Evaporation rate decreases with reduced surface exposure to air

Steps:

• Identify key factors of evaporation: surface area, temperature, airflow, and vapor saturation above liquid.
• Assess option A: increases airflow, speeding evaporation by removing saturated air.
• Assess option B: raises temperature, increasing kinetic energy and evaporation rate.
• Assess option C: covers surface, preventing vapor escape and reducing net evaporation.
• Assess option D: enlarges surface area, allowing more molecules to evaporate.

Why C is correct:

• Putting a lid creates a closed system where water vapor accumulates, reaching equilibrium with the liquid (per dynamic equilibrium in evaporation-condensation), minimizing net loss.

Why the others are wrong:

• A: Blowing air disrupts boundary layer, accelerating diffusion of vapor away (increases rate per ventilation principle).
• B: Heating boosts molecular energy, raising vapor pressure and evaporation rate (evaporation proportional to temperature).
• D: Larger diameter increases exposed surface area, directly proportional to evaporation rate (rate = k × area).

Final answer: C