Which of the following is used to power steam engines?

Analysis

The question asks for the primary fuel source historically and technically used to generate steam in steam engines. To answer this, we must look at the process of steam generation and the energy sources derived from petroleum and coal.

Concept Explanation

A steam engine works by heating water in a boiler to produce high-pressure steam. This steam then expands to push a piston or turn a turbine, converting thermal energy into mechanical work.

• Coal: This is a solid fossil fuel composed mainly of carbon. When burned, it releases a significant amount of heat energy, making it the traditional and most efficient fuel for heating large quantities of water in boilers for steam engines (such as steam locomotives).
• Lubricating oil: This is used to reduce friction between moving parts of an engine, not as a fuel source.
• Bitumen: This is a thick, sticky form of petroleum used primarily for road surfacing and roofing. It is not suitable as a fuel for steam engines.
• Diesel oil: This is used in internal combustion engines (diesel engines), where the fuel is burned inside the cylinder to create pressure, rather than to heat water for steam.

Step-by-Step Solution

1. Identify the requirement: We need a fuel capable of sustained, high-heat combustion to boil water.
2. Evaluate the options: • A (Lubricating oil): Incorrect. It is a lubricant, not a fuel. • B (Coal): Correct. Historically, coal was the primary fuel used to fire the boilers of steam engines. • C (Bitumen): Incorrect. It is too viscous and heavy for this purpose. • D (Diesel oil): Incorrect. While it is a fuel, it is specifically designed for internal combustion engines, not external combustion steam engines.
3. Conclusion: Coal provides the thermal energy required to convert water into steam in a boiler system.

Exam Tip

When you see questions about fossil fuels in Chemistry, remember their primary uses:

• Coal: Heating and electricity generation (steam).
• Bitumen: Road construction.
• Diesel/Petrol: Internal combustion engines.
• Kerosene: Domestic heating and lighting.