1. Define the term 'fuel'. 2. Name any two renewable natural sources of energy. 3.…

1. Define the term ‘fuel’. 2. Name any two renewable natural sources of energy. 3. Define the term ‘carbonisation’. 4. Name the three main products obtained from destructive distillation of coal. 5. State two uses each of the following: (a) asphalt (b) paraffin wax 6. Write the full forms of CNG, LPG and PNG. 1. Describe, in brief, the process of ‘coal formation’. 2. Differentiate between lignite and bituminous coal.

Short answers (direct):
Q1: A fuel is a substance that releases energy (usually heat) when burned or undergoes chemical transformation.
Q2: Two renewable natural energy sources: solar energy and wind energy.
Q3: Carbonisation is the heating of organic material (like coal or biomass) in absence of air to remove volatile matter, producing carbon-rich solid (coke or charcoal).
Q4: Three main products of destructive distillation of coal: coke (or char), coal tar, and coal gas.
Q5: (a) Asphalt — road surfacing and waterproofing (e.g., roofs). (b) Paraffin wax — candle-making and polishing/coating (e.g., furniture or crayons).
Q6: CNG = Compressed Natural Gas; LPG = Liquefied Petroleum Gas; PNG = Piped Natural Gas (sometimes called Pipeline Natural Gas).

Q7: Describe, in brief, the process of coal formation

The correct answer is: Coal forms by the burial and transformation of plant material in anaerobic, swampy environments over geological time.

Explanation and steps:

  1. Plant accumulation: Dense vegetation in ancient swamps and peat bogs dies and accumulates as plant debris (peat) under waterlogged, oxygen-poor conditions that slow decay.
  2. Peat formation: Over time, the plant debris compacts and partially decomposes to form peat (low carbon, high moisture).
  3. Burial and coalification: Layers of sediment bury the peat. Increased pressure and temperature during burial drive off water and volatile compounds and progressively increase carbon content — a process called coalification.
  4. Coal ranks form with increasing depth/temperature/time: peat → lignite (brown coal) → sub-bituminous → bituminous coal → anthracite (highest carbon, hardest).
  5. Final product: The result is coal of varying rank and calorific value used as a fossil fuel and for industrial coke production.

Q8: Differentiate between lignite and bituminous coal

The correct answer is: Lignite is a low-rank, brownish coal with higher moisture and lower carbon content and calorific value; bituminous coal is a higher-rank, black coal with lower moisture, higher carbon content, and greater heating value.

Key differences (side-by-side):

  • Rank and age: Lignite = low rank (younger); Bituminous = middle rank (older).
  • Color & texture: Lignite = brownish, crumbly; Bituminous = dark black, harder/lustrous.
  • Carbon content: Lignite ≈ 25–35% fixed carbon; Bituminous ≈ 45–86% fixed carbon (varies).
  • Moisture & volatiles: Lignite has high moisture and volatile matter; bituminous has lower moisture, moderate volatile matter.
  • Calorific value: Lignite = low (poor fuel efficiency); Bituminous = higher (good for electricity and industry).
  • Uses: Lignite = local power generation (near mines); Bituminous = electricity generation, metallurgical coke (some grades), industrial heating.

If you want, I can make a one-line comparison table or add typical calorific values and examples of countries where each is mined.

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