Coal and Petroleum — NCERT Solutions, AI Tutor & Practice

Understand: Natural resources are materials obtained from nature that are useful to us.

Analyze:

• Exhaustible natural resources: These are present in limited quantity in nature and can get used up by human activities. Examples: coal, petroleum, natural gas, minerals, forests.
• Inexhaustible natural resources: These are present in unlimited quantity and are not likely to be exhausted by human use. Examples: sunlight, air, water (in the broad sense).

Conclude: Coal and petroleum are exhaustible resources, so they must be used wisely, while sunlight and air are inexhaustible.

Understand: Coal is a fossil fuel formed from the remains of ancient plants.

Analyze (formation):

1. Millions of years ago, dense forests grew in low-lying wetland areas.
2. Due to natural processes like flooding and earthquakes, these forests got buried under the soil.
3. As they sank deeper, they were exposed to high temperature and high pressure.
4. Over a very long time, the buried plant matter was slowly converted into coal.

Conclusion (Carbonisation): The slow process of conversion of dead vegetation into coal under high temperature and pressure is called carbonisation. Since coal is formed from the remains of living organisms (plants), it is called a fossil fuel.

Understand: When coal is heated strongly in the absence of air, it gives several useful products.

Analyze — the products:

1. Coke: A tough, porous, black solid that is almost pure carbon. Used in the manufacture of steel and in the extraction of metals.
2. Coal tar: A black, thick liquid with an unpleasant smell, a mixture of about 200 substances. Used to make synthetic dyes, drugs, explosives, perfumes, plastics, paints, roofing materials, and naphthalene balls.
3. Coal gas: Obtained during the processing of coal to get coke. Used as a fuel in many industries.

Conclude: Coal is thus not only a fuel but also a source of many valuable raw materials.

Understand: Petroleum is a dark, oily liquid fossil fuel found deep beneath the earth.

Analyze (formation and occurrence):

• It was formed from the remains of tiny sea plants and animals that died and settled at the bottom of the sea millions of years ago.
• These remains got covered with layers of sand and clay, and under high temperature and pressure they were slowly converted into petroleum and natural gas.
• Petroleum is found trapped between rock layers, with natural gas above it and water below.

Conclude: Petroleum and its many products (petrol, diesel, kerosene, LPG, lubricants, etc.) are so useful and valuable that petroleum is called 'black gold' — 'black' because of its dark colour and 'gold' because of its great economic value.

Understand: Petroleum extracted from the earth is a mixture of many useful substances and cannot be used directly.

Analyze (refining): Petroleum refining is the process of separating the various components (fractions) of petroleum in a refinery, based on their different boiling points, by fractional distillation.

Some fractions and their uses: | Fraction | Use | |---|---| | Petrol (Petroleum gas / LPG) | Fuel for cooking (LPG), motor fuel | | Kerosene | Fuel for stoves, lamps, jet aircraft | | Diesel | Fuel for heavy vehicles, electric generators | | Lubricating oil | Lubrication of machine parts | | Paraffin wax | Ointments, candles, vaseline | | Bitumen | Paints, road surfacing |

Conclude: Refining turns crude petroleum into many separate, directly usable products.

Understand: Natural gas is an important fossil fuel found above petroleum deposits and also in separate reserves.

Analyze:

• Natural gas can be stored under high pressure as Compressed Natural Gas (CNG).
• When supplied to homes and factories through pipelines, it is called PNG (Piped Natural Gas).

Advantages of CNG/PNG:

1. It is a cleaner fuel — it burns with less pollution and produces very little smoke.
2. It can be supplied directly through pipelines, so it can be used continuously without storing cylinders.
3. It is a more efficient fuel and can be used for power generation.

Conclude: Because it is clean and convenient, CNG is now widely used as a fuel for vehicles.

Understand: Both coal and petroleum are burnt to release energy.

Analyze (why fossil fuels):

• They were formed from the remains (fossils) of dead plants and animals buried under the earth millions of years ago.
• Because they come from once-living organisms, they are called fossil fuels.

Why conserve them:

1. They are exhaustible — present in limited amount and will get used up.
2. Their formation takes millions of years, so once finished they cannot be replaced in our lifetime.
3. Burning them causes air pollution and contributes to global warming.

Conclude: Since they are limited and non-renewable, we must use them carefully and look for alternative energy sources.

Understand: PCRA (Petroleum Conservation Research Association) advises people on how to use petrol and diesel efficiently.

Analyze — PCRA tips:

1. Drive at a constant and moderate speed as far as possible.
2. Switch off the engine at traffic lights or when the vehicle is stationary.
3. Ensure correct tyre pressure in the vehicle.
4. Get the vehicle serviced (maintained) regularly.

Conclude: Following these simple habits saves fuel, saves money, and reduces pollution.

Understand: All three are obtained when coal is processed to make coke.

Analyze — comparison table: | Product | Physical state | Main use | |---|---|---| | Coke | Solid (grey-black, porous) | Making steel, extracting metals | | Coal tar | Liquid (thick, black) | Making dyes, plastics, paints, naphthalene balls | | Coal gas | Gas | Used as a fuel in industries |

Conclude: From a single source — coal — we obtain a solid, a liquid, and a gaseous product, each with important industrial uses.

Understand: These questions test the properties and advantages of fuels.

Analyze:

(a) Fossil fuels (coal, petroleum, natural gas) form from the buried remains of organisms over millions of years under high temperature and pressure. Once used up, they cannot be reformed within a human lifetime. Because they cannot be replaced as fast as they are consumed, they are called non-renewable.

(b) LPG is preferred over wood because:

1. LPG burns completely and cleanly, producing little smoke, while wood produces a lot of smoke and pollution.
2. LPG has a high calorific value, so it gives more heat.
3. Burning wood cuts down trees and harms the environment; LPG is more convenient and does not leave ash.

Conclude: Fossil fuels must be conserved, and cleaner fuels like LPG are better for both health and the environment.

Understand: The claim assumes fossil fuels are being replaced as fast as we consume them.

Analyze:

• Fossil fuels do form in nature, but the process takes millions of years of high temperature and pressure acting on buried remains of organisms.
• We consume them extremely rapidly — much faster than they can ever form.
• They are therefore classified as exhaustible (non-renewable) resources.
• Burning them also causes pollution and global warming.

Conclude: I do not agree with the student. Since fossil fuels form far too slowly and exist in limited amounts, using them freely would exhaust them. They must be conserved and used judiciously, and we should shift to renewable sources like solar and wind energy.

Understand: Since coal and petroleum are exhaustible, everyone should try to save them.

Analyze — ways to conserve:

1. Use public transport, carpool, or cycle instead of individual vehicles to save petrol and diesel.
2. Switch off electric appliances and lights when not in use (since much electricity is generated from coal).
3. Use energy-efficient appliances and pressure cookers for cooking to save fuel/LPG.
4. Maintain vehicles properly and switch off engines at signals to reduce fuel wastage.
5. Use renewable energy sources like solar cookers and solar water heaters where possible.

Conclude: Small, mindful habits by each person together save large amounts of these precious fossil fuels for the future.