Relative humidity and evaporation

[jmher0403]

Homework Statement

The air is at 50% humidity and the temperature of the surface of the ocean and the air is 20degrees C. What are the two critical processes that must occur to ensure there is continued evaporation in the absence of external energy sources?

Homework Equations

Relative humidity = partial pressure of water vapour in air / vapour pressure

The Attempt at a Solution

I am sure that there would be net evaporation of water until the equiilibrium is reached so that the relative humidity becomes 100%. Surface of ocean and the air is at same temperature so I assume that the temeperature of water must increase so that the relative humidity just above the surface becomes lower but since there is no external energy source, I have no idea...
Please help!

 

[anathema]

it is important to understand the principles of thermodynamics in order to answer this question. The two critical processes that must occur to ensure continued evaporation in the absence of external energy sources are diffusion and convection.

Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration. In this case, water molecules in the air will diffuse to the surface of the ocean, where there is a lower concentration of water molecules. This allows for continued evaporation to occur as long as there is a difference in concentration between the air and the surface of the ocean.

Convection is the transfer of heat through the movement of fluids, such as air or water. In this scenario, convection plays a crucial role in maintaining the temperature difference between the air and the surface of the ocean. As water molecules evaporate from the surface, they take energy with them, causing the surface to cool. This creates a temperature difference between the air and the surface, allowing for continued evaporation to occur.

It is also important to note that the relative humidity of the air will not necessarily reach 100% in this scenario. As long as there is a temperature difference between the air and the surface of the ocean, evaporation will continue to occur. However, once the air and surface reach the same temperature, evaporation will cease.

In summary, diffusion and convection are the two critical processes that must occur to ensure continued evaporation in the absence of external energy sources. These processes work together to maintain a temperature difference between the air and the surface of the ocean, allowing for continued evaporation to occur.