Crude Oil
7 marks · HardCrude oil is essential to our way of life and one of its products, kerosene, is widely used.
State what crude oil is mainly composed of, and explain what hydrocarbons are.
Describe two properties of hydrocarbon molecules found in kerosene that make them suitable for use as fuel in jet engines.
Give one typical use of kerosene.
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(a) Crude oil is made of hydrocarbons, which are compounds containing only carbon and hydrogen atoms · must show mixture of hydrocarbons, definition: hydrocarbons contain only C and H
(b) Hydrocarbons in kerosene have suitable boiling points and are volatile enough to burn easily, but not so volatile as to be dangerous; they also burn with a clean flame providing lots of energy · must show suitable boiling point/volatility, burns cleanly/good energy
(c) Kerosene is used as jet fuel or as domestic heating oil · must show any correct use
Common mistakes: Saying crude oil is made of pure elements
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Marking points
A1 (a) · 1 mark · States crude oil is a mixture of hydrocarbons
A2 (a) · 1 mark · Defines hydrocarbon as a compound containing carbon and hydrogen only
A3 (a) · 1 mark · Provides an example or further details, e.g. molecules of varying size
B1 (b) · 1 mark · Mentions boiling point/volatility that suits jet fuel use
B2 (b) · 1 mark · Mentions burning properties (e.g., burns cleanly, gives lots of energy)
C1 (c) · 2 marks · Gives any single valid use of kerosene
Worked solution
a) Crude oil is mainly composed of hydrocarbons. Hydrocarbons are compounds made up of only carbon and hydrogen atoms. The mixture contains many different hydrocarbons, with molecules of different sizes.
b) The hydrocarbons in kerosene have a boiling point that allows them to vaporise and burn in jet engines. They are also volatile enough to burn easily but not so volatile as to be dangerous. When burnt, they produce much energy and leave little residue (burn cleanly).
c) A typical use of kerosene is as a fuel for jet aircraft (aviation fuel), but it is also used as heating oil in some homes.