What are Coal and Petroleum? Formation, Types and Uses Explained
Coal and petroleum are the most significant non-renewable energy sources that have shaped modern civilization. These organic fossil fuels, formed through the geological transformation of ancient plant and animal remains over millions of years, serve as primary energy sources for electricity generation, transportation, and industrial processes. Understanding their formation, properties, and applications is fundamental for students studying conventional sources of energy in physics and chemistry.
What Are Coal and Petroleum?
Coal and petroleum belong to the category of fossil fuels, which are naturally occurring hydrocarbon deposits derived from organic matter that underwent transformation under specific geological conditions. These resources took millions of years to form and are considered non-renewable because their rate of consumption far exceeds their natural formation rate.
Coal is a solid, black or brownish-black sedimentary rock composed primarily of carbon, hydrogen, oxygen, nitrogen, and sulfur. It forms when plant material accumulates in swampy environments and gets buried under layers of sediment. Over geological time scales, heat and pressure convert this organic matter into coal through a process called coalification.
Petroleum, also known as crude oil, is a liquid mixture of hydrocarbons found beneath the Earth's surface. It originates from the remains of ancient marine organisms like plankton and algae that settled on ocean floors millions of years ago. Through diagenesis and catagenesis processes, these organic materials transform into petroleum under specific temperature and pressure conditions.
Formation Process of Coal and Petroleum
The formation of coal occurs through a multi-stage process that begins in oxygen-poor environments like swamps and marshes. Dead plant material accumulates and forms peat, which is the first stage of coal formation. As more sediments deposit over the peat, increasing pressure and temperature gradually transform it into different types of coal.
- Peat: The initial stage with 60% carbon content
- Lignite: Brown coal with 60-70% carbon content
- Bituminous coal: Soft coal with 70-85% carbon content
- Anthracite: Hard coal with 85-95% carbon content
Petroleum formation follows a different pathway. Marine microorganisms settle in sedimentary layers on ocean floors, where anaerobic conditions prevent complete decomposition. Over millions of years, burial under sedimentary layers subjects this organic matter to increasing temperature and pressure, converting it into kerogen and eventually into petroleum hydrocarbons.
Physical and Chemical Properties
Coal exhibits varying physical properties depending on its type and carbon content. Its density ranges from 1.1 to 1.5 g/cm³, while its calorific value increases with carbon percentage. The moisture content decreases as coal matures from lignite to anthracite, affecting its burning characteristics and thermal properties.
| Coal Type | Carbon Content (%) | Calorific Value (MJ/kg) | Moisture Content (%) |
|---|---|---|---|
| Peat | 55-60 | 15-20 | 75-85 |
| Lignite | 60-70 | 20-25 | 35-75 |
| Bituminous | 70-85 | 25-35 | 2-15 |
| Anthracite | 85-95 | 32-40 | 2-8 |
Petroleum consists of various hydrocarbon compounds with different molecular weights and structures. Its density typically ranges from 0.8 to 0.95 g/cm³, making it lighter than water. The viscosity varies significantly depending on the molecular composition and temperature conditions.
Uses of Coal and Petroleum
Coal serves multiple purposes in modern society, with electricity generation being its primary application. Coal-fired power plants burn coal to produce steam that drives turbines connected to generators, converting chemical energy into electrical energy. This process involves the combustion reaction:
Industrial applications of coal include steel production, cement manufacturing, and chemical synthesis. Coking coal, a specific type of bituminous coal, is essential for steel production as it provides the carbon necessary for converting iron ore into steel in blast furnaces.
- Electricity generation in thermal power plants
- Steel and iron production
- Cement manufacturing
- Paper and aluminum industries
- Production of activated carbon and coal tar
Petroleum products dominate the transportation sector, providing fuel for automobiles, aircraft, ships, and trains. Through refining processes, petroleum yields various products including gasoline, diesel, kerosene, lubricating oils, and petrochemicals used in plastic production.
Environmental Impact and Conservation
The combustion of coal and petroleum releases significant quantities of carbon dioxide and other pollutants into the atmosphere, contributing to climate change and air pollution. Coal burning produces sulfur dioxide, nitrogen oxides, and particulate matter, while petroleum combustion generates carbon monoxide, hydrocarbons, and nitrogen compounds.
FAQs on Coal and Petroleum: Complete Class 8 Study Guide with Notes and Practice Questions
1. What are coal and petroleum?
Coal and petroleum are natural resources known as fossil fuels used for energy production.
Key points:
- Coal is a black, solid fossil fuel mainly used for electricity generation and in industries.
- Petroleum is a liquid fossil fuel found underground that is refined for products like petrol, diesel, kerosene, and lubricants.
- Both are formed from the remains of dead plants and animals buried for millions of years.
2. How is coal formed?
Coal forms from the remains of vegetation that lived millions of years ago and got buried under soil and sediment.
The process includes:
- Plants and trees in swampy areas died, fell, and accumulated over time.
- The remains were buried under clay, sand, and other materials.
- High pressure and temperature converted these remains into peat, then into lignite, bituminous coal, and finally anthracite.
3. What are the main uses of petroleum?
Petroleum is mainly used as a source of energy and raw materials for various products.
Major uses:
- Fuel for vehicles: Petrol, diesel, and LPG.
- Making kerosene, lubricants, and grease.
- Source for chemicals like plastic, synthetic fibres, and medicines.
4. What is the difference between coal and petroleum?
Coal and petroleum are both fossil fuels, but they differ in formation, state, and uses.
Differences include:
- Coal – solid, formed mainly from plants; used in power plants and as fuel.
- Petroleum – liquid, formed from marine animals and plants; refined for fuels like petrol and diesel.
5. What are fossil fuels? Give examples.
Fossil fuels are natural energy resources formed from the remains of ancient living organisms buried under earth for millions of years.
Examples:
- Coal
- Petroleum
- Natural gas
6. Why are coal and petroleum called non-renewable resources?
Coal and petroleum are non-renewable resources because they take millions of years to form and can get exhausted if overused.
Key points:
- They cannot be replaced quickly by natural processes.
- Excessive use depletes the existing reserves.
7. How can we conserve coal and petroleum?
Conservation of coal and petroleum is essential to avoid wastage and ensure their availability for the future.
Methods to conserve:
- Use public transport and carpooling to reduce fuel consumption.
- Switch off electrical appliances when not in use.
- Promote alternative sources like solar and wind energy.
- Use energy-efficient devices.
8. What are the products obtained from coal?
Coal is processed to produce various useful products.
Main products include:
- Coke – used in steel industries.
- Coal tar – used in making synthetic dyes, drugs, and explosives.
- Coal gas – used as a fuel.
9. What is petroleum refining?
Petroleum refining is the process of separating crude petroleum into useful products.
Procedure:
- Crude oil is heated in a refinery using fractional distillation.
- It separates into products such as petrol, diesel, kerosene, lubricants, and LPG.
10. Why should we use fossil fuels judiciously?
Fossil fuels must be used judiciously because they are limited and essential for future generations.
Reasons:
- Once exhausted, they cannot be replaced quickly.
- Their overuse causes environmental problems like air pollution and global warming.
- Responsible usage ensures sustainable development.
11. What are the advantages and disadvantages of using coal and petroleum?
Coal and petroleum offer key benefits but have drawbacks.
Advantages:
- Reliable sources of energy.
- Support industry and transportation.
- Non-renewable – can be exhausted.
- Cause pollution and global warming.
- Mining and drilling damage the environment.
12. What is meant by destructive distillation of coal?
Destructive distillation of coal is heating coal in the absence of air to get useful products.
This process produces:
- Coke
- Coal tar
- Coal gas
13. What are some alternatives to fossil fuels?
Alternatives to fossil fuels include renewable energy sources that are sustainable and eco-friendly.
Examples:
- Solar energy
- Wind energy
- Hydro power
- Biogas
