Ethanol's Advantage: Clean Combustion

The question asks which property makes ethanol a better alternative fuel compared to petrol. The key advantage lies in its combustion characteristics.

Analyzing Fuel Properties

• Option 1: Ethanol is a solid fuel
  This is incorrect. Ethanol is a liquid at standard temperature and pressure, similar to petrol.
• Option 2: Ethanol burns with a clean, smokeless flame
  This is correct. Ethanol combustion produces significantly fewer pollutants like carbon monoxide and particulate matter compared to petrol. It burns more completely, leading to a cleaner burn and reduced environmental impact. This cleaner burning is a major reason it's considered a better alternative.
• Option 3: Ethanol has a higher boiling point than petrol
  While ethanol's boiling point (approx. 78°C) is within the range of petrol's boiling points (approx. 40-205°C), this difference is not the primary factor making it a superior alternative fuel in terms of environmental benefit or performance.
• Option 4: Ethanol produces harmful smoke when burned
  This is incorrect. It is the opposite of ethanol's advantage; it burns much cleaner than petrol, producing less harmful smoke and emissions.

Conclusion on Alternative Fuel Properties

Ethanol's ability to burn cleanly and with minimal smoke makes it an environmentally preferable alternative to petrol. This property directly addresses pollution concerns associated with traditional fossil fuels.