COAL AND PETROLEUM | Class 8 Science Notes

Coal

Coal is a hard, black-colored natural fuel that has been used by humans for centuries. It is primarily composed of carbon and is formed from the remains of plants that lived in swampy forests about 300 million years ago. These plants died and fell into the swamp water, forming thick layers of plant debris called peat. Over time, natural processes such as flooding buried these layers under soil and sediment. As more layers accumulated, the pressure and temperature increased, compressing the plant material and gradually converting it into coal through a process called carbonisation.

Coal is an important fuel used for cooking, generating electricity in thermal power plants, and as a fuel in various industries. Historically, coal was also used in steam engines to power trains. When coal burns in the presence of air, it mainly produces carbon dioxide gas along with heat energy.

Coal is mined from underground or surface mines. The mining process involves extracting coal deposits from the earth, which are then processed to obtain useful products such as coke, coal tar, and coal gas.

Coke is a tough, porous, almost pure form of carbon obtained by heating coal in the absence of air. It is used in steel manufacturing and metal extraction.

Coal tar is a thick, black liquid with a strong smell, containing about 200 substances. It is used as a raw material in the production of synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, and roofing materials. Naphthalene balls used to repel moths are also derived from coal tar. Bitumen, a petroleum product, is now often used instead of coal tar for road surfacing.

Coal gas, produced during coke manufacturing, was historically used for street lighting and is now used as a fuel in industries near coal processing plants.

📊 Diagram: Fig. 3.1: Coal; About 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like flooding, these forests got buried under the soil. As more soil deposited over them, (See figure_2, figure_3)

🔗 Connection: Prepares the understanding for petroleum, another fossil fuel formed from ancient organisms.