I have recently added alcoholic Baileys/vodka to hot chocolate and coffee. The boiling point of ethanol is 70C, does the alcohol boil off?
In: Chemistry
Liquids also evaporate at temperatures below their boiling point. The hotter they are, the faster they evaporate. So while it’s true that ethanol has a lower boiling point than water, even if you raise the temperature of the liquid above the boiling point of ethanol, it’s not just the ethanol that’s going to evaporate. Both water and ethanol will evaporate, just at different rates. The longer you keep the liquid at this temperature, the weaker the ethanol concentration becomes (because you’re losing ethanol faster than water), but also the less liquid will be left in total.
To boil off most of the alcohol you’d have to keep it at a high temperature for a long time. Stirring Baileys (or other types of booze) into a hot drink will not lead to much alcohol loss because the drink won’t be that hot to begin with (probably just around 70C), will cool down by the addition of the Baileys, and will cool down further as time passes.
did some of it boil off? yes.
did all of it boil off? no
how much? depends on how hot your coffee/hot cocoa was. how MUCH of it there was. how much baileys/vodka did you put in. what temperatur of baileys vodka did you put in.
The USDA actually did a study on this about a decade ago. You can find the relevant results here on page 12:
https://www.ars.usda.gov/ARSUserFiles/80400525/Data/retn/retn06.pdf
TLDR when stirring baileys (or any liquor) into a hot drink, you lose about 15% of the ethanol.
Edit: clarity
Some evaporates into thestill air above to be in balance with what is in the liquid, but the liquid cools as it evaporates slowing the evaporation too and making the amount needed to be in balance smaller. It can also only evaporate from the exposed top, and how much evaporated alochol is in the still air above the liquid is in balance with what is in the liquid. So time, concentration, and temperature limit how much evaporates. Same idea as a pot of boiling water. If you leave it open it takes time to boil away. If you cover it it will not boil dry anytime soon.
A typical hot cup of coffee is served around 70C (160F) and that’s generally too hot for most people to do more than sip at until it’s cooled a bit. An extra hot cup might be served around 80C (180F or so), but that’s something that most people will leave in the cup while they drive to work, so that it’ll still be warm when they get there – though I guess some people might like to sip scalding hot coffee.
Point being, most coffee is served just around the boiling point of alcohol, or maybe slightly higher. But if you’re adding room temperature Baileys to a hot drink, you’re cooling it off a bit, so the overall temperature of your boozy coffee is likely going to end up a shade south of that boiling point, leaving it warm, but with the alcohol intact. Certainly a bit of the alcohol might burn off while it’s cooling down from that temperature, but you’d need to continue adding heat (like boiling it on a stovetop) to actually burn off all of the alcohol.
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