Has there been an improved understanding of water ?

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

  1. exchemist Valued Senior Member

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    6,477
    Well suit yourself. But it seems odd that if you think there is something of interest in this video you can't give us an inkling of what it is, so as to whet our appetites.

    My policy is to communicate in words on these forums, not just refer people to vidoes of unknown provenance without explanation. YouTube is full of shit, for example and this may be just more of it, for all I know.
     
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  3. river Valued Senior Member

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    Well go back to arauca's post , #120

    This video is not full of shit at all
     
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  5. wellwisher Banned Banned

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    An interesting use of water is to use water as a cutting tool for stone and metals. Water is pressurized and becomes dynamically harder than stone or steel. The speed of the water is so fast, upon impact with the solid object, the hydrogen bonds of water don't have time to adjust, so liquid water acts almost like a transient solid. While the very high heat capacity of water cools the cut, helping to prevent changes within the morphology due to heat. There is no waste and it is totally clean and recyclable.

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  7. Pantaz Registered Member

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    The vast majority of water-jet applications require the use of abrasives in the water stream.
     
  8. exchemist Valued Senior Member

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    6,477
    Yes and I very much doubt hydrogen bonds have anything to do with it either - I'm sure the apparent rigidity is just the effect of momentum - but Wellwisher seems to have a bee in his or her bonnet about H bonds, so we get this sort of time from time to time.
     
  9. wellwisher Banned Banned

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    If you ever played with silly putty, which is a silicone polymer, if you stretch it slowly it stretches like bubble gum. But if you stretch it faster with a jerk motion it will shear with a nice smooth cut. The polymer molecules need time slide past one another. If we use the quick jerk the molecules don't have time to move and get sheared at one plane.

    Silly putty will flatten with the slightest pressure and moldable like any putty. If you bounce it the ball will stay impact. It has to do with the rate of force and the time lag it takes for molecules to slide. Water does the same thing at high rates of motion. Silly putty is an easy way to prove it to yourself with direct evidence.
     
  10. exchemist Valued Senior Member

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    6,477
    Sounds highly implausible to me, I must say. And I can find no trace of any reference to this in articles about water jet cutting on the web. The Wiki one seems fairly detailed and mentions nothing of the kind: http://en.wikipedia.org/wiki/Water_jet_cutter

    Can you back up what you say with a source? If so I'll be interested to read it.
     
  11. origin Trump is the best argument against a democracy. Valued Senior Member

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    9,921
    As would I. All the water jets that I have been assocated with had an abbrasive material in the water, like SiC. If Wellwisher says that cutting with a waterjet has something to do with entropy I think I might scream.
     
  12. river Valued Senior Member

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  13. wellwisher Banned Banned

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    The hydrogen bonds don't have time to move like they would within a slow water stream, so the jet maintains low water entropy as it contacts the material, which gains the entropy.

    There are both ultra-high pressure (UHP) water jet and abrasive jet technologies. The UHP technologies begin at about 30,000 PSI. While current technology reaches over 60,000 psi and generates a stream of water at Mach 3.
     
  14. origin Trump is the best argument against a democracy. Valued Senior Member

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    9,921
    aaaaahhhhhhhhhhaaaaaaaaaaaaaaaaa!!
     
  15. exchemist Valued Senior Member

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    6,477
    bingo!!
     
  16. origin Trump is the best argument against a democracy. Valued Senior Member

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    9,921
    I have not seen the UHP water jets that do not use and abrasive before, thanks for the information.

    It is funny how your posts are typically a pile of bull shit but in the pile will be little scraps of accurate information.
     
  17. wellwisher Banned Banned

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    5,160
    Bias tends to make you blind. While lack of imagination prevents foresight.
     
  18. exchemist Valued Senior Member

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    6,477
    Returning to your hydrogen bond hypothesis for why high pressure water jets cut, if what you say were true, then a jet of high pressure water would be in effect a rigid rod. If that were so, once the jet had started to cut a groove in the work piece, it would resist being moved at right angle to the groove, in the same way that a circular saw blade cannot be moved sideways if it is in a cut it is making.

    But we do not observe this with a water jet. So your H-bond hypothesis is wrong. In fact, cutting with a blade is a way of concentrating enough localised force to push apart or dislodge particles from the work piece. Any blade does this and so does a water jet. There is no need at all for the jet to behave like something rigid: it just has to have enough momentum to create a strong local force, focused at the point where the cut is desired.
     
  19. origin Trump is the best argument against a democracy. Valued Senior Member

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    If this is direct towards me - I would have to say I my bias is to evidence and logic, that is why if you state something that is backed up by evidence and data I will accept it, but I will not accept stuff you make up. Imagination is important but imagination in science is not like the imagination used to write science fiction that is fantasy and quite a bit of your post are not science but fantasy.
     
  20. wellwisher Banned Banned

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    The problem is, some people require took much work to prove anything to. If my writing on the site turned into work, I would expect to get paid. If I am not getting paid, then I write for fun and to teach others. This hobby based approach keeps it enjoyable, and does not require I create a formal thesis for everything I say.

    When it comes to water I am well informed. I am often ahead of the curve extrapolating data you are not aware of.

    When it comes to water, one can infer most of its properties, if you understand hydrogen bonding. What makes hydrogen bonding unique is it exhibits both polar and covalent bonding character. The hydrogen bonding of water can actually switch between the two bonding states with only a small energy change, with the covalent slightly more stable.

    The polar aspects lowers potential by having the hydrogen bond get smaller so distances can decrease between charges. While the covalent aspects lowers potential by expanding the bond, so covalent bonding orbitals can overlap. Below is a schematic of the two states with a slight energy hill or energy barrier between. A is the polar configuration and b is the covalent configuration. The two states can switch back and forth due to closeness in energy, or remain stable in either state, due to the slight energy hill between.

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    Below is a picture of 280 molecule water clusters, common to water, where a wide range of hydrogen bonds switch between a and b, to form expanded and contracted conformations. Water has a binary switches within its hydrogen bonds. These binary switches also scale up such as in the binary cluster switches seen below.

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  21. wellwisher Banned Banned

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    If you ever heard the term surface tension, as applied to water, tension means stretching. That is implicit of the expanded covalent aspect of the hydrogen bonding. The logic is, since the covalent is more stable, it is needed to help compensate for surfaces where water is not able to lower its energy as well as it can, all by itself. By itself, water will use both A and B at the same time. But with organic surfaces, when tension is high, it goes heavy on the B.
     
  22. exchemist Valued Senior Member

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    6,477
    …………...And the relevance of all this to how water jets can cut is…………...what, exactly?
     
  23. exchemist Valued Senior Member

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    6,477
    As opposed to heavy on the BS, you mean?
     

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