Comments on: How Water Freezes Lower on a Negatively Charged Surface http://www.chemistry-blog.com/2010/02/10/how-water-freezes-lower-on-a-negatively-charged-surface/ We have technical difficulties, it will take a day or two to get back to normal. Sun, 05 Sep 2010 15:07:35 -0700 hourly 1 http://wordpress.org/?v=3.0.1 By: orgopete http://www.chemistry-blog.com/2010/02/10/how-water-freezes-lower-on-a-negatively-charged-surface/comment-page-1/#comment-10068 orgopete Thu, 11 Feb 2010 13:34:27 +0000 http://www.chemistry-blog.com/?p=3636#comment-10068 Re: one or two protons attracted? My thinking was the differences in freezing points must be essentially an entropic effect. After all, both do freeze. I could not think of why water should back in more slowly to a fixed matrix than forward. It seemed to me, the effect is more a question of which atoms are moving on a micro scale. In terms of movement, it shouldn't matter if a proton from an attacking water moves more than an electron pair. Therefore, if both protons were attached, there shouldn't be a difference in the freezing points. I agree with the stacking argument. I thought it must be something else. I agree with your electron density map making it appear little difference is present in the molecule and that a general dipole exists as drawn from the oxygen toward both hydrogens. However, I believe the strongest hydrogen bonding occurs along the H-O axis. (The best example of a variance I can find is the enol form of a diketone, such as acetylacetone.) Accordingly, I thought water would most likely bond similarly to an electron pair on the surface. If that were so, I thought the free rotation of the other hydrogen could inhibit productive collisions for freezing. Re: practical? Well, that is putting the screws to this. I have taken some time to think about it. Could this be related to rain making? If you wanted to make it rain, you would seed clouds with silver ions. We know that silver nitrate impregnated TLC plates can coordinate with alkenes to alter their elution. Therefore, silver crystals may present a surface to coordinate with the non-bonded electrons of water and enable condensation. If that were true, then we could consider searching for a similar molecular property. (I am only guessing that seeding clouds was done by trial and error and may not have undergone a more modern re-examination. If someone knows better, they may correct me. I have not researched this.) Re: one or two protons attracted? My thinking was the differences in freezing points must be essentially an entropic effect. After all, both do freeze. I could not think of why water should back in more slowly to a fixed matrix than forward. It seemed to me, the effect is more a question of which atoms are moving on a micro scale. In terms of movement, it shouldn’t matter if a proton from an attacking water moves more than an electron pair. Therefore, if both protons were attached, there shouldn’t be a difference in the freezing points. I agree with the stacking argument. I thought it must be something else.

I agree with your electron density map making it appear little difference is present in the molecule and that a general dipole exists as drawn from the oxygen toward both hydrogens. However, I believe the strongest hydrogen bonding occurs along the H-O axis. (The best example of a variance I can find is the enol form of a diketone, such as acetylacetone.) Accordingly, I thought water would most likely bond similarly to an electron pair on the surface. If that were so, I thought the free rotation of the other hydrogen could inhibit productive collisions for freezing.

Re: practical?
Well, that is putting the screws to this. I have taken some time to think about it. Could this be related to rain making? If you wanted to make it rain, you would seed clouds with silver ions. We know that silver nitrate impregnated TLC plates can coordinate with alkenes to alter their elution. Therefore, silver crystals may present a surface to coordinate with the non-bonded electrons of water and enable condensation. If that were true, then we could consider searching for a similar molecular property. (I am only guessing that seeding clouds was done by trial and error and may not have undergone a more modern re-examination. If someone knows better, they may correct me. I have not researched this.)

]]> By: claud http://www.chemistry-blog.com/2010/02/10/how-water-freezes-lower-on-a-negatively-charged-surface/comment-page-1/#comment-10060 claud Thu, 11 Feb 2010 02:12:36 +0000 http://www.chemistry-blog.com/?p=3636#comment-10060 Nice write up. You certainly put a lot of effort into it (more than I ever do...). Now, is there a practical use for this nifty result? Nice write up. You certainly put a lot of effort into it (more than I ever do…). Now, is there a practical use for this nifty result?

]]> By: mitch http://www.chemistry-blog.com/2010/02/10/how-water-freezes-lower-on-a-negatively-charged-surface/comment-page-1/#comment-10057 mitch Wed, 10 Feb 2010 23:14:04 +0000 http://www.chemistry-blog.com/?p=3636#comment-10057 Although the flagpole looks appealing, I don't see why both protons couldn't be on the surface as these are just coulomb interactions (charge with partial charge) not proton dissociations. More opposite charge touching the stronger the interaction. If I were to look at the electron density map of water: <img src="http://xnet.rrc.mb.ca/rcharney/The%20water%20molecule_files/molecul2.jpg" alt="" /> It would seem easier to stack water molecules with two protons on the charge surface, than stacking water molecules on the rounded edge of the lone-pair electrons. Molecules that stack well have lower freezing points than molecules that don't stack well. Although the flagpole looks appealing, I don’t see why both protons couldn’t be on the surface as these are just coulomb interactions (charge with partial charge) not proton dissociations. More opposite charge touching the stronger the interaction.

If I were to look at the electron density map of water:

It would seem easier to stack water molecules with two protons on the charge surface, than stacking water molecules on the rounded edge of the lone-pair electrons. Molecules that stack well have lower freezing points than molecules that don’t stack well.

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