (not universally true).; Giving non-reasons such as 'they come from crude oil.'

Show mark scheme and worked solution

Marking points

B1 · 1 mark · States any reason why a fraction is suitable as a fuel (e.g. releases energy on burning; combusts easily; can be used in engines/heating).

B2 · 1 mark · Gives a second distinct reason related to properties or uses as a fuel (e.g. specific boiling points allow different applications; produce large amounts of heat).

Worked solution

1. The fractions burn to produce a lot of heat energy, which is useful for engines and heating (B1).

2. The different boiling points mean fractions can be chosen for specific uses, such as petrol for cars or kerosene for aircraft (B2).