Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Formation of H2O?

  1. May 8, 2006 #1
    Has anyone ever formed water by manmade process? How is water formed and what conditions need to be met?
  2. jcsd
  3. May 8, 2006 #2
    Hydrogen & Oxygen and not much of an excuse to go Bang :P

    There are many condensation reactions that produce water, esterfication and so on.

    H3C-COO- Na+ + HO-CH2-CH3 + H+ → H3C-COO-CH2-CH3 + H2O
  4. May 8, 2006 #3


    User Avatar
    Science Advisor

    Manmade water is not very difficult to produce (I guess it would depend on your definition of manmade, it isnt really man making it, the chemicals arrange themselves into water).

    Burning Hydrogen gas with Oxygen gas will make pure water,
    2H2 (g) = O2 (g) --> 2H2O (g)
    This reaction is quite spontaneous (and explosive) one it has been ignited.
    This is the reverse process of splitting water apart [through elelctrolysis] into H2 and O2.

    Many other chemical reactions produce water as a product.
    Similar to burning Hydrogen gas, burning Hydrocarons (example, Methane or Octane) also produced water [amongst other things].

    Another exakmple would be a reaction between baking soda and vinegar. The reaction produces Carbonic acid (H2CO3) which quickly decomposes into Carbon Dioxide (bubbles) and water.

    Acid-Base neutralizations produce water too.
    The net ionic equation for the neutralization of a stron acid and a strong base is,
    H+ (aq) + OH- (aq) --> H2O (l)
  5. May 8, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    This can be the basis for a rather fun experiment. Take an ordinary party ballon and fill it two thirds full of hydrogen and and third full of oxygen. Then get a long stick with a lighted spill on the end and use it to pop the balloon, producing water.

    DISCLAIMER: I do not suggest that you actually carry out this experiement and I do not accept any responsibility for any damages / losses incurred as a result of carrying out this or any other experimentation. :tounge2: , just in case you blow yourself up. But seriously, don't try this at home.

  6. May 8, 2006 #5


    User Avatar
    Science Advisor

    You wouldnt need to put any Oxygen at all in the balloon (making the whole "experiment safer"), as when the hot flame melts the rubber balloon, the Hydrogen will immediately mix with Oxygen from the air and combust. Placing the Oxygen inside the ballon will only cause the reaction to proceed much more quickly and explosively. Instead, leaving the Oxygen source as the outside air (although still explosive) slows it down enough for you to actually see the fire ball.

    I have quite a few pictures and videos of myself doing this type of thing.
  7. May 8, 2006 #6
    mrjeffy321, thanks for the reply. When you say "burn," do you mean there must be an open flame, or an electric spark, or do you mean that water will be formed from hydrogen & oxygen gases if it hits the right temp, say in a chamber?

    I am looking for the most likely candidate for continued water formation on the earth. Really, in the earth.
  8. May 8, 2006 #7


    User Avatar
    Science Advisor

    In order for Hydrogen gas and Oxygen gas to react to form water, a certain amount of energy must be added to the system to start the reaction, this energy is called the "activation energy".

    Just mixing the two gasses is not enough to start the reaction, something needs to ignite it. An open flame would do it, a spark could do it, some type of heating element would also work.
    Once the reaction begins, the energy given off during the exothermic reaction is more than enough to keep it going.

    You usually dont find Hydrogen gas floating around free in the atmosphere or burried underneth the Earth, it is just such a light and reactive gas, this is not too likely.
  9. May 8, 2006 #8
    Is there and exhaustive list of reactions which you could recommend?

    They need to be earthly possibilities, not something theoretical. Repeatable science only.

    And do not try putting on your cosmological hard hats, or your geological sombreros. Although you look very cute in them.
  10. May 8, 2006 #9


    User Avatar
    Gold Member

    Who wants to see a fireball when you can feel a shockwave? :tongue2:
  11. May 8, 2006 #10


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What exactly are you looking for, again ?

    There's plenty of water on earth. Why do you want to make more ? Or do you think that would be easier than transporting it from one place to another ?

    In fact, even if and when hydrogen gets used as a fuel (sometime in the future), the combustion product is water, and that water is just going to be let out into the atmosphere. In other words, even when scientists/engineers build engines that make water as a by-product, they plan to essentially let the water go.
  12. May 9, 2006 #11


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hydrogen dissolved in the core plus oxides in the mantle yields water plus reduced iron, continuing the core differentiation from mantle rock; water moves up and iron "falls."
  13. May 9, 2006 #12

    Well, actually, if I really wanted to get a lot of fresh water somewhere, say to the Sahara, I would tow a nice big glacier from Antarctica.
    I am looking for help with how there came to be so much water in the earth. But I don't want to get kicked out of Chemistry over there to Cosmology, okay? Water is venting up from the mid-ocean ridges, and I believe personally that Antarctica's ice is flowing out from the center of the continent, and being replaced from some source. I am unsatisfied by the explanation that water came in on meteors. I want to know some likely candidates for water formation.
  14. May 9, 2006 #13
    mrjeffy, Suppose you did take H and O, and combine them in a chamber, with no air. Would the water produced be heavier than the weight of the two gases previous to the reaction? Can you get all the hydrogen to combine with all the oxygen? I can send you some more balloons. :)
  15. May 9, 2006 #14
    Wouldn't be heavier, but thanks to its propensity for forming hydrogen bonds, it would be denser.
    As to the "all the H with all the O" - depends on the proportions you have, obviously. And you would have to heat them somehow. I suggest irradiaiton.
    As the the "why is there so much water" query, let's look at it from an evolutionary perspective. The two compunds that make good solvents in which complex organic life could arise are water and ammonia, pretty much. We arose on a water planet, hence we are here to ask. On a planet covered in, say, liquid methane, we wouldn't be around to ask. That is why the planet we live on is not covered in liquid methane. It's not very satisfactory, I know, but it does make sense.
    (edited for spelling purposes)
    Last edited: May 10, 2006
  16. May 9, 2006 #15
    Is there a source you can let me look at for this model? Iron going down and water going up, that is good! Esp. with the earth spinning, you know how strong water pushes out when it is spun in a bowl, ahah. And then, you need the iron for the earth's dynamo, right? It fits pretty well, except, mrjeffy said you just don't find that much hydrogen going around looking for something to do.
  17. May 9, 2006 #16


    User Avatar
    Science Advisor

    In normal chemical reactions (as opposed to nulcear reactions), the law of conservation of mass applies....the mass of the products equals the mass of the reactants.

    If you take Hydrogen gas (H2) and react it with Oxygen gas (O2) to form water, then chemical reaction is as follows,
    2H2 (g) + O2 (g) --> 2H2O (g)
    If you calculate out the masses for the reactants and products for this reaction, they will be equal. 3 moles of gass (2 moles H2 + 1 mole O2) reacts to form 2 moles of gas (2 moles of H2O). The mass is the same on both sides, but the volume is decreased (especially after the water condenses into a liquid).
    In this reaction [just about] all the Hydrogen and Oxygen gas react very quickly and completely to form water vapor.
  18. May 9, 2006 #17


    User Avatar
    Science Advisor

    When very hot Iron (as one would find in the core) comes into contact with water...the extreme heat helps split the water up and releases Hydrogen gas and the Iron is oxidized.
    Why would Hydrogen "want" to be dissolved in hot, dense, Iron?
  19. May 9, 2006 #18
    "Wouldn't be heavier, but thanks to its propensity for forming hydrogen bonds, it would be denser."

    Thankyou, Tyris, I know it was a simple thing to say, and ask about. However, if all the water on earth were split apart, you are talking about an astronomical volume of gas, aren't you?
    Okay, so it would not be heavier, but it would behave a heck of a lot differently on a rotating planet.
  20. May 9, 2006 #19
    I had a feeling that was a silly question, but I needed to make sure as it has been more than 7 years since chem101 for me. I saw those (g)s in your first post equation, and was not totally sure it was grams. Sorry. It is just I could not imagine there ever having been that much O and H gas anywhere, to get all the oceans and aquifers. And the thing is, I was thinking about how that would affect the gravity force on earth. Now I am really going to get thrown out.
  21. May 9, 2006 #20


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Write the equilibrium expression for the iron-oxygen-hydrogen system. For extra credit, draw phase diagrams at several temperatures and pressures.

    Same thing that happens in any physical-chemical process, minimization of free energy.

    What you are examining is the "juvenile water" problem/question. As of 30 years ago, no analyses of volcanic gases had yielded conclusive data to confirm or refute release of hydrogen or hydrogen compounds derived from mantle or core material. Detection limits are high for isotope distributions, and the effect on isotope distribution is going to be small.

    Don't be running so far with the idea; density of water is what? Compared to density of iron? And, vapor pressure (activity, mobility) of water is what at mantle and core temperatures? Compared to same for iron?

    Do the math. What fraction of the earth's mass is the ocean? What fraction of the ocean's mass is hydrogen? What fraction of the earth's mass is the hydrogen in the ocean?

    You can also look at the solar wind; again, do the math.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook