Ch 5 covers fossil fuels — coal, petroleum, and natural gas. Students learn how they formed, the products of petroleum refining, and why conservation is crucial since they are exhaustible.
Coal: formed over millions of years from buried dead forests under high temperature and pressure (carbonisation). Found in underground mines. Petroleum: formed from dead marine organisms buried under the sea floor. Extracted by drilling oil wells. Takes millions of years — hence non-renewable.
Petroleum refining gives: LPG, petrol, diesel, kerosene, paraffin wax, lubricating oil, bitumen. Natural gas (mainly methane): cleanest fossil fuel, used as CNG for vehicles. Conservation: use public transport, switch off electricity, use renewable energy sources (solar, wind, hydro).
Download: https://ncert.nic.in/textbook/pdf/hesc105.pdf | Complete book: https://ncert.nic.in/textbook/pdf/hesc1ps.zip
Fossil fuels took millions of years to form from dead organisms under specific conditions. We are consuming them much faster than they can be replaced. Once exhausted, they cannot be regenerated in our lifetime — hence non-renewable.
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