The mystery of water ?

Discussion in 'Chemistry' started by thinking, May 3, 2010.

  1. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    To bend bounds form the natural 90 degrees require an energy source to do the work of bending. That is why I think the 105 degrees between the two protons is best thought of a due to the electrostatic repulsion between them - that can do the work of bending 90 to 105 degrees.

    Although one can define a radius for the proton, I have no idea what you mean by "bump up against each others van der Waals radius." How would that radius be defined? Do you think the 105 degrees is dynamic - increasing when they "bump"?
     
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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I explained why water expands below 4degrees C earlier* as follows:

    ‘… in my earlier post I suggested looking for the larger complexes, even possibly some rings, in 1degree C water as I agree the bonds between the units (++H2O--) of this complexes are weak and easily broken in hot water. But in 1 degree C water surely there are some complexes like:

    (++H2O--)(++H2O--)(++H2O--)(++H2O--)(++H2O--)
    and
    (++H2O--)(++H2O--)(++H2O--)(++H2O--) but not as straight as shown here. When these short strings of "H2O spaghetti" are randomly jumbled together in great numbers, there naturally occur voids to lower the density.”

    From: http://www.sciforums.com/showpost.php?p=2165729&postcount=86
    See also Trippy’s post 87, basically agreeing with my POV, but noting that room temperature water is mainly H2O with only a few of the dimmers
    (++H2O--)(++H2O--) which are individually short lived but there as new ones constantly form. This is true because the dimmer bond between these H2O units is weak.

    Point is cold water is very complex mix of “spaghetti like” units xH20 where average x increases as it cools below 4C as does the void fraction to make it expand.

    ---------------
    *I even suggested some experimental test / demonstration of these chain could be attempted in 1 degree water.
     
    Last edited by a moderator: May 4, 2010
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  5. Nasor Valued Senior Member

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    I was perhaps writing a little too informally. I agree that it is electrostatic repulsion between the protons (rather than between the bonding and lone pairs of electrons, as is commonly believed) that causes the protons to bend away from each other. Interestingly, in water the protons bend away from each other until they are about two van der Waals radii apart from each other, which seems to reinforce the notion that it is proton-proton repulsion that is causing the bending. The 105 degree bend certainly is dynamic and constantly changing, but I was referring to the ground state angle and distances. You can bend them closer together, but that will involve some sort of excited state.
     
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  7. Trippy ALEA IACTA EST Staff Member

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    No they don't.

    The VDW radius of a Hydrogen atom is 120pm (and it's covalent radius is 31pm).

    The O-H bond length has an equilibrium center to center radius of 95.87 pm.
    The H-O-H bond angle is 104.48°.
    Treating the water molecule in the plane defined by the H-O-H, it becomes an isoceles triangle, which can be treated as two back to back right angled triangles, each of which has angles of 52.24° at the vertex centered on the O atom, and the side opposite this being half the distance between the H Nucleii, and the length of the hypotenuse being the length of the O-H bond.

    The length of this second side can be calculated (remember SOHCAHTOA) as being 95.87Sin(52.24) which comes out at 75.79pm, which puts the distance between the Hydrogen nucleii at twice this, or 151.59pm which is a far cry from "twice the vanderwaals radius" (which would be 240 pm) and is nearly 5 times the covalent radius.

    In fact, by my reckoning, given that the maximum distance that could exist between the to hydrogen atoms (at equilibrium) would be 191.74pm, I reckon it's impossible to arrange them so that the two nucleii are 240pm apart.

    (incidentally, 95.87pm is remarkebly close to 31+66 (66pm being the covalent radius of Oxygen) especially when you consider there's an error of ±7pm in there).

    I have more to say on this. Much more, but for now, I'm out of time.
     
  8. Nasor Valued Senior Member

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    6,221
    It appears you are correct. My statement was a repeat of a claim made by professor Michael Laing in an old (1987) American Chemical Society paper discussing the bonding and structure of water. Upon closer inspection, it is clear that his claim was simply wrong. I'm surprised it was published like that.

    I will, however, stand by my original statement that the bending has to do with repulsion between the protons rather than between the lone pair electrons and bonding electrons.

    Thanks for bothering to check the math, Trippy.
     
  9. sifreak21 Valued Senior Member

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  10. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    What is there to capitalise on?
    It's crank "science".
    Apart from making money promoting it and then running away with the takings before the investors find out they've been duped.
     
  11. sifreak21 Valued Senior Member

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    1,671
    the fact that you can use tap water to power your car.. to cut steel tons of crap like that
     
  12. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    18,629
    Did you miss the words "crank science"?
    You can't (at least not without putting more energy in than you get out) power a car with water and how can you cut steel if the damn "flame" is cold to the touch?
    It's a fake.
    THAT'S why it hasn't been capitalised on.
     
  13. Nasor Valued Senior Member

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    6,221
    You can turn the water into hydrogen and oxygen gas, and then burn it as a fuel to power your car or cut steel. But it takes energy to turn water into hydrogen and oxygen, and you can't get back more energy from burning them than you spent making them. It's an okay way to store energy, but it's not a source of energy.
     
  14. Trippy ALEA IACTA EST Staff Member

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    I'm going to disagree with you here as well.
    I'm going to disagree with you on the grounds of sp³ hybridization, on the grounds that we should expect a lone pair to sit closer to the nucleus than a bonding pair, and on the grounds of how you can derive 109° in Methane from first principles assuming only that the molecule has, on average zero net dipole moment. I'm also going to go into more detail than that, when I find the time.

    NP.
     
  15. Nasor Valued Senior Member

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    6,221
    Water is not an sp3 hybrid. This is easy to prove with XPS spectroscopy. If water were sp3 hybridized, there should be two XPS peaks; one for the bonding electrons, and one for the lone pairs. This isn't what's observed. The fact that sp3 hybridization predicts approximately the correct geometry for water is merely a coincidence. The bonding in water is best described (without a proper molecular orbital diagram) as a sigma bond between the 1s orbitals on the hydrogen and two of the three 2p orbitals on the oxygen. This would give you a bond angle of 90 degrees, if it weren't for the proton-proton repulsion. Note that SH2 does indeed have to predicted 90 degree bond angle, because it's bigger, so the protons are still relatively far apart when at 90 degrees.
     
  16. sifreak21 Valued Senior Member

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    1,671
  17. Trippy ALEA IACTA EST Staff Member

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    I was going to address H[sub]2[/sub]S in my post as well

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    except I was going to make the point that H[sub]2[/sub]S → H[sub]2[/sub]Se → H[sub]2[/sub]Te is 92° → 91° → 90° for H-X-H bond angles, (I forget where I was going to take it from there).

    For now though, I'm simply going to point to the sign that says 'environmental chemist' rather than 'analyical chemist' 'spectroscopist' or 'quantum chemist', then make the point that my point was simply that all of these 'mysterious features' of water are trivially explainable when you consider the full picture.
     
  18. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Video claims passengers in life boat of sunken ship were able to drink the sea water until they could row to shore are not too far fetched as they were going from England to San Francisco and were probably off the coast of Brazil.

    Fresh water floats on salt water and when there is little wind you can be out of sight of land and drink the surface water the Amazon is pouring onto the ocean surface. No need for the link's nonsense about human emotions making the water fresh (or Christ turning water into wine) etc.

    What is fascinating is how quick people are to believe nonsense.
     
  19. sifreak21 Valued Senior Member

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    1,671
    i never stated or pointed tward me believeing it but some of the studies they do are interesting about growing plants ect and how animals will always choose natural water over tap its crazy i would like to see more studies on that.

    its not all nonsence water is very odd.. it is the only element when frozen it expands rather than contracts

    and the rice thing is very interesting too i might try that here soon
     
    Last edited: May 4, 2010
  20. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    23,198
    Being old is not much as so is beach sand molecules (Si2O3, I think, but Trippy knows), etc. certainly not protection against silly human beliefs about a substance.You may complain that these molecules are not as old as water, were part of rocks and even of chemical compounds, but so was water once.

    Interestingly if you drink a glass of water, there is a good chance that you are drinking a tiny bit of J. Caesar’s last piss.

    As far as water expanding when freezing, yes it does and I explained why most recently in this thread here:
    http://www.sciforums.com/showpost.php?p=2535274&postcount=42
    but years ago in other threads too.

    I am not completely sure but think that while expanding on freezing is very rare, water is not the only substance that does so.* Life would not exist if water contracted when it froze, so this property of water is very important.

    ------------------
    * As I understand why water does, I would expect many intrinsically polar molecules to do so.
     
    Last edited by a moderator: May 4, 2010
  21. Trippy ALEA IACTA EST Staff Member

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    Umm.

    No.

    As demonstrated here:

    2535084/34
     
  22. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    No mystery
    I would choose spring water over tap water every time.
    Water has a taste, and tap water tastes awful.

    To any animal with a good sense of smell it probably smells awful too.
     
  23. ArpusDogma Mere Sinndoor Registered Senior Member

    Messages:
    65
    water in a glass will not spin if you spin the glass with it
     

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