Step 1: Understanding the Question:
The goal is to classify the given fuels into primary and secondary categories.
A primary fuel is one that is found in nature and can be used directly.
Step 2: Detailed Explanation:
Primary Fuels:
These are natural fuels that occur in the Earth's crust or as biological matter. They do not require chemical processing before they are considered a fuel source.
Examples include:
- Coal: A fossil fuel mined from the ground.
- Petroleum (Crude Oil): Found in underground reservoirs.
- Natural Gas: Found along with petroleum.
- Wood: Obtained directly from trees.
Secondary (Derived) Fuels):
These are fuels obtained from primary fuels through physical or chemical processing. They are usually cleaner or more efficient than the parent primary fuel.
Examples include:
- Coke: It is obtained by the destructive distillation of coal (heating coal in the absence of air). It is a grey, hard, and porous fuel with high carbon content.
- Charcoal: Obtained from wood.
- Petrol/Diesel: Obtained by refining petroleum.
- Coal gas / Water gas: Derived from coal.
Conclusion:
Since Coke is a manufactured product derived from the primary fuel Coal, it is classified as a secondary fuel, not a primary fuel.
Step 3: Final Answer:
Coke is not a primary fuel; it is a secondary fuel derived from coal through destructive distillation.