The origin of crude oil
2 marks · NormalGive two differences between small and large hydrocarbon molecules found in crude oil.
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.
Show answer
Small hydrocarbons have lower boiling points and are more volatile; large hydrocarbons have higher boiling points and are less volatile (more viscous, flow less easily, darker, burn less easily).
Also accept: Small: runnier, lighter colour, burn more easily. Large: more viscous, darker, burn less easily.
Common mistakes: Mixing up properties
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States a difference in boiling point or volatility or viscosity.
B2 · 1 mark · Describes a second property or difference (such as colour, ease of burning, flow).
Worked solution
Small hydrocarbons have lower boiling points and are more volatile. Large hydrocarbons have higher boiling points and are less volatile.