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Year 11
AQA
Higher

Fractional distillation of crude oil

I can describe how crude oil can be separated into fractions using fractional distillation, and describe the differences in properties between fractions.

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Year 11
AQA
Higher

Fractional distillation of crude oil

I can describe how crude oil can be separated into fractions using fractional distillation, and describe the differences in properties between fractions.

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Lesson details

Key learning points

  1. Crude oil is a non-renewable mixture of different hydrocarbons and impurities.
  2. Crude oil can be separated into groups of hydrocarbon molecules of similar size, called fractions.
  3. Most of the hydrocarbon molecules in crude oil are alkanes.
  4. Smaller hydrocarbon molecules have lower boiling points, are more flammable, and are less viscous.
  5. Fractions of crude oil include petroleum gases, petrol, kerosene, diesel oil, heavy fuel oil, and bitumen.

Keywords

  • Crude oil - Crude oil is a fossil fuel formed over millions of years from dead plankton. It is a mixture of different hydrocarbons and impurities.

  • Hydrocarbon - Hydrocarbons are covalent compounds containing hydrogen and carbon atoms only.

  • Viscosity - Viscosity is how easily a liquid flows. The higher the viscosity, the less easily a liquid flows.

  • Fractional distillation - Fractional distillation is a method used to separate miscible fluids (liquids or gases) with different boiling points into individual components (fractions).

  • Fraction - A fraction is a part of a mixture that has been separated by fractional distillation.

Common misconception

Some students may think that fractional distillation produces new substances from crude oil.

It is important to emphasise that crude oil is a mixture, and the process of fractional distillation is to separate out the different hydrocarbons based on their boiling points.

Students could perform a class practical of fractional distillation using a crude oil substitute. They can collect different fractions and test them for viscosity and flammability. It is essential to complete your own risk assessment for this practical.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which elements are hydrocarbons composed of?
oxygen
Correct answer: hydrogen
Correct answer: carbon
sodium
Q2.
Why is crude oil considered a non-renewable resource?
it is produced quickly by natural processes
it can be replaced within a human lifetime
Correct answer: it forms over millions of years from ancient organic matter
it is an unlimited resource
Q3.
What key term is used to describe the temperature at which a substance changes from a liquid state to a gas state?
Correct Answer: boiling point, boiling
Q4.
Order these statements to explain how crude oil is formed.
1 - Dead plankton settled at the bottom of the oceans.
2 - The dead plankton was covered in mud and other sediments.
3 - The buried organic matter is subjected to high temperatures and pressures.
4 - Continued heat and pressure breaks downs the organic matter into crude oil.
Q5.
Why is complete combustion preferred over incomplete combustion?
it produces more carbon monoxide
it is less efficient
Correct answer: it releases more energy
it requires less oxygen
Q6.
Match the definition with the correct key term.
Correct Answer:viscosity,how easily a liquid flows

how easily a liquid flows

Correct Answer:flammability,the ease with which a substance will ignite

the ease with which a substance will ignite

Correct Answer:distillation,a separation technique that uses boiling and condensation

a separation technique that uses boiling and condensation

Correct Answer:fraction,a part of a mixture that has been separated by fractional distillation

a part of a mixture that has been separated by fractional distillation

Correct Answer:alkanes,saturated hydrocarbons

saturated hydrocarbons

Exit quiz

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6 Questions

Q1.
What is crude oil primarily composed of?
pure carbon
Correct answer: a mixture of different hydrocarbons and impurities
pure hydrocarbons
water and minerals
Q2.
What is the name of the method used to separate miscible fluids (liquids or gases) with different boiling points into individual components?
Correct Answer: fractional distillation
Q3.
What is the purpose of the fractionating column in fractional distillation?
to heat crude oil until it all vapourises
to cool the crude oil quickly
Correct answer: to provide a temperature gradient
to store the distilled components after separation
Q4.
In fractional distillation of crude oil, which of the following fractions has the lowest boiling point?
diesel
kerosene
Correct answer: petroleum gases
bitumen
Q5.
Which of the following statement about the separation of components in fractional distillation is true?
Components with higher boiling points condense at the top of the column.
Components with lower boiling points condense at the bottom of the column.
Correct answer: Components with lower boiling points condense at the top of the column.
Components with higher boiling points are collected as gases.
Q6.
Which statement about smaller hydrocarbon molecules is true?
They have higher boiling points, are less flammable and more viscous.
Correct answer: They have lower boiling points, are more flammable and less viscous.
They have higher boiling points, are more flammable, and more viscous.
They have lower boiling points, are less flammable, and more viscous.