Dry Tarn: some questions about evaporation and latent heat

 

We found the elusive Dry Tarn on Great Gable. It is easier to see coming down than going up because of the way it sits. I was going to calculate the energy needed to make it evaporate using the specific latent heat equation I am teaching my classes but I've realised there's a problem. In the simplified world of GCSE Physics, we calculate the energy required to raise the temperature to boiling point and then the energy to change state. The problem here is that the water evaporates without ever getting close to boiling point. This gave me some clues. I've blogged about boiling point on Great End and it is very close to that at sea level. Dry Tarn evaporates when it is dry for long periods. That must mean when the humidity is very low. Even so, saying that the most energetic particles can escape when if you wait long enough, they all escape ... is this going to be a probability problem in the end?