A Bit of a Science Puzzle - Page 2

quarky · 20th June 2012, 01:40 PM

Originally Posted by Ziggurat

I don't think the effect is because of an inability to nucleate ice crystals - after all, beer and soda aren't particularly pure. I think the effect is primarily due to the pressure dependence of the freezing point: since water expands when it freezes, the freezing point drops when you pressurize it. Which also means that the freezing point rises when you depressurize it.

Exactly.
Gas law stuff.
Flip side of pressure cooking.

Glad you said it first, as you have more credibility.

The other explanations get a bit too 'precious'.

DavidS · 20th June 2012, 04:34 PM

Originally Posted by Ziggurat

I don't think the effect is because of an inability to nucleate ice crystals - after all, beer and soda aren't particularly pure. I think the effect is primarily due to the pressure dependence of the freezing point: since water expands when it freezes, the freezing point drops when you pressurize it. Which also means that the freezing point rises when you depressurize it.

As noted already (and without actually consulting data tables) I think water's freezing point is too weak a function of pressure for that to make much difference. Off the top of my head, it's 273.15 K at 1 atm and 273.16 K at ~0.006 atm.

OTOH, dissolved stuff -- like CO2 -- depresses the freezing temperature exactly the same way antifreeze does in your car's radiator. It's not hard to imagine CO2+water in equilibrium several degrees below the freezing point of more-pure water. I can imagine four mechanisms for sudden liberation of CO2 from solution to induce freezing:

- Separation of CO2 into the bubble would freshen the adjacent water, raising its freezing point above the ambient temperature.

- The CO2 phase change would consume some latent heat of vaporization, helping to depress or maintain the low temperature.

- Forming the bubble surface interface film would consume surface energy (work/area), AKA surface tension (force*length/area -> force/length), also depressing or mantaining temperature. Since surface area increases with the square of the bubble diameter, that can be a big energy drain from the tiny liquid volume around a tiny bubble.

- Any ice crystals that form liberate their own latent heat of fusion, but that's partly offset by the energy consumed to create their own phase interfaces. Again, while crystals are tiny that can be a net energy sink.

Alas, I can't cite authoritative reference that these control the observed phenomenon. I shall, however, endeavor to acquire my own independent, if merely qualitative observations. A twelve pack should be a good start, right?

quarky · 20th June 2012, 05:26 PM

Yeah.
12 should do it.

You're making it much too complex.
H2O, under pressure, has a lower freezing point. Relieve the pressure? Presto-chango.

bottsranzee · 20th June 2012, 06:51 PM

Originally Posted by Foolmewunz

Not one I have the answer to, but I'm a notoriously lazy bastage and you sciencey guys have this information stored away in your heads.

I went to peel my son's apple for his lunch box yesterday morning. Every liquid product in the refrigerator was still liquid, e.g. not frozen. That includes milk, soy milk, coca cola, beer, water and something similar to Red Bull. So the temp in the fridge wasn't going haywire.

The apples are in a plastic produce bag in the bottom bins of the fridge. The freezer compartment is at the top and is a separate door (not a combined unit).

On the surface of the apples there were ice crystals. Not like little flakes of frost from a bad freezer, but a thin coating of ice. My immediate reaction, as you can see from the above, was that the fridge must've gotten too cold and everything was frozen or freezing over. But it was just this one product - the apples.

Thus we get to the puzzle. My fallback solution is that there's some sort of chemical or solution that freezes at a much higher temperature than water and that when the apples sweated (they were in a plastic bag), this chemical or solution was still present in enough strength. Alternately, does an apple exude some sort of fume that might combine with moisture and cold air to freeze at that high a temp?

Knowing that someone's going to ask... I tried to replicate the conditions and was hoping to get a picture, but it did not occur this morning when I opened the plastic bag of apples again. Also, I do not have an accurate thermometer handy, but it's an average cold fridge. I'd say about 8 to 9 C above freezing.

Does this make any sense whatsoever? I am a child of the 60s but do not hallucinate. This was ice(if you can call frozen xyz "ice").

You must've threw up on your keyboard last night.

Don't put the carrots on the bottom shelf, the same thing will happen.

DavidS · 21st June 2012, 01:12 PM

Originally Posted by quarky

Yeah.
12 should do it.

You're making it much too complex.
H2O, under pressure, has a lower freezing point. Relieve the pressure? Presto-chango.

To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately).

phunk · 21st June 2012, 01:24 PM

Originally Posted by quarky

Yeah.
12 should do it.

You're making it much too complex.
H2O, under pressure, has a lower freezing point. Relieve the pressure? Presto-chango.

You don't need lower pressure.

Here's the same effect with an unopened bottle. Note that water expands as it freezes, so the pressure in the bottle is actually increasing as it freezes.

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Ziggurat · 21st June 2012, 01:39 PM

Originally Posted by DavidS

To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately).

At least with my soda, "frozen solid" wasn't actually frozen solid. There was a network of ice crystals throughout the whole bottle, but I think it was more like a sponge than a block, judging by the way it subsequently melted. So I suspect this is what happens: the temperature reaches below the freezing point of the bottle if the bottle wasn't under pressure. When pressure is released, it therefore starts freezing, but the freezing process liberates heat, raising the temperature up to the freezing point and halting any further freezing. So only a fraction of the bottle actually freezes, but that fraction is distributed throughout the entire bottle because the freezing process happens faster than heat can travel the length of the bottle. The fact that ice crystals are very anisotropic is probably also important to this process, since it means crystals can extend the length of the bottle before they fill its volume.

quarky · 21st June 2012, 06:47 PM

Originally Posted by DavidS

To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately).

Yes.
The phase change is expensive.
I've observed that phenomena, watching a pool freeze. The crystals pulsate; forming and heating; reforming nearby; until, eventually, an ice cover.

Ziggurat's description is what I've observed with the beer can; its more like a slushy that occurs almost instantly. It expands and makes a mess, yet you can't drink it because the slush is too thick to come out the hole.
Yet, it accommodates some space.

Mike! · 21st June 2012, 07:52 PM

Originally Posted by AvalonXQ

You mean "lowest freezing point".

But, yeah, this exactly. There was ice on the apples because the air was coldest there, and the condensation on the apples can freeze without freezing any of the other solutions / suspensions in the fridge.

No, I think 'highest freezing point' would be correct. If one assumes higher numerical on a scale, the higher the temp it freezes at would happen sooner.

I think.

Foolmewunz · 22nd June 2012, 07:55 AM

Originally Posted by bottsranzee

You must've threw up on your keyboard last night.

(snipped possibly relevant material)

Does anyone have a clue as to what this means?

CosmicDP · 22nd June 2012, 08:02 AM

Originally Posted by Foolmewunz

Does anyone have a clue as to what this means?

20th June 2012, 01:40 PM	#41
quarky Banned Join Date: Oct 2007 Posts: 20,454	Originally Posted by Ziggurat I don't think the effect is because of an inability to nucleate ice crystals - after all, beer and soda aren't particularly pure. I think the effect is primarily due to the pressure dependence of the freezing point: since water expands when it freezes, the freezing point drops when you pressurize it. Which also means that the freezing point rises when you depressurize it. Exactly. Gas law stuff. Flip side of pressure cooking. Glad you said it first, as you have more credibility. The other explanations get a bit too 'precious'.
quarky Banned Join Date: Oct 2007 Posts: 20,454

20th June 2012, 04:34 PM	#42
DavidS Muse Join Date: Dec 2006 Posts: 519	Originally Posted by Ziggurat I don't think the effect is because of an inability to nucleate ice crystals - after all, beer and soda aren't particularly pure. I think the effect is primarily due to the pressure dependence of the freezing point: since water expands when it freezes, the freezing point drops when you pressurize it. Which also means that the freezing point rises when you depressurize it. As noted already (and without actually consulting data tables) I think water's freezing point is too weak a function of pressure for that to make much difference. Off the top of my head, it's 273.15 K at 1 atm and 273.16 K at ~0.006 atm. OTOH, dissolved stuff -- like CO2 -- depresses the freezing temperature exactly the same way antifreeze does in your car's radiator. It's not hard to imagine CO2+water in equilibrium several degrees below the freezing point of more-pure water. I can imagine four mechanisms for sudden liberation of CO2 from solution to induce freezing: - Separation of CO2 into the bubble would freshen the adjacent water, raising its freezing point above the ambient temperature. - The CO2 phase change would consume some latent heat of vaporization, helping to depress or maintain the low temperature. - Forming the bubble surface interface film would consume surface energy (work/area), AKA surface tension (force*length/area -> force/length), also depressing or mantaining temperature. Since surface area increases with the square of the bubble diameter, that can be a big energy drain from the tiny liquid volume around a tiny bubble. - Any ice crystals that form liberate their own latent heat of fusion, but that's partly offset by the energy consumed to create their own phase interfaces. Again, while crystals are tiny that can be a net energy sink. Alas, I can't cite authoritative reference that these control the observed phenomenon. I shall, however, endeavor to acquire my own independent, if merely qualitative observations. A twelve pack should be a good start, right?
DavidS Muse Join Date: Dec 2006 Posts: 519

20th June 2012, 05:26 PM	#43
quarky Banned Join Date: Oct 2007 Posts: 20,454	Yeah. 12 should do it. You're making it much too complex. H2O, under pressure, has a lower freezing point. Relieve the pressure? Presto-chango.
quarky Banned Join Date: Oct 2007 Posts: 20,454

20th June 2012, 06:51 PM	#44
bottsranzee Thinker Join Date: Sep 2011 Posts: 220	Originally Posted by Foolmewunz Not one I have the answer to, but I'm a notoriously lazy bastage and you sciencey guys have this information stored away in your heads. I went to peel my son's apple for his lunch box yesterday morning. Every liquid product in the refrigerator was still liquid, e.g. not frozen. That includes milk, soy milk, coca cola, beer, water and something similar to Red Bull. So the temp in the fridge wasn't going haywire. The apples are in a plastic produce bag in the bottom bins of the fridge. The freezer compartment is at the top and is a separate door (not a combined unit). On the surface of the apples there were ice crystals. Not like little flakes of frost from a bad freezer, but a thin coating of ice. My immediate reaction, as you can see from the above, was that the fridge must've gotten too cold and everything was frozen or freezing over. But it was just this one product - the apples. Thus we get to the puzzle. My fallback solution is that there's some sort of chemical or solution that freezes at a much higher temperature than water and that when the apples sweated (they were in a plastic bag), this chemical or solution was still present in enough strength. Alternately, does an apple exude some sort of fume that might combine with moisture and cold air to freeze at that high a temp? Knowing that someone's going to ask... I tried to replicate the conditions and was hoping to get a picture, but it did not occur this morning when I opened the plastic bag of apples again. Also, I do not have an accurate thermometer handy, but it's an average cold fridge. I'd say about 8 to 9 C above freezing. Does this make any sense whatsoever? I am a child of the 60s but do not hallucinate. This was ice(if you can call frozen xyz "ice"). You must've threw up on your keyboard last night. Don't put the carrots on the bottom shelf, the same thing will happen.
bottsranzee Thinker Join Date: Sep 2011 Posts: 220	__________________ Bottsrgeddon is coming; be ready. bottsr.com

21st June 2012, 01:12 PM	#45
DavidS Muse Join Date: Dec 2006 Posts: 519	Originally Posted by quarky Yeah. 12 should do it. You're making it much too complex. H2O, under pressure, has a lower freezing point. Relieve the pressure? Presto-chango. To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately).
DavidS Muse Join Date: Dec 2006 Posts: 519

21st June 2012, 01:39 PM	#47
Ziggurat Penultimate Amazing Join Date: Jun 2003 Posts: 26,201	Originally Posted by DavidS To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately). At least with my soda, "frozen solid" wasn't actually frozen solid. There was a network of ice crystals throughout the whole bottle, but I think it was more like a sponge than a block, judging by the way it subsequently melted. So I suspect this is what happens: the temperature reaches below the freezing point of the bottle if the bottle wasn't under pressure. When pressure is released, it therefore starts freezing, but the freezing process liberates heat, raising the temperature up to the freezing point and halting any further freezing. So only a fraction of the bottle actually freezes, but that fraction is distributed throughout the entire bottle because the freezing process happens faster than heat can travel the length of the bottle. The fact that ice crystals are very anisotropic is probably also important to this process, since it means crystals can extend the length of the bottle before they fill its volume.
	__________________ "As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law

21st June 2012, 06:47 PM	#48
quarky Banned Join Date: Oct 2007 Posts: 20,454	Originally Posted by DavidS To raise the freezing temperature to allow some ice formation is one thing. But unless something sucks up the latent heat of the phase change, a teeny bit of ice formation will liberate enough heat to stop further freezing in its tracks. Changing one ounce of water from liquid to ice releases enough energy to warm a dozen ounces of water a dozen degrees (approximately). Yes. The phase change is expensive. I've observed that phenomena, watching a pool freeze. The crystals pulsate; forming and heating; reforming nearby; until, eventually, an ice cover. Ziggurat's description is what I've observed with the beer can; its more like a slushy that occurs almost instantly. It expands and makes a mess, yet you can't drink it because the slush is too thick to come out the hole. Yet, it accommodates some space.
quarky Banned Join Date: Oct 2007 Posts: 20,454

21st June 2012, 07:52 PM	#49
Mike! Official Ponylandistanian National Treasure. Respect it! Join Date: May 2010 Location: Ponylandistan! Where the bacon grows on trees! Can it get any better than that? I submit it can not! Posts: 10,257	Originally Posted by AvalonXQ You mean "lowest freezing point". But, yeah, this exactly. There was ice on the apples because the air was coldest there, and the condensation on the apples can freeze without freezing any of the other solutions / suspensions in the fridge. No, I think 'highest freezing point' would be correct. If one assumes higher numerical on a scale, the higher the temp it freezes at would happen sooner. I think.
	__________________ "Never judge a man until you’ve walked a mile in his shoes... Because then it won't really matter, you’ll be a mile away and have his shoes."

22nd June 2012, 07:55 AM	#50
Foolmewunz Grammar Resistance Leader Join Date: Aug 2006 Location: Pattaya, Thailand Posts: 20,520	Originally Posted by bottsranzee You must've threw up on your keyboard last night. (snipped possibly relevant material) Does anyone have a clue as to what this means?
	__________________ Ha! Foolmewunz has just been added to the list of people who aren't complete idiots. Hokulele Don't you wish someone had slapped baby Hitler really really hard? [i] Dr. Buzzo 02/13 [i]

22nd June 2012, 08:02 AM	#51
CosmicDP Thinker Join Date: Sep 2011 Location: Holiday Inn Express Posts: 165	Originally Posted by Foolmewunz Does anyone have a clue as to what this means?