Crude Oil
7 marks · HardCrude oil is an important natural resource formed over millions of years and separated into different fractions for various uses, including kerosene.
Describe the process by which crude oil forms from ancient sea plants and animals over millions of years. Include two different physical factors essential to this process.
State what kerosene is used for. Give two different uses.
Explain why kerosene, as a fraction of crude oil, is useful for these applications, referring to its physical properties.
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(a) — · must show Reference to ancient sea plants and animals dying and being buried, Sedimentation or sediment layers, Application of heat, Application of high pressure, Transformation over millions of years to crude oil, Recognition it is a slow process/natural process (not synthetic)
(b) — · must show Fuel for jet aircraft, Domestic heating oil, Paraffin for lamps/heaters, Any two correct uses accepted
(c) — · must show Boiling point suitable for fuel use, Flows easily (less viscous than heavier fractions), Produces energy efficiently on burning, Volatility suitable for engines/heaters, Any two correct linked to use
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Marking points
M1 (a) · 1 mark · References death and burial of ancient sea plants and animals.
M2 (a) · 1 mark · Mentions sedimentation and layers covering remains.
M3 (a) · 1 mark · States heat and/or high pressure turns remains into crude oil over millions of years.
B1 (b) · 1 mark · States any one correct use of kerosene (e.g., jet fuel, heating oil, lamp fuel).
B2 (b) · 1 mark · States a second correct use of kerosene.
M4 (c) · 1 mark · Links physical property of kerosene (e.g., suitable boiling point, flows easily, burns well, suitable volatility) to its use.
A1 (c) · 1 mark · Correctly explains why that property suits the application.
Worked solution
a. Over millions of years, ancient sea plants and animals died and their remains settled on the sea floor. Layers of sediment gradually covered these remains. With the passage of time, heat from the Earth and high pressure from the overlying sediments transformed the soft tissues into crude oil through chemical changes. This process took millions of years and could not be reproduced artificially in a short period.
b. Kerosene is used as a fuel for jet aircraft and as domestic heating oil. It is also used as 'paraffin' for small heaters and lamps.
c. Kerosene is useful for these applications because it has a boiling point that allows it to remain as a liquid at normal temperatures, but it vaporises easily enough to burn efficiently in engines and heaters. It is less viscous than heavier oil fractions, which helps it flow easily through pipes and fuel systems.