What is Coal and Petroleum Class 8: Complete Science Guide

Definition and Formation of Coal and Petroleum

Coal and petroleum are natural fossil fuels formed from the remains of ancient plants and animals buried underground millions of years ago. Over time, heat and pressure transformed these remains into coal and petroleum.

• Coal forms mainly from dead plants in swampy forests.
• Petroleum forms from tiny sea plants and animals called plankton.

This process takes millions of years, making both coal and petroleum non-renewable resources. Understanding their formation helps students grasp why these fuels are limited and valuable.

Types and Composition of Coal

Coal is a black or brownish-black sedimentary rock rich in carbon. It is classified based on carbon content and energy value:

Higher carbon content means better fuel quality. Bituminous coal is most commonly used in India for power generation.

Petroleum: Composition and Uses

Petroleum, also called crude oil, is a thick, dark liquid made up of hydrocarbons—compounds of hydrogen and carbon atoms. It is extracted from underground reservoirs using oil wells.

Main uses of petroleum:

• Fuel: petrol, diesel, kerosene, LPG
• Lubricants: oils for machines
• Raw materials: plastics, synthetic fabrics, medicines

Petroleum is refined in refineries where it is separated into different useful products by a process called fractional distillation.

Comparison Between Coal and Petroleum

Here is a simple comparison table to understand coal and petroleum better:

Both are vital but have different physical forms and uses.

Environmental Impact and Conservation

Coal and petroleum are non-renewable and their extraction affects the environment:

• Mining coal causes deforestation and soil erosion.
• Burning coal and petroleum releases greenhouse gases causing air pollution and climate change.
• Oil spills harm marine life.

Conservation methods include:

• Using renewable energy sources
• Improving fuel efficiency
• Recycling petroleum products
• Reducing wastage

Students should learn these impacts to promote sustainable use.

Worked Example: Calculating Energy from Coal

If 1 kg of bituminous coal releases 24 MJ (megajoules) of energy, how much energy will 5 kg produce?

Solution:

Energy released = Energy per kg × mass

$$E = 24 \, \text{MJ/kg} \times 5 \ \text{kg} = 120 \ \text{MJ}$$

So, 5 kg of coal will release 120 MJ of energy when burned.