When a liquid evaporates, its molecules at the surface gain enough energy to escape the attractive forces of the liquid and become vapor. This process requires energy and is influenced by several factors, including temperature, pressure, and surface area. Blowing air over a liquid aids evaporation by increasing its surface area.
When air is blown over the surface of a liquid, it creates a flow of air that disturbs the boundary layer of the liquid, which is the layer of still air that surrounds the liquid surface. This movement of air creates turbulence at the surface, which in turn increases the surface area of the liquid that is exposed to the air. The increased surface area allows more molecules to escape from the liquid and become vapor, which increases the rate of evaporation.
The other options given in the question are not true for the reason why blowing air over a liquid aids evaporation. Blowing air over a liquid does not decrease its vapor pressure, which is the pressure exerted by the vapor of a substance in equilibrium with its liquid phase at a given temperature. Increasing the temperature of a liquid can increase the rate of evaporation, but it is not related to the process of blowing air over the liquid. Similarly, decreasing the density of a liquid does not aid evaporation.