Cracking fractions of crude oil
Lesson details
Learning outcome
I can describe the uses of different fractions of crude oil and describe what cracking is and how it is used to produce lighter fractions that are in greater demand.
Key learning points
- Fractions of crude oil have different properties and uses, affecting the demand for these molecules.
- Larger hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules.
- Cracking can be done by various methods including catalytic cracking and steam cracking.
- The products of cracking include alkanes and alkenes, which have a double bond between two carbon atoms.
- Bromine water changes from orange/brown to colourless in the presence of an alkene.
Keywords
Cracking - Cracking is a thermal decomposition reaction where larger alkanes are broken down into smaller alkanes and alkenes.
Thermal decomposition - A thermal decomposition reaction is a type of reaction that uses heat to break down a reactant compound into two or more products.
Catalyst - A catalyst is a chemical that speeds up the rate of a reaction without itself being used up.
Saturated - Alkanes are saturated hydrocarbons as they contain only single bonds between carbon atoms.
Unsaturated - Unsaturated compounds contain at least one carbon-carbon double covalent bond.
Common misconception
Cracking is the same as fractional distillation.
Fractional distillation separates hydrocarbons based on their boiling points. Cracking alters the molecular formula of compounds.
Teacher tip
A teacher demonstration showing the cracking of paraffin could be performed.
Licence
except where otherwise stated. See Oak's terms & conditions (Collection 2).Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which property of hydrocarbons affects their viscosity?
Q2.In the fractional distillation of crude oil, which fraction is collected at the bottom of the column?
Q3.Which of the following statements about alkanes are true?
Q4.Which of the following hydrocarbons is the most flammable?
Q5.What is fractional distillation?
Q6.Why do smaller hydrocarbon molecules have lower boiling points?
Assessment exit quiz
6 Questions
Q1.Which of the following fractions are commonly used as fuels for cars?
Q2.What is the name of the thermal decomposition reaction where larger alkanes are broken down into smaller alkanes and alkenes?
Q3.Which of the following is an example of a hydrocarbon that can be cracked?
Q4.Which process involves heating larger alkanes to vapourise them, mixing with steam and heating to high temperatures to break down the hydrocarbon molecules?
Q5.Which of the following statements about alkenes is false?
Q6.Which statement best describes why different fractions of crude oil have different properties and uses?
To help you plan your 11 combined science lesson on: Cracking fractions of crude oil, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 11 combined science lesson on: Cracking fractions of crude oil, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
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The assessment exit quiz will test your pupils' understanding of the key learning points.
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