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Crude oil and fractional distillation
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Crude oil is a mixture of hydrocarbons. Fractional distillation separates it into useful fuels.
Crude oil
A finite resource formed over millions of years from the remains of plankton.
It is a mixture of hydrocarbons: compounds of hydrogen and carbon only. Most are alkanes, C_nH2n+2.
It is a mixture of hydrocarbons: compounds of hydrogen and carbon only. Most are alkanes, C_nH2n+2.
Fractional distillation
Crude oil is heated and its vapour rises up a column that is hot at the bottom and cool at the top.
Each fraction condenses at its own boiling point.
Top to bottom: gases, petrol, kerosene, diesel, fuel oil, bitumen.
Each fraction condenses at its own boiling point.
Top to bottom: gases, petrol, kerosene, diesel, fuel oil, bitumen.
Trends
Larger molecules have higher boiling points, are more viscous (thicker), and are harder to ignite.
Which fraction is collected at the bottom of the column, and why?
- The bottom is the hottest part.
- Only fractions with very high boiling points condense there.
- These have the largest molecules.
Answer: Bitumen: largest molecules, highest boiling point.
Crude oil is a finite mixture of hydrocarbons, separated by fractional distillation. Bigger molecules: higher boiling point, more viscous, harder to ignite, collected lower down.
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