The SO and I had a party last night, and this morning we discovered that the vodka was left uncapped in the freezer all night. Will this affect the alcohol content in that bottle? Why?
Yes, eventually, but I don’t think you need to worry about the alcohol content of your bottle until it’s been there a few months. It’s a slooooow process.
ETA: Why? It’s in your thread title. Evaporation. But as I said, at that temperature, it’s slooooow.
The “Why” is just that the alcohol will evaporate faster than the water.
There’s really only one way to find out how good it still is.
I bet it would evaporate faster while there’s a party going on at your house than after everyone else has gone home and it’s just you there…
When I first read the title I was already laughing thinking that the question would be to confirm “my frields told me it must have evaporated (
;))”
Drink two shots and post back here. We’ll let you know if the alcohol has evaporated.
Yes, but what’s your point? The ice is still in the bottle. The evaporated alcohol can leave the bottle.
The ice will also slowly evaporate (or at least it will in my freezer), so it’s a question of whether the ice or ethanol evaporate faster.
So…the concensus is that I can still have a martini this evening? 
I think the consensus is, “Why wait?”
The consensus is that you can have a martini only if you also have a bottle of gin that you have not yet mentioned.
The proper chemistry term for ice (or any other solid) “evaporating” is “sublimation”.
Nit picked.
ETA: The consensus seems to me to be “drink it fast, before it loses any more potency”!