Crude Oil
6 marks · NormalCrude oil is separated into different fractions in an oil refinery. Some of these fractions are used as fuels in daily life.
Describe briefly how crude oil is separated into fractions in a refinery.
Name two main fractions obtained from fractional distillation and state one typical use for each.
Refinery gases are an important by-product at a refinery. State one use of refinery gases.
Give the main use of gasoline in modern society.
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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(a) Crude oil is heated until it boils; the vapours pass up a fractionating column, condensing at different heights according to their boiling points. · must show crude oil heated/boiled, vapours/fractions separated by boiling point in a column
(b) e.g., Refinery gases (used as LPG for heating/cooking); Gasoline (used as car fuel). · must show names of two main fractions, one correct use for each
(c) Used as LPG for domestic heating/cooking (or similar suitable use from content). · must show use of refinery gases
(d) Used as a fuel in cars. · must show car fuel
Common mistakes: Listing products that are not main fractions; Giving incorrect uses for the stated fraction
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States that crude oil is heated/boiled and the vapours are separated.
A1 (a) · 1 mark · Mentions condensation at different heights depending on boiling point in the fractionating column.
B1 (b) · 1 mark · Names two main fractions correctly (e.g., refinery gases, gasoline, kerosene, diesel oil, fuel oil, bitumen).
B2 (b) · 1 mark · Gives a typical correct use for both fractions.
B3 (c) · 1 mark · States one valid use of refinery gases (e.g., LPG for heating/cooking).
B4 (d) · 1 mark · States main use of gasoline (fuel for cars).
Worked solution
a) Crude oil is first heated until it boils. The vapours rise into a fractionating column. As the vapours cool while passing up the column, they condense at different heights depending on their boiling points.
b) Two main fractions are refinery gases and gasoline. Refinery gases are used as LPG for cooking or heating, while gasoline is used as a fuel in cars.
c) Refinery gases are used as LPG for domestic heating and cooking.
d) Gasoline is mainly used as a fuel for cars.