Fractional distillation of crude oil | Combined science

Starter quiz

Which elements are hydrocarbons composed of?

oxygen

hydrogen ✓

carbon ✓

sodium
Why is crude oil considered a non-renewable resource?

it is produced quickly by natural processes

it can be replaced within a human lifetime

it forms over millions of years from ancient organic matter ✓

it is an unlimited resource
What key term is used to describe the temperature at which a substance changes from a liquid state to a gas state?

'boiling point' ✓
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.
Why is complete combustion preferred over incomplete combustion?

it produces more carbon monoxide

it is less efficient

it releases more energy ✓

it requires less oxygen
Match the definition with the correct key term.

viscosity

⇔

how easily a liquid flows ✓

flammability

⇔

the ease with which a substance will ignite ✓

distillation

⇔

a separation technique that uses boiling and condensation ✓

fraction

⇔

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

alkanes

⇔

saturated hydrocarbons ✓

Exit quiz

What is crude oil primarily composed of?

pure carbon

a mixture of different hydrocarbons and impurities ✓

pure hydrocarbons

water and minerals
What is the name of the method used to separate miscible fluids (liquids or gases) with different boiling points into individual components?

'fractional distillation' ✓
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

to provide a temperature gradient ✓

to store the distilled components after separation
In fractional distillation of crude oil, which of the following fractions has the lowest boiling point?

diesel

kerosene

petroleum gases ✓

bitumen
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.

Components with lower boiling points condense at the top of the column. ✓

Components with higher boiling points are collected as gases.
Which statement about smaller hydrocarbon molecules is true?

They have higher boiling points, are less flammable and more viscous.

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.

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Lesson Details

Key learning points

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

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.

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.