How is this possible?

[thechairman]

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http://www.metacafe.com/watch/405950/bar_trick_with_whiskey_and_water/

i was taking a break from studying and i watched this video, about whiskey and water changing places. now being the inquisitive medical mind that i am, i am now wondering how this is even possible. since both ethanol and water can hydrogen bond with each other, how can they even seperate out to from distinct phases?

 

[DrMT]

density?

 

[thechairman]

yeah i could see it happening for an oil, but shouldn't the hydrogen bonding of water and ethanol prevent this from happening? or have the merits of hydrogen bonding been blown way out of proportion in my chemistry and biology classes, and it's not really that srong.

 

[estairella]

If you slosh salt into a container of water (not enough to get saturated), you get a saline solution with a uniform density greater than water alone. If however, you gently and very slowly pour a small stream of salt (same amount) towards the side of the container, the salt will not dissolve but collect at the bottom (salt is denser). In fact, you will set up a gradient with high density at the bottom (salt + strong saline solution) and low density at the top (water + weak saline solution).

This is basically the same idea... slosh water (higher density) into whiskey (lower density) and the two will mix. Slowly add one to the other and the mixing will be minimal, instead, water, because it is more dense, will sink to the bottom and the ethanol/water mixture (whiskey), because it is less dense, will rise.

Also, I'm not sure why hydrogen bonding would have a disruptive affect - ethanol can hydrogen bond with itself.. (in fact, except when they form an azeotrope I think at 95% ethanol/5% water, you are able to separate water and alcohol by simple distillation - showing that they can be separated)

 

[RedSHIFT]

it's most likely a result of density. I'm pretty sure the reverse of the trick would not work. Meaning that if the whiskey was placed on top of the water the trick would not work. The trick is dependent on water being placed on top.

 

[xrevision]

it also has to do with rss which is relative super saturation, you learn about that in analytical chemistry.

 

[jon stewart]

the new MCAT for 2008.......

watch a bunch of youtube videos with cool/random/bizzare things going on. Then explain the science behind it!

Lets hope they have broadband at Thompson....otherwise i can already hear people complaining.