News24

Supercooled water riddle is solved

2011-11-24 08:09

Paris - At what temperature does water have to freeze?

The answer: Not necessarily at 0°C.

Water can exist in liquid form well below this threshold, notably in a so-called "supercooled" state that is well into the minus zone.

The reason: if you want to form ice from liquid water, you need a "seed" of ice from the liquid - a crystal that becomes the nucleus around which other crystals form.

But in very pure water, which has no contaminants or particles around which the critical nucleus can form, this can be difficult to achieve because of the unusual thermodynamics of H20.

Until now, supercooled water has been measured right down to around -41°C, although scientists have long suspected that the temperature at which it unconditionally has to freeze is somewhat lower.

They have been unable to find out for sure because ice crystallises so fast at this temperature that it is impossible to measure accurately the properties of the remaining liquid.

Chemists Valeria Molinero and Emily Moore at the University of Utah used computer modelling to simulate the behaviour of supercooled water at the microscopic level.

Their programme mimicked what would happen when 32 768 water molecules were cooled, factoring in the heat capacity of water, its density and compressibility.

After thousands of computer hours, the answer came back.

The temperature at which water absolutely must freeze, no questions asked, is -48°C.

When water approaches this temperature, it becomes less dense and becomes easier to compress and its structure changes.

As a result, each molecule links up loosely with four others to form tetrahedron, or pyramid-like, shapes.

The investigators describe this as an "intermediate ice" that is halfway between the structure of the liquid and halfway between the full structure of ice.

The research, published on Wednesday in the British journal Nature, is more than an exercise in scientific curiosity.

Atmospheric scientists delving into global warming need to know temperatures and rates at which water freezes and crystallises into ice. Water as chill as -40°C has been found in clouds.

"You need that to predict how much water in the atmosphere is in the liquid state or crystal state," Molinero said. "This is important for predictions of global climate."

Comments
  • TheSlip - 2011-11-24 08:24

    "Scientists have had a chilling dilemma; what is the temperature that does water has to freeze, no matter what." -- WHAT?

      herculesjansenvanvuuren - 2011-11-24 08:26

      I was just about to make the exact same comment. What has does happened to your spell check and editing News 24,does have what?

      HenningBrazer - 2011-11-24 08:28

      HAHA! Same here! The can definitely censor that sort of writing. Or is it "Can has to censor?"

      Barefoot - 2011-11-24 08:41

      theslip of the the keyboard scientists have have a typing dilemma, what does the way man has to type no matter . . .WHAT?

      TheSlip - 2011-11-24 08:43

      Like my friend's T-shirt says: Every time they "can has", God kills a lolcat.

      Deon - 2011-11-24 09:53

      Listen water, it is time to freeze.

      TheSlip - 2011-11-24 10:30

      @barefoot... I don't even . . .

      Kala - 2011-11-24 11:02

      Freeze!! This is a stick up!!!

      Squeegee - 2011-11-24 12:57

      The point Kala is: stick, this is s freeze up.

      Grim - 2011-11-24 13:03

      yh come on news 24 what’s going on "Atmospheric scientists delving into global warming need to know temperatures and rates at which water freezes and crystallises into ice. Water as chill as -40°C has been found in clouds." Water as chill as...? Surely it’s cold as..? Thought i was taught in school to proof read things.

  • Luke - 2011-11-24 08:27

    mmmm Super Colled water in my whiskey...

      Barefoot - 2011-11-24 08:44

      Next we'll be having super coiled water, what happened to your spell check this morning people? "colled"?

      RatexZa - 2011-11-24 08:47

      Would freeze on contact, with your Bells, or your mouth. Wouldn't try that.

      herculesjansenvanvuuren - 2011-11-24 08:49

      @barefoot. Have have you seen your mistakes has made as well?

      Grim - 2011-11-24 13:05

      why does south africa have a thing for whiskey or whisky..? why not brandy or something purer like vodka. why not just an orange juice?

      Zion - 2011-11-24 13:42

      I like mine dry and on the rocks

      Kala - 2011-11-24 16:29

      @TheHerc - And a couple of mistakes made by yourself.

  • koo.doyle - 2011-11-24 08:37

    The brief as it appears on the front page: "Scientists have had a chilling dilemma; what is the temperature that does water has to freeze, no matter what." Seriously @ News24 editors, hang your heads in shame. Absolutely shocking.

  • Chumscrubber1 - 2011-11-24 08:44

    Gobbledegook!

  • herculesjansenvanvuuren - 2011-11-24 08:45

    Yoda, please to be stopping writing contributorily for News 24, please can has.

      Francois Roux - 2011-11-24 10:10

      ogm that LOL me made...ahahah

  • Tennille - 2011-11-24 08:52

    BWAHAHAHA, I only opened the article because I has had no idea what the headline is mean on the home page.

  • William - 2011-11-24 09:03

    Seems we can like to go back into history when problems were like to be solved by discussing them...

  • Paul - 2011-11-24 09:09

    OK, with the editing sorted, this is a profound discovery. We have long since known that distilled water does not 'boil', and this pure water does not 'freeze' in the true sense. At -48 deg C, all water will freeze by (hither to) an unclear process. One of my professor friend's freezers runs at -80 deg C (nominal) to store bacteria in a distilled solution, and, being 'impure', freezes at just below 0 deg C. I'll get some chemically 'clean' water and try this dicovery out with temp sensors etc. See if I can make super-cooled water for Luke's whiskey. Liquid Nitrogen replacement?

  • karen.vdnest - 2011-11-24 09:18

    Do you want to perhaps try re writing that first sentence?? It makes no freakin sense!!!!!

  • Lettie - 2011-11-24 09:19

    Aagtog! 'n Goeie begrip het 'n halwe woord nodig.

      herculesjansenvanvuuren - 2011-11-24 10:12

      Maar 'n halwe sin maak dat die hele deel onduidelik is.

      Jaco - 2011-11-24 10:21

      'n halwe woord het 'n goeie begryper nodig.

  • makesuthink - 2011-11-24 09:50

    See News 24 just employed Julius

      Grim - 2011-11-24 13:06

      ..classic

  • goyougoodthing - 2011-11-24 09:56

    Terrible grammar aside, the article would be more interesting if it spoke about the scientific possibilities of super chilled water. What does this mean in terms of making life better? Thermal dynamics, cooling computer chips, speeding up information transfers etc etc etc. Do some research first guys.

      Shistirrer - 2011-11-24 12:23

      One Jack and super chilled water, please. Hold the ice.

  • jpstrauss - 2011-11-24 10:06

    It was interesting, right up to the point where they started talking about global warming.

      vaaldonkie - 2011-11-24 14:27

      Yup.

  • ludlowdj - 2011-11-24 10:12

    anyone who has ever made ice cream already knows that water can be reduced to a temperature low enough to freeze milk without the water itself becoming iced

  • jeremy002 - 2011-11-24 10:18

    They needed to discuss the absolute feezing point of seawater in its varying levels of salinity in this little paper as well. How can they not mention seawater?

      robbie.crouch - 2011-11-24 11:04

      Computer models are still very flawed when it comes to weather due to the billions of variations each millisecond. It boils down to a very expensive thumb suck if you ask me!

  • zmasemola1 - 2011-11-24 10:27

    This was proven by a simulator programmed by professor x, y, z. What happened to "real world" experiments?

      TaniaSandraSteyn - 2011-11-24 16:27

      Very rude, Mrs-Pal.

  • i.R.womble - 2011-11-24 10:35

    They must be liking to be wearing jean pant.

  • MikeBrassellSA - 2011-11-24 11:01

    Oh wow. This has changed my life

      Robert Lance - 2011-11-24 11:04

      I agree, at least I can sleep tonight. Feel so much better

  • rory.short1 - 2011-11-24 11:14

    Science as I understand it is finding out about how things work and we need to know this if we are going to survive on this planet. There are now too many of to just do things withotu knowing what the consequences of our actions are going to be. Our forebears started using fossil fuels with gay abandon without any idea what the consequences would be. Now we know because it is impacting us, e.g. global warming and climate change, and yet there are still many who carry on promoting the use of fossil fuels. Are they just ignorant, mad or ecocidal?

  • Chrono - 2011-11-24 11:17

    The scientists among us can help, but I think I have read somewhere that super-compressed water also does not freeze, like water that is captured underneath a huge layer of ice. Apparently the pressure prevents freezing because in order to freeze the water needs to expand, but the weight upon it prevents the expansion.

  • Rob - 2011-11-24 12:48

    Why are the Science and technology articles soooo flippen outdated... Superfluids have been known about since the 50's... WE ALREADY KNEW THIS.

      vaaldonkie - 2011-11-24 14:28

      I think the point was to find out at exactly what temperature water is compelled to freeze.

      goyougoodthing - 2011-11-24 17:00

      Superfluids, such as metalli hydrogen, are made under pressure, this is a compound at normal air pressure as far as i can tell.

  • Zion - 2011-11-24 13:41

    Will this new theory hold water even if the water is under massive pressure and hence affecting the compressibility at an oceanic depth of say as deep as the Mariana trench 11miles I believe. I believe the tried and tested theory will still stand the test of time and still hold water.

      vaaldonkie - 2011-11-24 14:28

      meh.

  • pages:
  • 1