My name is Maria and I am a physics teacher in Greece. (My English are not very good, so I am sorry for my mistakes).
I am trying to find a qualitative simulation about evaporation and condensation of water from an open and closed container.
I want my students to see what is going on (microscopically) in an open and closed container.
Letís say that there is an open container with water at temperature T. There are some molecules of water that have enough kinetic energy to escape from the liquid and became water vapor (gas). This procedure (the conversion from liquid state to gas state) is called evaporation and goes on at all temperatures. Due to evaporation the level of the liquid in the open container decreases.
The rate of evaporation depends only by the temperature of water.
At high temperature lots of molecules have enough energy to escape from the liquid. At low temperature fewer molecules have sufficient energy to escape from the liquid.
The wind, the air temperature, the humidity etc play no role at this procedure! The rate of evaporation [the number of the molecules that convert from liquid to vapor is constant at a given (and constant) temperature].
All the simulations / videos etc that I have found, except of temperature, claim that the rate of evaporation depends on wind, humidity etc. This is only true when we talk about net evaporation.
If there is a close container with some water, the following procedures take place.
Initially, the system contains only liquid, and air above it. As evaporation starts (the rate of evaporation is constant for the specific temperature of the water), the molecules from the surface of the liquid escape into vapour state, in the confined space above. Therefore, the level of liquid falls.
Then starts the process of condensation. This is the conversion of vapour into liquid. Initially, escaped molecules (from liquid state) move randomly in all directions and collide with one another. As more and more molecules enter the confined space, some slow-moving molecules are pushed back. They collide with the surface of the liquid to reconvert into liquid.
In the initial stages, the rate of evaporation (constant) is more than the rate of condensation because only small number of molecules are present in the gaseous state. The rate of condensation thereafter gradually increases as the number of molecules in the gaseous phase increases. Finally, a stage is reached when the rate of the two opposing processes is the same.
The state where the rate of evaporation becomes equal to the rate of condensation is called a state of dynamic equilibrium. In such a state, although the amount of liquid level in the container does not change, evaporation has not stopped and the system is not at rest. In fact, the number of molecules, which escape from the liquid to the gaseous phase (due to evaporation), becomes equal to the number of vapour molecules that return to the liquid.
I want my students to understand the above processes at microscopic level and I believe that a qualitative simulation accompanied with a qualitative diagram of the rate of evaporation and condensation with time would be very helpful.
Can you help me?
Thank you very much!