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MIT Scientists Tackle Water Controversy

Discussion in 'Engineering & Technology News' started by Farjand, Aug 2, 2011.

  1. Farjand

    Farjand Rookie

    Engineering Discipline:
    Mechanical
    Water- the basic building block of life and many important processes has been a topic of wide debate and controversy. Controversy; in the sense that its properties although widely known,  still do not have a concrete explanation. Especially, the researchers have been trying hard to provide a satisfactory explanation to the anomalous behavior exhibited by water. Water is the only liquid rather a material which expands on cooling of course in the range between 0<sup>o</sup>C to 4<sup>o</sup>C. Human knowledge of this behavior of water molecules is still woefully incomplete.

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    Researchers Yang Zhang and Sow-Hsin Chen. Photo courtesy of the researchers

    A theory proposed 2 decades back suggests that a liquid-liquid transition similar to that exhibited by water can take place between two liquid states involving two different molecules of same liquid but with different densities. An MIT doctoral student Yang Zhang and Hsin Chen, professor in MIT's Department of Nuclear Science and Engineering and other researchers. Their research findings presented in the journal <em>Proceedings of the National Academy of Sciences</em><em> </em>supports the same controversial decades old theory.

    The study aimed to collect the data of water molecules when subjected to different pressures and temperature. The research although gives satisfactory conclusion supporting the theory, falls short of precise evidence. The main difficulty in obtaining the desired results is that, water cannot remain in a liquid state at temperatures below 0<sup>o</sup>C. The temperatures which Zhang has been experimenting with is around -60<sup>o</sup>C. The solution to this found in trapping water in tiny Silica tubes. The tight confinement keeps the water from crystallizing.

    Zhang did a thorough investigation of the properties of water molecules starting from a pressure of 1 bar to 3000 bar. He also varied temperature over a range of 170<sup>o</sup>C. Zhang then probed the density of water molecules through a neutron beam from a reactor at the National Institute of Standards and Technology. The conclusions he found out were very astonishing. He believes that "supercooled" water can be produced in any freezing instrument; even an ordinary refrigerator provided the water should be kept undisturbed. In a simple demonstration Yang Zhang kept a bottle filled with water overnight in freezer in a still condition, however although the temperature plunged below freezing point, the water didn't crystallize because there were no nucleation points like ripples or bubbles. Surprisingly as you create instability in the water, the water almost instantly freezes giving you with nothing but ice!

    Check out the video for above mentioned demonstration:

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    Pablo Debenedetti, a professor of engineering and applied science at Princeton University says,
    <blockquote>These are beautiful experiments that address one of the most interesting open questions on the liquid state of matter, and in particular on water: the possible existence of a phase transition between two distinct phases of liquid water.</blockquote>
    While there are also other results which can be derived out of the experiment. As we can produce supercooled water, we can also have "superheated" water in a microwave oven. But one thing is for sure, the research which gives sheds some light on anomalous behavior of water will have wide implications on things right from human health to construction business which involves using concrete containing tiny amount of water.  At a temperature of -45<sup>o</sup>C wide cracks may dangerously affect the structure of buildings in cold countries. Water which is a basic building block of life on earth, may sometimes affect us adversely. Perhaps a further research in avoiding this minimum temperature of water is necessary for technologies of the future.
     

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