Why can we not say Water exist in 4 phases

Discussion in 'Chemistry' started by timojin, Dec 16, 2015.

  1. timojin Valued Senior Member

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    It was interesting discussion , I am familiar What rain is and how is formed , but I am not satisfied why the droplet organize themselves into a cloud . That does not obey the so called Grahams law if you remember
    from your early days of chemistry . repenner is forgiven he is not a chemist perhaps a physicist , they usually are hand wavers
     
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  3. rpenner Fully Wired Staff Member

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    You're the one advocating that clouds are somehow organized rather than being transient regions where more water is airborne than is allowed to exist at equilibrium as gas. It is the lack of any large-scale organization which results in them initially forming as myriads of unrelated tiny droplets. If there was organization all the water that was scheduled to be liquid would coalesce into a single large body of water which would plummet from the skies to devastating effect.
    Graham's law doesn't describe cloud behavior (including evolution) because droplets of water are not a gas. Graham's law (1848) applies to gases with the explanation coming in 1905 with the demonstration of the reality of the molecule from studies of Brownian motion and confirmed the theoretical basis for the kinetic theory of gases (1856—1871).

    The kinetic theory of gases is a more fundamental explanation than Graham's empirical law and as such it not only recovers the predictions of Graham's law in applicable cases, it gives us clear guidelines when Graham's law is inapplicable. That's the value of fundamental physics over empirical rules of thumb.
    An outrageous untruth expressed solely for some sense of unprincipled self-satisfaction.

    While trained primarily in physics, I have some experience with chemistry and the two once-unified fields are now approaching unification again via quantum chemistry molecular modeling.

    In one case, I saved a day of work by a professional chemist friend by the expedient of visualizing the organic synthesis he was attempting for the first time and saved him from throwing out the final desired product because it looked "gloppy." I did this over an Internet chat armed with my curiosity-driven independent research which led me to the same article he was reading. I pointed out that "gloppy" is the expected appearance of a waxy substance that melts near room temperature. Sure enough, it was the desired product.

    For the same reason that I could take technical details like the melting temperature, high molecular weight and waxy luster to synthesize in my head a visual model of what the product looked like, so my knowledge of fluid dynamics, geometric optics, the phase diagram for water, Coriolis effect and differential heating and lighting by the sun allows me to visualize how local phenomena like the equilibrium of phases of water at the boundary of a water droplet causes the large-scale phenomena of clouds.

    It takes work to synthesize emergent phenomena like the "puffiness" of clouds from a model of turbulent air flow and ephemeral droplets which can only stably exist when there is more water in the air than is needed to reach 100% vapor saturation. That's heavy lifting, not hand-waving. It's not the sort of thing than can be transmitted to someone balking at the prerequisites. But it's something that can be relied upon and is the same thing in principle which has allowed progress in weekly weather forecasts.
     
    Last edited: Dec 29, 2015
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  5. origin Trump is the best argument against a democracy. Valued Senior Member

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    Either you have not understood or your English is misleading.
    Droplets do not organize themselves at all. It all comes down to presure, humidity and temperature. If the local relative humidity is at 100% then any additional water vapor added will condense into dtoplets. If the relative humidity is at 100% and either the temperature decreases or the pressure decreases the water vapor will condense into droplets. That is how clouds form.
     
    Last edited: Dec 29, 2015
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  7. timojin Valued Senior Member

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    Thanks again.
    I know, droplets are not alive . Happen that molecules of gaseous water migrate into some environment , were condense into droplets or particles of water .
    Let me be nice to you . at 100% RH we have rain which is a product produced roughly 2000 mt above sea level.
    Perhaps an other correction "pressure decreases the water vapor will condense into droplets. " Why would that be ? I always thought as pressure decrease, the conversion of liquid to gas increase .

    Here are some nice pictures
    https://search.yahoo.com/yhs/search?p=rain clouds pictures&ei=UTF-8&hspart=mozilla&hsimp=yhs-003
    https://search.yahoo.com/yhs/search?p=cloud formation pictures&ei=UTF-8&hspart=mozilla&hsimp=yhs-003
     
  8. timojin Valued Senior Member

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    Rep. I know you are a brilliant guy and I am pleased you have participated on this post , It is better to disagree then agree . If agree the conversation stops there and there is not stimulation to learn better >
    So thanks
     
  9. timojin Valued Senior Member

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  10. exchemist Valued Senior Member

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    There is no such "compressive force". Where would it come from? Forces do not appear by magic from nothing.

    Water droplets coalesce by random collision with one another. The longer the cloud exists, and the higher the concentration of droplets (i.e. the "thicker" the cloud), the more coalescence will take place, because the time between collisions will be shorter. Eventually the droplets get big enough to have enough weight to overcome Brownian motion and the stirring effects of air currents, and they start to descend. And so we get rain.

    But if, on the other hand, the is cloud dissipating at the edges by re-evaporation, at a rate faster than that needed for this degree of coalescence, then we do not get rain, just clouds.

    That's it: no magic compressive mechanisms required.
     
  11. timojin Valued Senior Member

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    Read your second paragraph " thicker" the cloud), the more coalescence will take place" That means a lower mean free path , that means higher pressure in the middle of the cloud then on the edges of the cloud.
    Correct me. Brownian motion are related to fluid liquid , so the word Brownian motion would be in the water particle and nod in the partial pressure of particles and atmospheric gas.
     
  12. exchemist Valued Senior Member

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    OK, I will correct you.

    Lower mean free path between molecules of a gas would indeed indicate higher pressure. But smaller gaps between suspended liquid droplets means no such thing. All it means is more liquid droplets per unit volume, i.e. a greater mean density of the suspension.
     
  13. timojin Valued Senior Member

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    But that is ok
    All it means is more liquid droplets per unit volume, are you //That means a lower mean free path , that means higher pressure in the middle of the cloud then on the edges of the cloud.
    you want to apply density and density means you reduce the distance between particle, meaning Smaller distance to collide .
    A think from this discussion at 2000 meter the temp is low so the evaporation is low and the particle stay as particle and at the same time the atmospheric pressure is lower to keep the particle in air.
     
  14. paddoboy Valued Senior Member

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    Clouds are simply visible water condensate at different levels, their stability depended on pressures and temperatures.
    Warmer temperatures allow the atmosphere to hold more water than colder air, so that when a mass of air is cooled, simply put it rains...although again depended on pressures and temperatures, it could also hail or snow.
    So, yes, water exists as a solid, liquid or gas.
    That's science my friend...If you refuse to accept that, then you live in ignorance.
     
  15. exchemist Valued Senior Member

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    Do you really think the air pressure goes up when you enter a fog bank? Don't be silly.
     
  16. timojin Valued Senior Member

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    I am not sure if you can equate 2000 mt altitude were the temp. is about 3 C with the ground surface . Think as the crowd population gets larger the people in the middle in the crowd will have less space and pretty soon they will touch each other .
     
  17. exchemist Valued Senior Member

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    Cloud can form at any altitude at all from ground up to over 10,000m and the process is the same.

    Smaller distance between droplets does not increase the pressure, as water droplets are not rebounding elastically from one another, as molecules in thermal motion do.

    Just think a bit more carefully about kinetic theory. Increased pressure is a consequence of more momentum (mv) reversal as molecules hit the walls of a container. That requires either they move faster (higher temperature, greater v) or there are more rebound collisions per second (denser gas, greater m/sec). But the key feature is molecules in thermal motion, rebounding elastically.

    Water droplets are not molecules. They are passively suspended in air. They drift very slowly. So v ~ zero. When they encounter another droplet or the walls of a container, they do not rebound - on the contrary they stick and merge with the surface they encounter. Which is how they coalesce. So there is no pressure increase resulting from a denser fog or cloud (same thing).
     
    Last edited: Jan 14, 2016
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  18. timojin Valued Senior Member

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    Help yourself please examine a serie of diagrams and then if you like we will talk some more
    https://search.yahoo.com/yhs/search?p=cloud formation diagram&ei=UTF-8&hspart=mozilla&hsimp=yhs-003
     
  19. exchemist Valued Senior Member

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

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    Excellent post, hopefully timojin will read it with an open mind.
     
  21. paddoboy Valued Senior Member

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    I doubt it: This is just another effort to try and discredit science, as appears to be his mission.
     
  22. timojin Valued Senior Member

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    With do respect of your age , but you have a sick mind
     
  23. paddoboy Valued Senior Member

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    And you continue to be a fraud, as is shown by your refusal to accept scientific explanations, and making up total shit.
    Let me say again........................
    Clouds are simply visible water condensate at different levels, their stability depended on pressures and temperatures.
    Warmer temperatures allow the atmosphere to hold more water than colder air, so that when a mass of air is cooled, simply put it rains...although again depended on pressures and temperatures, it could also hail or snow.
    So, yes, water exists as a solid, liquid or gas.
    That's science my friend...If you refuse to accept that, then you live in ignorance. [as others have noted]
    Plus of course other even more detailed answers.
     

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