Starter quiz
- Which property of hydrocarbons affects their viscosity?
- boiling point
- molecular size ✓
- flammability
- solubility
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- In the fractional distillation of crude oil, which fraction is collected at the bottom of the column?
- petroleum gases
- kerosene
- diesel
- heavy fuel oil
- bitumen ✓
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- Which of the following statements about alkanes are true?
- Alkanes are hydrocarbons. ✓
- Alkanes contain single bonds between carbon atoms. ✓
- Ethane is the simplest alkane.
- Alkanes contain double bonds between carbon atoms.
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- Which of the following hydrocarbons is the most flammable?
- methane ✓
- ethane
- propane
- butane
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- What is fractional distillation?
- A process to separate a mixture of solids based on their densities.
- A technique to separate a mixture of liquids based on their boiling points. ✓
- A method to combine different liquids into a single mixture.
- A process to break down large alkanes into smaller more useful molecules.
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- Why do smaller hydrocarbon molecules have lower boiling points?
- they have fewer intermolecular forces ✓
- they have more intermolecular forces
- they are more viscous
- they are more flammable
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Exit quiz
- Which of the following fractions are commonly used as fuels for cars?
- petrol ✓
- bitumen
- liquified petroleum gas
- diesel ✓
- kerosene
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- What is the name of the thermal decomposition reaction where larger alkanes are broken down into smaller alkanes and alkenes?
- 'cracking' ✓
- Which of the following is an example of a hydrocarbon that can be cracked?
- methane
- ethene
- propene
- butane ✓
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- Which process involves heating larger alkanes to vapourise them, mixing with steam and heating to high temperatures to break down the hydrocarbon molecules?
- cracking ✓
- neutralisation
- simple distillation
- fractional distillation
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- Which of the following statements about alkenes is false?
- They have a double bond between carbon atoms.
- They are unsaturated hydrocarbons.
- They react with bromine water.
- Bromine water remains an orange/brown colour when an alkene is added. ✓
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- Which statement best describes why different fractions of crude oil have different properties and uses?
- They have the same boiling points but different densities.
- They have different boiling points, viscosities, and flammabilities. ✓
- They have the same chemical structure but different colours.
- They have the same boiling point.
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Worksheet
Presentation
Video
Lesson Details
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.
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.
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.