Battery Junction - Olight
Page 1 of 2 12 LastLast
Results 1 to 30 of 34

Thread: Water needs air to freeze?

  1. #1
    Flashaholic*
    Join Date
    Sep 2004
    Posts
    2,959

    Default Water needs air to freeze?

    I have my freezer full of deer park water bottles and use one for my neck for mild pain relief. ANyway, I unscrewed the lid to let some air out as the bottle looked like it was about to explode. Later on I accidently unscrewed the lid with it under a shoulder and some air and water came out. I screwed the lid back on right and pulled it out.

    After being in the freezer for 2 days, it was still liquid and the bottle looked crushed. I unscrewed the top a bit to let in some air and it seemed to instantly freeze. Later on I checked on it and it was rock solid, but the water or ice was clearer than the other bottles.

    Just wondering.......

  2. #2

    Default Re: Water needs air to freeze?

    Water freezes at 0C or 32F at normal atmospheric pressure. It doesn't require air to freeze, but the atmospheric pressure plays a physical role in the change of state. Freezing point is higher under higher pressures, and lower under lower pressures.

    The crushed look from your bottle in the freezer was due to the air in the bottle contracting at the low temperatures, creating an even greater vacuum. The water too contracts at lower temperatures, until it reaches the freezing point and then expands. The low pressure in the bottle may have lowered the freezing point of the water to even lower than the temperature of your freezer. When you opened the cap, the air pressure equalized with the atmospheric pressure and restored the freezing point to 32 degrees. Considering the temperature of the water, it should freeze nearly instantly.

    Incidentally, if you were keenly aware of everything occurring, you would noticed that the bottle temperature raised just a bit while it froze. That's because the water, when it changed to a solid state, gave off 80 calories of heat for every gram of water in it.
    <font color="red">

    Edit: *Warning* consider the remarks regarding pressure in this posting unsupported and unreliable. Actually, consider the comments as backward. For the sake of continuity with the follow-up commentary and worthwhile opposing viewpoints, I've left the comments intact.
    </font>

  3. #3
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    Water, whether freezing or boiling, usually needs some sort of "seed" to start the process.

    If you have filtered water and a smooth container, you can have either super heated liquid (above boiling) or super cooled liquid (below freezing).

    There are other chemicals that are more prone to this than water (remember in chemistry class you had to have a glass rod or marbles in the bottom of a beaker before "boiling" a liquid.

    With water, it is rare to see it happen--I have seen it a few times with bottled water in a home freezer (it is "cool" to watch a bottle of water freeze solid in just a few seconds after you give it a shake), or in a microwave if you have ever boiled some hot water in a glass container only to hear a "pop" and find much of the water blown out of the cup.

    The point at which the phase change is initiated is called the "nucleation site"... (IIRC).

    Regarding the bottle looking crushed--if you have been freezing and thawing the same bottle--the plastic will be stretched when the water freezes and when the water thaws (or is super cooled) the volume of the water will be roughly 7% (IIRC) less than the ice was--forming a partial vacuum in the now oversized bottle.

    -Bill

  4. #4
    Flashaholic*
    Join Date
    Apr 2002
    Location
    Boise, ID
    Posts
    2,639

    Default Re: Water needs air to freeze?

    I've supercooled water in a shot glass before. I used a peltier to cool the water down, it got to about -5C, then by tapping the glass with the thermocouple probe I had in the glass, I was able to form a nucleation site, causing instant solidification of much of the water. The neat thing was, that the remaining liquid water ended up at about 3 or 4C immediatley afterwords. The solidifying water dumped the excess energy from the phase change into the surrounding water, warming it up.

  5. #5
    *Flashaholic* greenLED's Avatar
    Join Date
    Mar 2004
    Location
    La Tiquicia
    Posts
    13,244

    Default Re: Water needs air to freeze?

    There's ice in space. Is it pure H2O?

  6. #6
    Flashaholic* Sub_Umbra's Avatar
    Join Date
    Mar 2004
    Location
    la bonne vie en Amérique
    Posts
    4,748

    Default Re: Water needs air to freeze?

    [ QUOTE ]

    Water freezes at 0C or 32F at normal atmospheric pressure. It doesn't require air to freeze, but the atmospheric pressure plays a physical role in the change of state. Freezing point is higher under higher pressures, and lower under lower pressures.

    [/ QUOTE ]

    Emphasis mine.

    Wouldn't the opposite be true? Have you ever placed a warm soda (mostly water) into the freezer after bringing it home from the store? If you leave it in the freezer just a little too long to chill it, it looks just fine (still liquid) as long as the cap still is on (under higher pressure than one atmosphere). When the cap is removed and the contents drop to a lower pressure it slushes up or freezes up instantly.

    That would indicate that greater atmospheric pressure LOWERS the freezing point of water.

  7. #7
    Moderator js's Avatar
    Join Date
    Aug 2003
    Location
    Upstate New York
    Posts
    5,683

    Default Re: Water needs air to freeze?

    I'm pretty sure that the supercooling phenomenon can account for some, all, or more than all, of the energy of fusion (80cal/g), so that it is possible for the water to solidify very quickly and NOT pull ANY heat from its' surrounding, or even end up at less than 0 C. Otherwise, you would end up with some contradictions, thermodynamically speaking, because it takes energy to supercool a liquid. i.e. you must remove more heat from it than you would need to merely to bring it to the freezing point.

  8. #8
    Flashaholic*
    Join Date
    Dec 2002
    Location
    Taxachusetts, USA
    Posts
    1,036

    Default Re: Water needs air to freeze?

    In the phase diagram here at Encarta you can see that for a given temp (say, just below zero C) increasing the pressure will return the frozen phase to liquid, and lowering the pressure will return it back to solid.

    So... (within that range below the triple-point on the diagram) LOWER =&gt; solid, HIGHER =&gt; liquid
    And... freezing point occurs at a LOWER temp under higher pressure, and HIGHER under lower pressure.

  9. #9
    Moderator js's Avatar
    Join Date
    Aug 2003
    Location
    Upstate New York
    Posts
    5,683

    Default Re: Water needs air to freeze?

    Sub,

    Yeah, I was just mentally thinking through that same thing, and wishing that I had my thermodynamic text book from college. Then I realized I DO HAVE MY THERMO BOOK. I was psyched! Ran to my office, opened it up, and checked.

    Yes. For a pure substance that expands upon freezing, the solid-liquid interface line has a negative slope on the pressure vs. temperature line. So yes, at higher pressures, the freezing temperature is lower.

    However, it's just a bit more involved than that, because that graph is assuming that the volume can be whatever it needs to be. But if you restrict the volume in one or more dimensions, that changes things, I think (but I'm not sure.) In other words I think that if you prevent water from being able to expand (which takes ENORMOUS FORCE) that you will supercool it.

    But certainly, if you exert pressure on a volume of water via the air, for example, then yes, water freezes at a slightly higher temperature in Denver, than in Boston.

    Also, as you point out, keeping the temperature fixed, it is possible to go from high pressure to low, and cross the solid-liquid line, thus causing the soda to turn to slush.

    And then there's the triple point, but I remember that that thing gave me a head ache when I took thermo, so I'll let that be. But it's a neato idea. There is only one point on the pressure-temperature graph where solid, liquid, and gaseous H2O can all co-exist. But, it's specific volume would depend on the exact ratios of those things. i.e. it's possible to have varying amounts of ice, water and gas for the same initial mass of water.

  10. #10
    Moderator js's Avatar
    Join Date
    Aug 2003
    Location
    Upstate New York
    Posts
    5,683

    Default Re: Water needs air to freeze?

    [ QUOTE ]
    binky said:
    In the &lt;url="http://encarta.msn.com/media_461541579/Phase_Diagram_for_Water.html"&gt;phase diagram here at Encarta&lt;/url&gt; you can see that for a given temp (say, just below zero C) increasing the pressure will return the frozen phase to liquid, and lowering the pressure will return it back to solid.

    So... (within that range below the triple-point on the diagram) LOWER =&gt; solid, HIGHER =&gt; liquid
    And... freezing point occurs at a LOWER temp under higher pressure, and HIGHER under lower pressure.

    [/ QUOTE ]

    You MUST be ABOVE the triple-point to be at the solid-liquid phase line.

  11. #11
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    Without referring to a my 30 year old chemistry book... The amount of heat released taking water from 100C to 0C is approximately the same amount as the energy released at taking water from liquid to solid at 0C.

    So, what Evan observed is really more to the point--when I saw the water "flash freeze"--the ice was probably forming down the walls of the bottle and left a core of unfrozen water--that had been warmed by the act of crystallization.

    I don't believe that there is any substantial energy difference between cooling water from 5C to 0C as there is super cooling water from 0C to -5C... The massive energy release is the act of crystallization itself.

    Regarding the change in water freezing point would require larger changes in pressure I believe than the few PSI or tens of PSI possible in a water bottle.

    Here is a quick link on water freezing...

    Water Freezing Properties under High Pressure

    To drop the freezing point of water to ~-22C, you would need to pressurize it to approximately 2.7kBars (roughly 40,000 PSI)... More info on the link.

    I have to go now... Bye!

    -Bill

  12. #12
    Flashaholic*
    Join Date
    Dec 2002
    Location
    Taxachusetts, USA
    Posts
    1,036

    Default Re: Water needs air to freeze?

    [ QUOTE ]
    js said:
    [ QUOTE ]
    binky said:
    In the phase diagram here at Encarta you can see that for a given temp (say, just below zero C) increasing the pressure will return the frozen phase to liquid, and lowering the pressure will return it back to solid.

    So... (within that range below the triple-point on the diagram) LOWER =&gt; solid, HIGHER =&gt; liquid
    And... freezing point occurs at a LOWER temp under higher pressure, and HIGHER under lower pressure.

    [/ QUOTE ]

    You MUST be ABOVE the triple-point to be at the solid-liquid phase line.

    [/ QUOTE ]

    I was actually referring to temp there. Really. What I meant was that if you choose some given temp in that range below the triple-point, and you travel LOWER &amp; HIGHER in pressure... etc.
    That's honestly what I meant. You gotta be BELOW the triple-point on temp to get any solidification. We're saying the same thing. Sorry for the mixup.

  13. #13
    Flashaholic* Sub_Umbra's Avatar
    Join Date
    Mar 2004
    Location
    la bonne vie en Amérique
    Posts
    4,748

    Default Re: Water needs air to freeze?

    Jim,

    Thanks for the explanation. After my first post I Googled around a bit and became really confused. Funny you should mention a headache. This is way too much for me. I'm really just the guy trying to get his Diet DR Pepper cold without having the slush come out when I open it.

    Sub

  14. #14
    Administratior
    Brock's Avatar
    Join Date
    Aug 2000
    Location
    Green Bay, WI USA
    Posts
    6,345

    Default Re: Water needs air to freeze?

    Yup, sea water at say 5000 feet can be well below -10F and stay liquid becasue of the pressure.

  15. #15
    Moderator js's Avatar
    Join Date
    Aug 2003
    Location
    Upstate New York
    Posts
    5,683

    Default Re: Water needs air to freeze?

    Brock,

    You mean, 5000 feet below the surface, right? Wow. Kewl. That's wild. Neat!

  16. #16

    Default Re: Water needs air to freeze?

    I recall reading that in one of the first deep sea labs, one of the researchers brewed some instant coffee (they were under pressure; above 1 atm) and proceeded to burn his mouth and throat rather severly. The water was considerably hotter than normal when it came to a boil. [img]/ubbthreads/images/graemlins/icon15.gif[/img]

  17. #17
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    Brock, I am confused... You said that sea water can be at -5ºF at 5,000’ because of the temperature… I don’t think so. It could only be at this state because of super cooling of the sea water, not because of the salt content or the lower atmospheric pressure.

    Sea water begins to freeze about -2ºC (~29ºF). An Eutectic (sodium chloride) Brine solution freezes at -6ºF (-34ºC). And from the table I posted earlier freezing point of fresh water decreases with increased pressure "by about 0.55ºC per 80 atmospheres of pressure down to about -22ºC at 2,700 atmospheres of pressure"... And you can super cool fresh water down to about -42ºC (about -43ºF). And even a NaCl brine solution—if I read the research correctly it shows that you can get a super cooled liquid down to the -45C range.

    The links below correspond to the point, in order, made above:

    Properties of Sea Water
    Salt Brine for Fishing Industry
    High Pressure Cryonics
    Amorphous Ice and Glassy Water
    Super Cooled Brine Solution (pdf)

    And in your example you are lessening the pressure by less than 0.25 Bar (a Bar is 1 atmosphere which is roughly 14.7 PSI at sea level--IIRC)--which, if anything should cause the ice to form at a, very slightly, warmer temperature at 5,000 feet. But absent super cooling, sea water should begin freezing around 29ºF and probably freeze solid by around -6ºF (assuming the brine becomes more and more concentrated—if that is even a possibility).

    Am I missing something?

    -Bill

  18. #18
    *Flashaholic* greenLED's Avatar
    Join Date
    Mar 2004
    Location
    La Tiquicia
    Posts
    13,244

    Default Re: Water needs air to freeze?

    so... ice in space, anyone?

  19. #19
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    "pure water ice in space"... Well you can place an ice cube in space from a space ship--but it will probably evaporate within a few minutes to a few hours (to sublime is to change from solid to gaseous state without melting) if it is anywhere near earth/solar system.

    Will you find "pure water" in space? Probably not pure in the sense you could drink it.

    There are instances of, what is believed to be water ice,
    <ul type="square">[*] at the poles of the Moon in deep craters protected from the sun,[*]possibly on Mars and moons around outer planets with atmospheres,[*]and comets are believed to be "dirty snowballs" and the trail you see is the solar wind blowing the melting gases from the head of the comet as it comes closer and closer to the sun.[/list]

    Is this kind of what you were asking Green?

    -Bill

  20. #20
    Flashaholic* mattheww50's Avatar
    Join Date
    Jun 2003
    Location
    SW Pennsylvania
    Posts
    823

    Default Re: Water needs air to freeze?

    Actually the most likely explanation is one long understood.
    Presence of any dissolved substance in water depresses the freezing point, about 2 degrees per mole of solute/liter. However some molecules disassociate in water, so for instance 1 mole of salt (NaCl) will depress the freezing point more than 2 degrees because you end up with roughly a mole of sodium and roughly 1 mole of Chlorine.


    Also keep in mind that while the solubility of solids decr eases with decreasing water temperature, the solubility of gases INCREASES. There is usually considerable air dissolved in tape water (by design). The reason the ice cubes you make are not clear, is the air is forced out of solution as it freezes. If you want clear ice cubes, boil the water first to drive the dissolved air out, or thaw and refreeze the ice.

    Many is the can of soda I have taken out of the freeze, and watched it promptly freeze after I opened it.
    opening it allowed the gas (carbon dioxide to come out of solution), so it was suddenly below the freezing point, and promptly turned to slush..

  21. #21
    Flashaholic*
    Join Date
    Dec 2002
    Location
    Taxachusetts, USA
    Posts
    1,036

    Default Re: Water needs air to freeze?

    Y'know, there are a bunch of great comments on some things that are going on when you see that soda slush up, and I'm having fun laughing at myself for having forgotten so much chem/thermo.

    Here's another effect involved, from the dynamic rather than just static thermo perspective:
    It's not just the lower pressure or the solution/dissolution that's going on. When you open the bottle you're letting out the gas. That lowers the enthalpy of the system (if you draw your border at the bottle) meaning the inside of the bottle gets colder because it's losing energy. The same effect is seen when you let CO2 out of one of those little cylinders and it gets so cold that it frosts up, just from letting the gas out.

    That's soda. Doesn't have anything to do with cobb's initial water bottle question.

  22. #22
    *Flashaholic* greenLED's Avatar
    Join Date
    Mar 2004
    Location
    La Tiquicia
    Posts
    13,244

    Default Re: Water needs air to freeze?

    Thanks, Bill! It was the "dirty snowball" comet thingy that was in my mind.

  23. #23

    Default Re: Water needs air to freeze?

    One night on a backpacking trip it dipped under freezing - possibly down to ~20F. We had bought some inexpensive bottled water in 2L bottles for the trip.

    The morning after the freeze, I was about to open one bottle when I noticed the water inside was kind of "hazy." It was kind of like lookingg through a perfectly uniform fog bank. The contents were still liquid, so I didn't give it much notice. When I opened the bottle, there was a loud hiss of escaping air and the entire thing flash-froze into a flawless block of ice.

    The compressed air represented the energy from the phase change being released - it also allowed the liquid &gt;&gt; solid expansion to occur.

  24. #24
    Administratior
    Brock's Avatar
    Join Date
    Aug 2000
    Location
    Green Bay, WI USA
    Posts
    6,345

    Default Re: Water needs air to freeze?

    Woops, since I am a diver I assume 5000' is 5000 feet down, not up, sorry for the confusion guys.

    Bill I am also confused I thought sea water froze at 0F and thats where oF came from?

  25. #25

    Default Re: Water needs air to freeze?

    [ QUOTE ]
    Brock said:
    Woops, since I am a diver I assume 5000' is 5000 feet down, not up, sorry for the confusion guys.

    Bill I am also confused I thought sea water froze at 0F and thats where oF came from?

    [/ QUOTE ]

    Using the metric system, reasonably pure water at 1 atmosphere (sea level, 14.7 PSI.), freezes at 0 degress Celsius (or Centigrade); which is equivalent to 32 degrees Farenheit.

    That's probably the 'zero degrees' you are thinking of.

  26. #26
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    And I flew light planes and assumed you were talking about Denver... who knew? I did wonder why sea water and Denver were together in the argument…

    Anyway... Fahrenheit temperature scale

    [ QUOTE ]
    The Fahrenheit temperature scale became popular through its use on the first reliable, commercially-available, mercury-in-glass thermometers. Daniel Gabriel Fahrenheit manufactured such thermometers in Amsterdam from about 1717 until his death in 1736. The scale we know of as the Fahrenheit scale was the last of three scales he used.

    As the zero point on his scale Fahrenheit chose the temperature of a bath of ice melting in a solution of common salt, a standard 18th century way of getting a low temperature in the laboratory (and in the kitchen, as in an old-fashioned ice cream churn). He set 32 degrees as the temperature of ice melting in water. For a consistent, reproducible high point he chose the temperature of the blood of a healthy person (his wife), which he measured in the armpit and called 96 degrees.

    [/ QUOTE ]

    And you can get brine down to -5F or so... Pretty close to 0F. From what I remembered, 0F had nothing to do with sea water but was an ice/brine solution.

    I have also read this explanation before:

    Fahrenheit scale, why is 32 freezing and 212 boiling?

    [ QUOTE ]
    Daniel Gabriel Fahrenheit (1686-1736) was a German instrument maker who invented the first practical mercury thermometer. Casting about for a suitable scale for his device, he visited the Danish astronomer Ole Romer, who had devised a system of his own.

    As it turned out, it was a case of the blind leading the blind.

    Romer had decided that the boiling point of water should be 60 degrees. This at least had the strength of numerological tradition behind it (60 minutes in an hour, right?).

    But zero was totally arbitrary, the main consideration apparently being that it should be colder than it ever got in Denmark. (Romer didn't like using negative numbers in his weather logbook.)

    In addition to the boiling point of water, the landmarks on Romer's scale were the freezing point of water, 7-1/2 degrees, and body temperature, 22-1/2 degrees.

    D.G., simple soul that he was, thought this cockeyed system was the soul of elegance. He made one useful change: to get rid of the fractions, he multiplied Romer's degrees by 4, giving him 30 for the freezing point and 90 for body temperature.

    Then, for reasons nobody has ever been able to fathom, he multiplied all the numbers by 16/15, making 32 freezing and 96 body temperature. Boiling point for the time being he ignored altogether.

    By and by Fahrenheit got ready to present his scale to London's Royal Society, the scientific big leagues of the day.

    It dawned on him that it was going to look a little strange having the zero on his scale just sort of hanging off the end, so to speak. So he cooked up the explanation that zero was the temperature of a mix of ice, water, and ammonium chloride.

    [/ QUOTE ]

    So take your pick (I tend towards the second link—with working with too much mercury on the side—older thermometers primarily used mercury for the indicator).

    Going under the ocean 5,000' is roughly 150 Atmospheres (~2,200 PSI)--and from the earlier link, this would decrease the temperature water ice would form by about -1C (80 ATMs per -0.55C).

    The boiling point of water is much more affected by pressure than the freezing point. And, with super cooling (and heating) you can get weird effects that kind of blur what the "freezing" and "boiling" of water is...

    -Bill

  27. #27
    Administratior
    Brock's Avatar
    Join Date
    Aug 2000
    Location
    Green Bay, WI USA
    Posts
    6,345

    Default Re: Water needs air to freeze?

    ahhhh now that doesn't clear it up at all [img]/ubbthreads/images/graemlins/wink.gif[/img] Talk about goofey. Anyway what temp does typical sea water freeze then, boy are we off track [img]/ubbthreads/images/graemlins/smile.gif[/img]

  28. #28
    Flashaholic*
    Join Date
    Jun 2003
    Location
    SF Bay Area
    Posts
    2,090

    Default Re: Water needs air to freeze?

    Brock,

    Open ocean sea water begins to freeze around -4C to 28.5F (various sources).

    Now for something completely different... Did you know that there are some species of sea life that have "anti freeze" in their blood that allow them to live under sea ice down to 27.1F?

    What temperature does Sea Water Freeze?

  29. #29
    Flashaholic* asdalton's Avatar
    Join Date
    Dec 2002
    Location
    Northeast Oklahoma
    Posts
    1,708

    Default Re: Water needs air to freeze?

    binky,

    The reason that CO2 regulators get cold is due to a more subtle phenomenon called the Joule-Thompson effect. The temperature of CO2 drops sharply when its pressure is reduced under constant enthalpy, which is precisely the conditions that the gas experiences when being throttled through a regulator or other tight constriction.

    The Joule-Thompson effect for air is pretty weak, because air near atmospheric pressure behaves much more closely like an ideal gas than high-pressure CO2 does. Under ideal gas conditions, the Joule-Thompson effect disappears.

  30. #30
    Flashaholic*
    Join Date
    Sep 2004
    Posts
    2,959

    Default Re: Water needs air to freeze?

    Wow, I had no idea this would take off like this. Much like the guy who went hiking said, I just unscrewed the lid of the bottle that the sides were sucked in and it froze instantly. I was concerned my freezer wasnt working right, but another bottle was frozen completely.

    You guys sound like a smart bunch to hang out with.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •