What is the primary hazard that justifies covering the apparatus when using ethanol?

• A. Ethanol is volatile.
• B. Ethanol is explosive.
• C. Ethanol is non-flammable.
• D. Ethanol is harmless.

Answer: (A)

Volatility and the vapour hazard from flammable liquids. Ethanol has a relatively low boiling point, so it evaporates easily and forms flammable vapour even at room temperature. Covering the apparatus helps keep that vapour from escaping into the surrounding air, reducing both inhalation risk and the chance that any vapour will ignite if it meets a flame or spark. So the primary hazard is that ethanol is volatile and can produce flammable vapour, which is why a cover is used. The other statements don’t fit as well: ethanol isn’t non-flammable or harmless, and while vapour can be dangerous, the direct reason for covering is to limit evaporation and vapour formation.