Coal and Petroleum: Types, Formation, and Uses

Coal and Petroleum in NCERT Class 8 Science

Types of Coal

Coal, a fossil fuel, is a combustible rock primarily composed of carbon and hydrocarbons. As it forms deep within the Earth, coal undergoes three main stages of transformation from vegetation:

1. Lignite (or Brown Coal): The initial stage, lignite forms when dead plant matter is compressed. It contains a high moisture content and a low carbon percentage, making it less energy-dense than other forms of coal.

2. Bituminous Coal: This is the most abundant and energy-rich type of coal. It forms from lignite through higher heat and pressure, resulting in a lower moisture content and a higher carbon percentage.

3. Anthracite: The final stage in coal's transformation, anthracite is the hardest and cleanest coal. It is composed of almost pure carbon with minimal impurities and moisture.

Petroleum Formation

Petroleum, or crude oil, is a liquid fossil fuel formed from the remains of tiny aquatic organisms and plankton. These microscopic creatures, known as zooplankton and phytoplankton, accumulated in ancient oceans around 250 to 650 million years ago.

1. As the plankton died, they sank to the ocean floor, forming a thick layer.
2. Over millions of years, heat and pressure transformed this organic material into liquid petroleum.
3. The Earth's tectonic movements forced the liquid petroleum to accumulate in underground pockets.

Petroleum Uses

Petroleum is a versatile fossil fuel with a wide range of applications:

1. Gasoline: Petroleum is refined into gasoline, the fuel used in most motor vehicles.
2. Diesel: Petroleum is also refined into diesel fuel, used in large trucks, buses, and vehicles with diesel engines.
3. Jet Fuel: Aviation uses petroleum-based jet fuel to power airplanes.
4. Heat and electricity: Petroleum is used to generate electricity and heat in households and industries.
5. Chemicals: Petroleum is the primary source of raw materials for making chemicals such as plastics, fertilizers, and medicines.

Coal Mining

Coal is extracted from the ground through two main methods:

1. Surface mining: This method involves removing coal from the ground in a process called stripping. The top layer of the Earth is removed to expose the coal seams, which are then extracted.
2. Underground mining: This method involves digging tunnels and shafts to reach the coal seams. Coal is then extracted from the tunnels and transported to the surface.

Coal Formation

Coal forms deep within the Earth, primarily in two main stages:

1. Peat: Peat originates from the decomposition of plant matter in wetlands. It accumulates slowly over thousands of years.
2. Coalification: Peat undergoes coalification, a process where heat and pressure turn it into coal. This process takes millions of years, transforming peat into lignite, bituminous coal, and finally anthracite.

Understanding the types of coal, petroleum formation, uses of petroleum, coal mining, and coal formation is essential to comprehending the role these non-renewable resources play in our energy needs and the environment.