Originally posted by sonhouse
The idea of evaporation inside a can, even if it takes place, wouldn't a total temperature change violate the law of conservation of energy?
I had missed the post where you reported the results and only just seen it. So it appears that there is a genuine temperature drop. I can't think of any possible way in which your readings could have gone wrong to the point of falsely reporting a drop.
If the cooling is due to evaporation (which I think is by far the best explanation at this point), then it isn't a violation of the conservation of energy. If you left the can to sit for a while till the liquid starts condensing again, it will heat up. A fridge depends on this principle.
A liquid contains something similar to chemical bonds. They are weaker than the well known covalent, ionic and metallic bonds, and they can swap partners but they are very real. When evaporation takes place, the bonds are being broken and potential energy is being created.
Maybe 'bonds' isn't the right word:
https://en.wikipedia.org/wiki/Intermolecular_force