Has there been an improved understanding of water ?

Discussion in 'Chemistry' started by river, Aug 16, 2013.

  1. Aqueous Id flat Earth skeptic Valued Senior Member

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    There are two kinds of bonds to consider. The one that joins 2H[sup]+[/sup] with O[sup]2-[/sup] is strong, and involves large amounts of energy. It's not in play here.

    The second kind is the Hydrogen bond which is due to a weak force (Van der Waals) between water molecules. When water freezes and thaws, it's this Hydrogen bond which will break and reform under cooling and heating.

    It's not H[sub]2[/sub] and O (?) changing phase, only H[sub]2[/sub]O. Note: H[sup]+[/sup], O[sup]2-[/sup], H[sub]2[/sub], O[sub]2[/sub] and H[sub]2[/sub]O are different chemicals, with entirely different properties. If you look at a table of melting points for various compounds and compare them to the bond energies involved in the formation of those compounds, you'll notice there is no correlation.
     
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  3. arauca Banned Banned

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    not D20
     
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  5. exchemist Valued Senior Member

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    River, I'm struggling to see what it is you do not understand here. Hydrogen burns to form water because the bond energies in water are stronger than in the hydrogen and oxygen molecules that are replaced: 2 H₂ + O₂ -> 2 H₂O. Water condenses at temperatures <100C (at normal pressure) because there are also these hydrogen bonds, which are stronger than the attraction between most light molecules.

    What is the problem, exactly?
     
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  7. arauca Banned Banned

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    If I would make comparison of water I would do it with H2S here the Mw twice of water jet is a gas at R.T. Formula: H2S
    Density: 1.36 kg/m³
    Molar mass: 34.0809 g/mol
    Boiling point: -76°F (-60°C)
    Melting point: -115.6°F (-82°C
    Electronegativity for S 2.59
    " for O 3.4

    What I would say the Hydrogen in water is held by more then one molecule of water and water should have a structure as a quasi crystalline
     
  8. KitemanSA Registered Senior Member

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    No, not heavy water, Polywater.
     
  9. wellwisher Banned Banned

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    At room temperature, the attraction between oxygen molecules O2 or hydrogen molecules H2 is weak, such that entropy, which among other things, is connected to disorder, is stronger causing these to be gases at room temperature. To make them liquify, we need to lower the temperature, to remove heat energy away from the entropy, so their weak attractive forces can begin to dominate to form a liquid.

    With water or H2O, the hydrogen bonding between oxygen and hydrogen is so strong that at the same ambient conditions, the entropy is not able to overcome to make water a gas, except as partial pressure vapor above the liquid, The result is water is a liquid.

    In terms of an equation we have G = H -TS where G is the free energy, H is the enthalpy, T is the temperature, and S is entropy. With O2 and H2, the TS term is dominate because the weak attractive forces or H between O2 or H2, is tiny. With water H is huge and TS is small by proportion.

    This huge H contribution in liquid water is important to life since it helps push the organics of life into order by making their TS smaller by comparison. We shake water and oil and add energy the entropy will increase to form an emulsion. But shortly the H will take over and lower the entropy/disorder until only two layers remain.
     
  10. river

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    Are you saying that entropy is a force ?
     
  11. Russ_Watters Not a Trump supporter... Valued Senior Member

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    I don't think you are understanding what a molecule is. A molecule is the smallest unit of a substance that retains/determine its chemical properties: the macroscopic properties we observe such as color and boiling temperature. So water and molecular oxygen are completely different molecules, which means their boiling points should not be expected to be related in any way at all.

    http://en.wikipedia.org/wiki/Molecule
     
  12. river

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    I don't get what saying here

    Water is H2 - O

    There is no molecule of O2
     
  13. origin Trump is the best argument against a democracy. Valued Senior Member

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    Yes there is - that is the stuff in the atmosphere that is keeping you alive. A molecule of \(O_2\) is made up of 2 oxygen atoms.
     
  14. river

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    We are discussing water here though , not the atmosphere
     
  15. origin Trump is the best argument against a democracy. Valued Senior Member

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    Geeze, this is your thread. You started the thread talking about H2, O2 and H2O not just water. So, do you get why there is the difference in the boiling points?
     
  16. river

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    Sure because of atmospheric pressure

    So we still don't know whether H and O , so a single atom of each has the ability to form a liquid on there own ?

    Interesting
     
  17. origin Trump is the best argument against a democracy. Valued Senior Member

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    Ha ha, no need to be sarcastic.
     
  18. river

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    Sarcastic ?
     
  19. Russ_Watters Not a Trump supporter... Valued Senior Member

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    H and O are diatomic molecules. They do not exist as single molecules in either their normal liquid or gas forms.
     
  20. river

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    Yes but it would be interesting to find out whether both H or O could on their own , single atoms , produce a liquid state
     
  21. arauca Banned Banned

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    if you mean a free radical O and a free radical H, I would think the half life of such radical would be very short and they will become ionized into O- and H+
     
  22. river

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    Yes I suggest free radical

    So your saying that a lone H atom or O atom cannot survive alone , but we don't know this , its a thought rather than knowing
     
  23. arauca Banned Banned

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    I think because the nature of electronegativity of oxygen it will get the electron from some of its surrounding or it will interact with an other oxygen to share its unfilled orbital .
     

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