# Alcohol in beer would evaporate extremely slowly in cold temperatures?

## Main Question or Discussion Point

I'm guessing the alcohol in beer would evaporate extremely slowly in cold temperatures like a fridge. I hear a lot of people say otherwise, so I'm wondering if it even evaporates a noticeable amount in 24 hours?

It depends on the conditions inside the fridge.

If the fridge is airtight, then the worst-case scenario is that equilibrium is achieved and the entire fridge becomes filled to saturation with ethanol vapors. The vapor pressure of ethanol at 4°C is about 0.02 atmospheres, so if the interior of the fridge has a volume of 1 cubic meter, the amount of ethanol vapor at equilibrium is PV/RT = 0.9 mol, or 40 g. So it is theoretically possible that you could lose all the ethanol as long as your beer has less than 40 g of ethanol in it (probably the case unless you have put a lot of beer in the fridge).

But that is the worst-case scenario, and it will take a long time to achieve equilibrium unless you have dispersed the beer into an aerosol.

I would guess, roughly, that the concentration would not be noticeably changed after 24 hours, but probably would be after a week. Here is an example of a similar (informal) experiment. Of course, you could prevent even this by simply covering the beer.

SteamKing
Staff Emeritus
Homework Helper
I'm guessing the alcohol in beer would evaporate extremely slowly in cold temperatures like a fridge. I hear a lot of people say otherwise, so I'm wondering if it even evaporates a noticeable amount in 24 hours?
Is that why it's hard to keep beer in a refrigerator? People drink it up before it evaporates?

Borek
Mentor
Who keeps their beer opened?

SteamKing
Staff Emeritus