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  • OT freezing water

    Read in the news today that scientists have determined the lowest temperature that water can reach before it MUST freeze- -48C. Above that temperature it takes a seed of some kind to start the first crystal. Ordinary tap water will freeze at 0 degrees because there are always impurities present.

    I thought it was interesting that you can cool pure water to below 0, then cause it to begin turning to ice by rapping on the container. In a minute or less, the entire bottle converts from liquid water to ice.

    At -48, you'd then expect the process to be much quicker- perhaps so quick that it acts like an explosion. I don't recall seeing this, but in some videos I've watched on this topic, the container of water turns to ice- but does it expand the same 10 or 11% that it normally would as the liquid water turns to ice?

    Water sure does have some interesting properties, aside from keeping us alive.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Imagine the implications if water didn't increase in volume when it freezes.
    I just need one more tool,just one!

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    • #3
      Originally posted by wierdscience
      Imagine the implications if water didn't increase in volume when it freezes.

      All those subs banging into ice bergs stooging around hundreds of metres below the surface....

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      • #4
        Hm. Water's latent heat of freeezing leads to some interesting questions if it freezes at -48. Is the resultant ice warmer or colder than the water from which it freezes in this experiment? WHere does the heat go?
        Last edited by Forrest Addy; 11-26-2011, 04:29 AM.

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        • #5
          Originally posted by Forrest Addy
          Hm. Water's latent heat of freeezing leads to some interesting questions if it freezes at -48. Is the resultant ice warmer or colder than the water from which it freezes in this experiment? WHere does the heat go?
          A question worthy of a true scientist. :-)
          ...lew...

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          • #6
            I've left bottled water in the car before, and they were liquid, until you opened the cap, then they freeze. I always thought it was due to there not being sufficient room for the water to expand when it's sealed. Never really put much though into it, just always get pissed at trying to drink from a slush bottle.

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            • #7
              Hm. Water's latent heat of freeezing leads to some interesting questions if it freezes at -48. Is the resultant ice warmer or colder than the water from which it freezes in this experiment? WHere does the heat go?
              It's already gone. Water is a very anomalous substance. It "breaks" all the rules. I would have to look it up but when it freezes at that temperature it probably forms a different ice than it does normally. There are at least 10 types of ice that can form depending on temperature and pressure. Water can be supercooled to much below -48 under some conditions.

              See here for the many anomalous properties of water:

              http://www.lsbu.ac.uk/water/anmlies.html
              Last edited by Evan; 11-26-2011, 11:24 AM.
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              • #8
                Originally posted by darryl
                Read in the news today that scientists have determined the lowest temperature that water can reach before it MUST freeze- -48C. Above that temperature it takes a seed of some kind to start the first crystal. Ordinary tap water will freeze at 0 degrees because there are always impurities present.

                I thought it was interesting that you can cool pure water to below 0, then cause it to begin turning to ice by rapping on the container. In a minute or less, the entire bottle converts from liquid water to ice.
                Soooo, in some perfect world you could fill your perfect engine with pure water and it would be good to -48c. However, once you start it and the cylinders start firing and creating vibration it would turn to ice in 1 minute and crack the block.

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                • #9
                  Originally posted by The Artful Bodger
                  All those subs banging into ice bergs stooging around hundreds of metres below the surface....
                  No fish in any northern lakes or oceans for that matter is a bit more of an implication,almost as bad as stuck cable releases on Helicopters
                  I just need one more tool,just one!

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                  • #10
                    If water acted like it "should" there would be no life on Earth, most likely. But then, if it acted any other way the rules of the universe would be entirely different.
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                    • #11
                      Originally posted by Evan
                      It's already gone. Water is a very anomalous substance. It "breaks" all the rules. I would have to look it up but when it freezes at that temperature it probably forms a different ice than it does normally. There are at least 10 types of ice that can form depending on temperature and pressure. Water can be supercooled to much below -48 under some conditions.

                      See here for the many anomalous properties of water:

                      http://www.lsbu.ac.uk/water/anmlies.html
                      Now wait a minute, your assertion that water can be supercooled far below -48 (even as qualified) is in direct contrast to the opening statement of this thread.

                      What are these different types of ice? Strawberry, lemon-lime, grape,....?

                      I liked his footnote at the bottom of that "Anomalous" link above:
                      "....Whether or not the properties of water are seen to be anomalous depends upon the materials used in the comparison and the interpretation of the term 'anomalous'. For example, it could well be argued that water possesses exactly those properties that one might deduce from its structure ..."

                      I would say so, unless one has flaws in one's deductive processes.
                      Or maybe mother nature has made a mistake here.
                      Lynn (Huntsville, AL)

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                      • #12
                        It has been a while since I read up on this and a quick check shows they have managed to produce a few more types of ice since I last studied this.

                        There are 16 possible kinds of water ice, each with a different crystal structure and density. They form at various temperatures and pressures and some have very different properties than Ice I. Except at very low temperatures it requires at least 2000 bar to form Ice II through Ice XV. There are actually 2 types of Ice I. Ice Ih (h for hexagonal) is the "normal ice". Ice 15 is the last according to the theoretical properties considered possible. Most of the ices are denser than liquid water.

                        With sufficient pressure liquid water can be supercooled to something like -91, IIRC. Under very special conditions it can even be glassified. With the exception of the supercooled state mentioned in the original post all the other forms are unstable in the range of environmental conditions found on Earth. The supercooled state is considered "metastable" as it will revert to Ice I if disturbed.

                        Of the many anomalous properties one in particular is very important. The viscosity of water changes dramatically with temperature even though it isn't obvious. Between +4 C and boiling water decreases viscosity by about 4 times which is one reason hot water cleans clothing much better than cold water.
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                        • #13
                          I believe (and don't quote me on this), that in food processing plants using flash-freezing technology they very quickly chill the food to a temperature that will give them Ic (1, cubic) as compared to Ih (1, hexagonal). Apparently the Ic phase causes less damage to the cells of the food being frozen, so it is 'fresher' and tastes better when it is thawed.

                          Takes some mighty big equipment to get down cold enough (sub -50C).

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                          • #14
                            Any help?

                            I saw this item in a science item in our national broad-casting network (ABC) in Australia recently.

                            Any help?

                            http://www.abc.net.au/science/articl...24/3374497.htm

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                            • #15
                              Interesting. This result is applicable to standard pressure only though. I also have slight issues in that the result was not derived experimentally. Instead it was obtained by using a computer model. Models are very valuable in describing physical phenomena but they tend to have problems at boundary conditions. This is an example of a boundary condition.

                              Also, I have an issue with the explanation.

                              Supercooled water has been studied experimentally to minus 41.11° Celsius. That's near its homogenous nucleation temperature — the lowest temperature at which ice crystallisation rates can be measured as water freezes.

                              But the actual mechanism of ice crystallisation remained a mystery because below this temperature, ice crystallises too fast for any property of the remaining liquid to be measured.

                              To overcome this problem, Molinero and Moore developed new computer models to simulate pure water freezing.

                              http://www.sciencedaily.com/releases...0511173855.htm

                              They found that at minus 48° Celsius, well below the homogenous nucleation temperature, the molecular structure of water physically changes, forming tetrahedron shapes in which each water molecule loosely bonds to four adjacent molecules.

                              "The water is transforming to something else, and this something else is very close to ice," says Molinero.

                              "This intermediate ice has a structure between the full structure of ice and the structure of the liquid."

                              "The findings suggest this structural change from liquid to ice explains the mystery of what determines the temperature at which water is going to freeze," she says.
                              This is where the boundary condition issue comes into play. Liquid water doesn't have a structure and therefore cannot be precisely modeled.

                              I also don't think the statement that the ice forms too fast to measure is accurate. By using attosecond laser pulses it is possible to measure exceedingly rapid phenomena.

                              ScienceDaily (May 11, 2010) — Lasers can now generate light pulses down to 100 attoseconds thereby enabling real-time measurements on ultrashort time scales that are inaccessible by any other methods.
                              http://www.sciencedaily.com/releases...0511173855.htm

                              100 attoseconds is about the amount of time it takes light to travel 1/10 of a micron. Further, the pulse position uncertainty is only 12 attoseconds.

                              The new method allowed to push this limitation down to 12 attoseconds (1.2 x 10-17 s, 1/200 of the wavelength), which surpasses the atomic unit of time (24 attoseconds) by a factor of two. As the atomic unit of time marks the fastest possible time scale of processes in the outer shells of an atom, the new stabilization method will enable significant progress in the research on the fastest processes in nature.
                              It is unlikely that the freezing process comes anywhere close to this timescale since it requires considerable movement of the water molecules to align from a chaotic arrangement to a crystal structure.
                              Last edited by Evan; 11-26-2011, 08:58 PM.
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