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June 17, 2010 19:34Coke and ice-cubesI was drinking coka-cola the other day with some friends. We had two glasses. One with ice-cubes and one without. We noticed that the one without the ice-cubes froths slightly, which means that it releases gas, wheras the one with the ice-cubes releases a lot more. Since the temperature is lower in the glass with the ice-cubes, and the solubility of gas in water reduces when temperature increases, shouldn't it be the other way round? Does the preasure change because of the sudden change of temperature? |
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One question - did it froth as you poured the coke into the glass?
Just because gases solubility in liquids is reduced when cold, could it be that the gas in the "warmer" glass has been released so quickly, you haven't been able to observe it in what we call "frothing"? What I mean is, you can't see a lot of foam because the gas is almost instantly released into the atmosphere, therefore preventing itself from "gathering" in the liquid's surface. I'm not sure about that, though, I just made a thought!
Ok put it this way. Because I thought of that (and seriously, I hate it when my coke loses all of its gas) so I decided to try something else so that it wouldn't froth so much, but still become colder. I poured the coke from the bottle (which was at room temperature) in my glass (also in room temp). It frothed slightly as it always does when you poor coke from the bottle somewhere else. And then I carefully added the ice-cubes. It frothed like mad! and I was really disappointed! And that's when the thought entered my head... Maybe it's got nothing to do with the temperature, or maybe the sudden change makes it froth. The second is most likely, but still... why does that happen?
Yes, what I said is that the gas may have "had to be released" anyway. But the cold temperature "binds" the gas in what you call "froth"... But as you said, it may not have to do just with temperature. Did you try to add something other than ice cubes to the glass?
Natalia is right. The temperature cannot change so quickly because of some ice cubes. Many minutes would pass till the coke gets colder because of them.
However, what changes IMMEDIATELY is PRESSURE! Try to put something else in it as Natalia said, even your finger (wash it first of all... :P ). If we are wrong, we will think of something else.
I thought of that too! That's why I put a spoon in the glass quite quickly so that it would sort of imitate the ice-cube. Nothing happened... Well, it did froth slightly as I said before when I poored the coke in a room temperature glass, but not like it did when I added the ice-cubes. Also, I was careful when adding the ice. I didn't just throw them in...
So, what could it be? Maybe I was wrong and didn't observe the glass carefully... Or maybe I don't remember clearly. I'm affraid we've ran out of coke so I can't examine the "experiment" again. Maybe someone else could do it?
It must be the temperature of what you throw in the coke. I did the experiment.
- In one glass a throw in the coke a biscuit... Nothing happened.
- In one other glass I throw an ice-cube. It frothed a lot, as you said.
- In the other I throw some ice-cream. The result was the same with this of the case of the ice-cube.
I think I know what happens:
When we place in the glass an ice cube, only the SURFACE of the coke changes its temperature IMMEDIATELY. So, the surface of the coke becomes colder than the coke at the bottom of the glass. That means that the pressure at the surface is bigger than this at the bottom. This difference of pressure causes a stream and because of this gas is released.
Hm... coke with ice-cream and biscuits... My idea will make me rich! :D
Eww... Sorry for that but I wouldn't eat/drink anything like that. I wonder how you managed to do the experiment, I wouldn't be able not to eat the biscuit! :-P Hehe
Your theory seems the "most" correct so far.
Great job Orfea! ;-) I'm glad you went through all of that to make such a... tasty (?) experiment!
I think you're right, although I'm not sure I understand your explanation 100%... Could you explain the last part of your answer? "This difference of pressure causes a stream and because of this gas is released."
An area around the ice-cube will "shrink" for a little because of its contact with something colder (ice-cube), giving space to the liquid deeper than the surface, which will come up, surrounding the "shrank" part of the liquid, and release its gas because of the velocity it gained.
However, it might have something to do with the electric charge of ice. Give me some time to find out.