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- Recall coal, natural gas and petroleum as fossil fuels that produce carbon dioxide on combustion.
Coal, natural gas and petroleum all contain carbon, so when it burns, the carbon reacts with oxygen in the air to produce carbon dioxide.
- Name methane as the main constituent of natural gas.
Natural gas is a mixture of a lot of gases, but the main constituent is methane.
- Describe petroleum as a mixture of hydrocarbons and its separation into useful fractions by fractional distillation.
Petroleum extracted in an oil refinery are separated into different fractions (groups with a limited range of carbon atoms) by fractional distillation. Each fraction has a different boiling point and so they can be evaporated using heat in a fractional distillation column and separated from each other. Here are the different fractions (and their uses) separated in the petroleum distillaltion.
- Understand the essential principle of fractional distillation in terms of differing boiling points (ranges) of fractions related to molecular size and intermolecular attractive forces.
Different molecular sizes and intermolecular attractive forces between the elements cause them to boil off at different fractions. Fractions with larger molecules will have higher boiling points (because it’s harder to boil and evaporate when the molecules are bigger). The large molecules also mean that their intermolecular forces are stronger, making them very hard to break apart and keep the substance thick.
As you can see from the labeled diagram above, as you go up the column, the molecules get smaller and the substance gets more runny.
- State the use of:
• refinery gas for bottled gas for heating and cooking
• gasoline fraction for fuel (petrol) in cars
• diesel oil / gas oil for fuel in diesel engines.
Looks like the syllabus itself explained it 😀
Notes submitted by Lintha
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