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Building upon the earlier critical point of water post…sort of February 8, 2010

Posted by Dr. O in Uncategorized.
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An interesting article regarding the phenomenon of ice nucleation recently published in Science.  Ice nucleation usually requires a “seed” of impurity around which to form, if there is no impurity, water can be supercooled and stay liquid far beyond normal freezing temperatures.  As most of us know, water molecules are polar, and thus, can be encouraged to “line up” according to charge and snap into rigid ice formation…and here’s where electric fields become important in influencing the behavior of water.

Excerpt: “A watched pot never boils, but an electrically charged pot sometimes freezes. A study in the Feb. 5 Science reports that water can freeze at different temperatures depending on whether the surface it rests on is positively or negatively charged. Under certain conditions, water can even freeze as it heats up.”

Definitely an article worth checking out!

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1. isotopeeffect - February 8, 2010

I would be interested to know a few things about this research – perhaps they are hidden away behind the Science magazine paywall.

I presume the workers used water of the highest purity available, to remove the presence of ions as a possible influence on the freezing behavior.

A look at the abstract of the Science article contains the additional intriguing tidbit that powder XRD studies show the freezing to begin at the water/air interface when the surface is negatively charged and at the water/surface interface when the surface is positively charged. I presume this means that the researchers also know whether or not the ice formed is ordinary hexagonal ice Ih.

In particular, I wonder if this new piece of research bears any relationship to this recent paper, which suggests that ice itself can be made to exhibit pyroelectricity in the presence of electric fields (induced in this case by the presence of ions).

Under normal circumstances, ice is considered to be an archetype of geometrical frustration, in that the water dipoles cannot all be aligned in the crystal lattice, leading to “configurational entropy” which was first calculated quantitatively by Pauling. Indeed, there has been a fair bit of research recently on systems called “spin ices”, in which it is magnetic dipoles that exhibit the “frustrated” behavior.

2. Dr. O - March 1, 2010

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