All things present in nature that are useful to humans are called Natural Resources. Some resources are available in unlimited quantities; others are finite and can be exhausted. Coal, Petroleum, and Natural Gas are precious natural resources called Fossil Fuels — they power our entire modern civilisation.

🌍 Types of Natural Resources

🔎 2.1 What is Coal?

• 🖤  Coal is a hard, black, combustible mineral found beneath the Earth’s surface.
• 🖤  It is the most abundant fossil fuel found in India.
• 🖤  Coal was formed from the remains of trees and plants that lived hundreds of millions of years ago.
• 🖤  Coal is a major source of energy for electricity generation in India.

🌿 2.2 Formation of Coal — Carbonisation

• 🟢  About 300 million years ago, dense forests existed in low-lying wetland areas.
• 🟢  These forests were submerged under water due to natural calamities (earthquakes, floods).
• 🟢  Plant material was covered by layers of sediment (soil, mud, rock).
• 🟢  Over millions of years, high heat and pressure converted organic matter into coal.
• 🟢  Coal is a carbon-rich substance — hence the process is called Carbonisation.

📊 2.3 Types of Coal — Quality Grades

🏭 2.4 Products Obtained from Coal (Destructive Distillation)

🗺️ 2.5 Major Coalfields in India

• 🟣  Jharia, Jharkhand — Largest and most important coalfield in India
• 🟣  Raniganj, West Bengal — One of the oldest coalfields
• 🟣  Singrauli, Madhya Pradesh — Major coal reserve
• 🟣  Talcher, Odisha and Korba, Chhattisgarh — Significant reserves

🔎 3.1 What is Petroleum?

• 🟤  Petroleum is a dark, oily liquid with an unpleasant smell.
• 🟤  The word comes from Latin: Petra (rock) + Oleum (oil) = Rock Oil.
• 🟤  Found trapped between rock layers beneath the Earth’s surface and under the seabed.
• 🟤  It is a mixture of hydrocarbons (compounds of hydrogen and carbon).
• 🟤  Often called “Black Gold” due to its immense economic value.

🌊 3.2 Formation of Petroleum

• 🔵  Millions of years ago, tiny sea organisms died and settled at the sea bottom.
• 🔵  Their remains were covered by layers of sand and silt.
• 🔵  Heat, pressure, and bacterial action over millions of years converted them into petroleum.
• 🔵  Petroleum collected in porous rock layers trapped between non-porous rocks.
• 🔵  Natural gas (lighter) floats above petroleum; salt water (heavier) lies below.

🔬 3.3 Refining of Petroleum — Fractional Distillation

• 🟣  Crude oil is heated in a furnace and vapours pass into a tall fractionating column.
• 🟣  The column is HOT at the bottom and COOL at the top.
• 🟣  Different components condense at different heights based on their boiling points.

🗺️ 3.4 Major Oil Fields in India

• 🔵  Natural gas is found above petroleum in rock traps beneath the Earth’s surface.
• 🔵  It is primarily Methane (CH₄) with small amounts of ethane, propane, and butane.
• 🔵  When compressed under high pressure, it becomes CNG (Compressed Natural Gas).

📊 Coal vs Petroleum vs Natural Gas — Big Comparison

Petroleum and natural gas are not just fuels — they are raw materials for making thousands of useful products called petrochemicals.

🌍 7.1 Environmental Damage from Fossil Fuels

• 🔴  Global Warming: Burning fossil fuels releases CO₂ which traps heat → rising Earth temperatures.
• 🔴  Acid Rain: Coal releases SO₂ and NOₓ → react with water vapour → sulphuric & nitric acid → damages crops, buildings, ecosystems.
• 🔴  Air Pollution: Soot and particulate matter cause respiratory diseases, smog, and haze.
• 🔴  Water Pollution: Oil spills during transport harm marine life and contaminate water bodies.
• 🔴  Land Degradation: Coal mining causes deforestation, soil erosion, and habitat destruction.

♻️ 7.2 Conservation of Fossil Fuels

🔑 Key Terms — Quick Glossary

📝 Try answering before looking at the answer!

📋 Worksheet 1: Fill in the Blanks

Instructions: Fill in the blanks with the correct word/term.

1. Coal, Petroleum, and Natural Gas are called ___________ fuels.
   Ans: Fossil
2. The process by which dead plant material is converted into coal is called ___________.
   Ans: Carbonisation
3. ___________ type of coal has the highest carbon content and is the best quality.
   Ans: Anthracite
4. The separation of crude oil into useful fractions at a refinery is done by ___________.
   Ans: Fractional Distillation
5. CNG stands for ___________ and is mainly composed of ___________.
   Ans: Compressed Natural Gas; Methane (CH₄)
6. The black thick liquid obtained from coal containing 200+ substances is called ___________.
   Ans: Coal Tar
7. ___________ is the residue of petroleum distillation used for road surfacing.
   Ans: Bitumen (Asphalt)
8. LPG is a mixture of ___________ and ___________ gases.
   Ans: Propane and Butane
9. The oldest oil field in India is located at ___________ in Assam.
   Ans: Digboi
10. Coal and petroleum are ___________ natural resources as they cannot be replenished quickly.
    Ans: Exhaustible

✅ Worksheet 2: True or False

Instructions: Write True or False for each statement.

1. Coal was formed from ancient marine organisms.
   ❌ False — Coal formed from ancient land plants. Petroleum formed from marine organisms.
2. Anthracite is the lowest quality coal.
   ❌ False — Peat is the lowest quality. Anthracite has the highest carbon content and quality.
3. Coke is used in the iron and steel industry.
   ✅ True — Coke acts as a reducing agent in blast furnaces to extract iron from iron ore.
4. Kerosene is used as jet fuel.
   ✅ True — Refined kerosene (ATF — Aviation Turbine Fuel) powers jet aircraft engines.
5. Natural gas is found below petroleum under the Earth’s surface.
   ❌ False — Natural gas is LIGHTER and floats ABOVE petroleum in the rock trap.
6. Bitumen is used for road surfacing.
   ✅ True — Bitumen (asphalt), the black solid residue of petroleum, is used to tar roads.
7. CNG is the cleanest burning fossil fuel available.
   ✅ True — CNG burns most cleanly with least pollution among all fossil fuels.
8. Mumbai High is the largest coalfield in India.
   ❌ False — Mumbai High is India’s largest PETROLEUM field. Largest coalfield is Jharia, Jharkhand.
9. Coal tar is used to make medicines, dyes, and explosives.
   ✅ True — Coal tar is a source of 200+ chemicals including drugs, dyes, TNT explosives.
10. Burning fossil fuels contributes to global warming.
    ✅ True — Burning fossil fuels releases CO₂ which traps heat in the atmosphere causing global warming.

📖 Worksheet 3: Short Answer Questions

Instructions: Answer each question in 2–3 sentences.

1. What is carbonisation? How does coal form?
   Ans: Carbonisation is the process by which dead plant matter is slowly converted into coal over millions of years under high heat and pressure. Ancient forests were submerged under water, covered by sediment, and over time the organic matter transformed into coal — a carbon-rich solid fuel.
2. What is fractional distillation? Why is it used for petroleum?
   Ans: Fractional distillation separates a mixture of liquids by heating them and collecting vapours that condense at different temperatures. It is used for crude petroleum because it is a complex mixture of many hydrocarbons — each fraction (petrol, kerosene, diesel etc.) has a different boiling point and condenses at a different height in the fractionating column.
3. Name four products obtained from coal and their uses.
   Ans: (1) Coke — used in iron and steel industry. (2) Coal Tar — source of 200+ chemicals including dyes, drugs, and naphthalene. (3) Coal Gas — used as industrial fuel. (4) Ammonia — used in making fertilizers.
4. What is the difference between CNG and LPG?
   Ans: CNG (Compressed Natural Gas) is mainly methane (CH₄), compressed under high pressure, and used primarily in vehicles and industries. LPG (Liquefied Petroleum Gas) is a mixture of propane and butane, stored as liquid in cylinders, and used primarily as cooking fuel. Both are cleaner than coal.
5. Why are coal and petroleum called exhaustible resources?
   Ans: Coal and petroleum took millions of years to form from ancient organisms under extreme heat and pressure. Once consumed, they cannot be replenished within a human lifetime. Since our rate of consumption is far greater than the rate of formation, they are classified as exhaustible (non-renewable) resources.
6. Name four fractions from petroleum and their uses.
   Ans: (1) Petrol — fuel for cars and motorcycles. (2) Kerosene — jet fuel and cooking stoves. (3) Diesel — fuel for trucks, buses, and trains. (4) Bitumen — road surfacing and waterproofing.
7. How does burning fossil fuels cause acid rain?
   Ans: When coal and petroleum are burned, they release sulphur dioxide (SO₂) and nitrogen oxides (NOₓ). These gases react with water vapour in the atmosphere to form sulphuric and nitric acids, which fall as acid rain. Acid rain damages forests, crops, buildings, and aquatic ecosystems.
8. What is coke? How is it obtained from coal?
   Ans: Coke is nearly pure carbon — a hard, grey, porous solid obtained by heating coal strongly in the absence of air (destructive distillation). It has a very high carbon content, burns at high temperature, and is used as a reducing agent in blast furnaces to smelt iron ore into iron for the steel industry.
9. List four ways to conserve fossil fuels.
   Ans: (1) Use public transport or carpool to reduce petrol/diesel consumption. (2) Switch to renewable energy sources (solar, wind) for electricity. (3) Use energy-efficient appliances (LED bulbs, 5-star ratings). (4) Use CNG or LPG instead of coal as they burn more efficiently and cause less pollution.
10. Why is natural gas called the cleanest fossil fuel?
    Ans: Natural gas is primarily methane (CH₄). When burned, it produces only carbon dioxide and water — much less CO₂ per unit of energy compared to coal or petrol. It produces virtually no SO₂, almost no particulate matter, and minimal nitrogen oxides, making it by far the cleanest burning fossil fuel.

🔗 Worksheet 4: Match the Following

Instructions: Match Column A with the correct option from Column B.

🤔 Worksheet 5: Give Reasons

Instructions: Explain the reason for each observation in 2–3 sentences.

1. Fossil fuels should be used judiciously.
   Reason: Fossil fuels are exhaustible and took millions of years to form. Once consumed, they cannot be replaced in a human lifetime. Wasteful use depletes them rapidly, threatens future energy security, and causes serious environmental pollution including global warming and acid rain.
2. CNG is preferred over petrol and diesel in vehicles.
   Reason: CNG burns much more cleanly than petrol or diesel, producing significantly less CO₂, virtually no SO₂, and minimal particulate matter. This reduces air pollution in cities. CNG is also cheaper per kilometre. Delhi mandated CNG in all public transport to combat severe smog.
3. Coal tar is considered a very valuable industrial material.
   Reason: Coal tar is a complex mixture from which over 200 different substances can be extracted, including dyes, drugs (aspirin), explosives (TNT), perfumes, paints, waterproofing agents, and naphthalene. Its enormous range of industrial applications makes it extremely valuable despite being a by-product.
4. Petroleum is also called ‘Black Gold’.
   Reason: Petroleum is black in colour and immensely valuable. It powers all vehicles and industries worldwide, and provides raw materials for thousands of products including plastics, medicines, fertilizers, and synthetic fibres. Like gold, it is precious, limited in supply, and drives global economies.
5. Natural gas is found above petroleum in underground reserves.
   Reason: Natural gas is mainly methane (CH₄), which has a very low molecular weight and density compared to liquid petroleum. Being much lighter, it naturally rises and accumulates above the petroleum layer in the rock trap. This is why natural gas is often encountered first when drilling for oil.
6. Lignite is not preferred over anthracite as a fuel.
   Reason: Lignite has a lower carbon content (~70%) and higher moisture content compared to anthracite (~90–95% carbon). It produces less heat per unit mass, generates more smoke and ash, and is less efficient. Anthracite burns hotter, cleaner, and more efficiently, making it the preferred industrial fuel.
7. Oil wells do not need pumps when first drilled.
   Reason: When an oil well is first drilled, petroleum underground is under immense natural pressure from compressed natural gas trapped above it. This pressure is sufficient to push petroleum up the drill pipe to the surface without pumps. Only after pressure reduces does artificial pumping become necessary.
8. Burning coal is more harmful to the environment than burning natural gas.
   Reason: Coal contains sulphur, nitrogen compounds, and ash along with carbon. Burning coal releases large amounts of CO₂, SO₂, NOₓ, and particulate matter (soot), causing global warming, acid rain, and severe air pollution. Natural gas (methane) burns cleanly, releasing only CO₂ and water with negligible other pollutants.
9. Naphthalene balls are a product of coal, not petroleum.
   Reason: Naphthalene balls are obtained from Coal Tar, not petroleum. Coal tar is produced during the destructive distillation of coal. It is a complex mixture from which over 200 substances including naphthalene (C₁₀H₈) are extracted. Naphthalene sublimes slowly at room temperature, releasing vapours that repel moths and insects.
10. We should switch to renewable sources of energy.
    Reason: Fossil fuels are finite — they will eventually run out — and cause serious environmental damage including global warming, acid rain, and air pollution. Renewable energy sources like solar, wind, and hydroelectric energy are inexhaustible, produce no harmful emissions, are sustainable, and ensure long-term energy security for future generations.