Question

State the appropriate scientific reasons for the following statement. The rate of evaporation decreases with increase in humidity.

Answer 1

Hint: Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air.

Complete answer:
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. The amount of water vapor needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of air decreases it will eventually reach the saturation point without adding or losing water mass. The amount of water vapor contained within a parcel of air can vary significantly.
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other based on how they collide with each other. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.
When humidity is high, then air is already saturated with water vapours, meaning it has a lot of water vapours. Therefore, it will not take more water vapours easily, Hence, rate of evaporation decreases.

Note:
Relative humidity greatly affects evaporation rates. When it is high, relative humidity slows evaporation; relative humidity reduces it to zero (no evaporation at all) when it reaches 100 percent. Relative humidity is the amount of moisture in the air compared to what the air can "hold" at that temperature.