B How can ice cool an alcoholic drink below 0°C?

[Chestermiller]

Okay, maybe it is one word ... Chet, chemical engineers are supposed to know these things.

Ouch!

 

[russ_watters]

A few additional tests:

 

[russ_watters]

Unfortunately, it was not so obvious to naive me (and many other mere mortals). At least at the beginning, it wasn't obvious to me that, as the ice melted, its temperature would be dropping.

I don't mean to belabour this, but it does seem to be a blind spot in common physics/thermo training. What happens to liquid water exposed to the air (wet bulb temp, evaporative cooling) is not a very different concept, and is discussed in quite a bit of detail in the courses I took. But mixtures of ice and liquids are not discussed (that I can recall). Per Bystander's point, my first exposure to it was on the practical side, making homemade iced cream with my grandparents. So it was something I took for granted long before I had any understanding of why it happened.

Even still, the mechanism behind how a solid block of ice can be melted by cold salt (for example) is tricky...even if we do see it every winter on the roads.

 

[russ_watters]

I completed a calculation with the heat of mixing effect included. The heat of mixing data was somewhat incomplete, and I had to use my best judgment at filling in the blanks. The initial state was a mixture of 44 g EtOH, 56 g water at 20 C, and 150 g ice at 0 C.

As best I could estimate, the final state was a mixture of 44g EtOH, 146 g water, and 60 g ice, all at -14 C.

[previous, without mixing]
Initial state:
100 gm alcohol/water solution, 44% alcohol mass percent at 20 C
100 gm ice at 0 C

Final State:
155 gm alcohol/water solution, 28% alcohol at -18 C
45 gm ice at -18 C

Thanks. You started with more ice when you included the heat of mixing so I can't compare it exactly, but it looks the impact of the heat of mixing was pretty small. That, I expected. What I didn't expect was how much ice was melting and as a result, how much dilution there was. Of course, I also didn't look up the freezing point of ethanol prior to starting to make predictions...

 

[.Scott]

No one's made ice cream?!

That's the key. Those of us who got to make made ice cream when we were kids are familiar with process. In that case it was ice and salt - to generate the extra cold conditions needed to get the mixture to form ice cream.

I think the clearest situation is when both the ice and the alcohol start out at the same temperature. Assuming that the alcohol is 200 proof, any temperature above the freezing point of alcohol and cold enough for ice will work

The alcohol has an affinity for water, and dissolves the ice - forcing into a liquid phase and chilling the entire system.

I don't believe the equilibrium condition has been fully explored. In final equilibrium there will be a liquid alcohol/water mix and a solid alcohol/water mix, and those alcohol/water ratios will not be the same. And, of course, the temperature will be the same throughout.

 

[jbriggs444]

I don't believe the equilibrium condition has been fully explored. In final equilibrium there will be a liquid alcohol/water mix and a solid alcohol/water mix

If you look at post #70 in this thread, DrStupid alludes to fractional crystalization. The frozen material will be pure water.

 

[256bits]

If you want to add booze to your ice-cream, well here you go,
http://gizmodo.com/5860835/how-to-make-alcoholic-ice-cream-the-greatest-dessert-of-all-time

 

[Bystander]

If you look at post #70 in this thread, DrStupid alludes to fractional crystalization.

That's the "jacking," a popular separation method used in the past. History of science is another hobby of mine --- didn't think this was that forgotten, but that's what I get for thinking and chewing gum.

 

[Chestermiller]

I don't believe the equilibrium condition has been fully explored. In final equilibrium there will be a liquid alcohol/water mix and a solid alcohol/water mix, and those alcohol/water ratios will not be the same. And, of course, the temperature will be the same throughout.

I agree with jbriggs444 in post #163 on this. Apparently you hadn't actually seen the phase diagram for EtOH/water when you made this statement.

Have you considered doing some modeling calculations to more fully explore the final equilibrium condition for various initial states? Why don't you run some quantitative cases where you start out with 200 proof alcohol to see how the results compare? That would be pretty interesting.

 

[jim hardy]

I think of it backward. (for me that comes natural )

We usually think of ice warming up to its melting point which we all know is 32F..
But what happens is ,
The drink cools down to its freezing point...
A good Gin & Tonic will frost the glass

 

[gjonesy]

I think of it backward. (for me that comes natural )

We usually think of ice warming up to its melting point which we all know is 32F..
But what happens is ,
The drink cools down to its freezing point...
A good Gin & Tonic will frost the glass

I can remember making Ice cream as a kid and we had this electric churn, it would spin in the ice bucket with the cream mixture inside and we'd always lay a towel over the top thinking it would get colder faster. You could remove the towel and see frozen condensation (frost) on the top of the spinning cream container above the salt/ice line, and this would be in the middle of the summer.

 

[Jon B]

How can ice cool an alcoholic drink below 0°C? Answer: When the ice is massive enough and cold enough to bring the beverage from its present temperature to a temperature below 0°C. Remember, the quality of the answer is based on the quality of the question.

 

[Chestermiller]

]How can ice cool an alcoholic drink below 0°C? Answer: When the ice is massive enough and cold enough to bring the beverage from its present temperature to a temperature below 0°C. Remember, the quality of the answer is based on the quality of the question.

So, are you saying that the ice has to start out below 0 C?

 

[mfb]

How can ice cool an alcoholic drink below 0°C? Answer: When the ice is massive enough and cold enough to bring the beverage from its present temperature to a temperature below 0°C. Remember, the quality of the answer is based on the quality of the question.

The ice does not have to be cold enough, that's the main result we established over the last pages. It can start at 0°C.