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This question is about crude oil and alkanes - AQA - GCSE Chemistry Combined Science - Question 5 - 2020 - Paper 2
Question 5
This question is about crude oil and alkanes. 05.1 Describe how crude oil is formed. 05.2 Describe how crude oil is separated into fractions by fractional distilla... show full transcript
Worked Solution & Example Answer:This question is about crude oil and alkanes - AQA - GCSE Chemistry Combined Science - Question 5 - 2020 - Paper 2
Step 1
Describe how crude oil is formed.
Answer
Crude oil is formed from the remains of plankton, which are marine organisms. These remains become buried in mud and are subjected to high temperature and pressure over millions of years. This process transforms the organic material into hydrocarbons, which make up crude oil.
Step 2
Describe how crude oil is separated into fractions by fractional distillation.
Answer
In fractional distillation, crude oil is heated to vaporize it. The vapor then rises through a fractionating column where it cools. Different fractions collect at different levels based on their boiling points. Lighter fractions with lower boiling points exit the column first, while heavier fractions with higher boiling points condense and are collected at lower levels.
Step 3
Step 4
Explain the trend in the boiling points of the alkanes.
Answer
The boiling point of the alkanes increases as the number of carbon atoms increases. This is due to the fact that larger molecules have greater intermolecular forces, specifically van der Waals forces, which require more energy to overcome. Therefore, as the size of the molecules increases, so does the boiling point.
Step 5