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Fossil Fuels: Sunlight Stored Underground
Coal, petroleum and natural gas are called fossil fuels because they formed from the remains of plants and tiny sea organisms buried millions of years ago. Heat from the Earth and heavy pressure slowly converted that buried matter into carbon-rich fuels. They are non-renewable: we burn them in decades, but they need millions of years to form. Burning them releases carbon dioxide, and coal and diesel also release sulphur dioxide and soot, which is why they dominate air-pollution questions. Yet they supply most of the world's energy, run transport and give raw material for plastics, fertilisers and medicines. Exams ask the stages of coal, the order of petroleum fractions, what LPG and CNG contain and what 'octane number' means. All four are covered in these cards.
1. Which type of coal has the highest carbon content?
2. Strongly heating coal in the absence of air is known as:
3. Which of these petroleum fractions is collected at the top of the fractionating column?
4. The main constituent of CNG is:
5. LPG used in domestic cylinders is mainly a mixture of:
6. Which chemical is added to LPG so that a gas leak can be detected by smell?
7. A petrol with octane number 87 behaves like a mixture of:
8. Which is the correct order of petroleum fractions from the top of the column to the bottom?