Physics and/or Chemistry Expertise Needed

General Questions
#1

I am fairly ignorant in hard science, but I think I’m correct on this one. Please back me up or explain why I am wrong.

I was discussing water with a friend today. In the course of the conversation, he said that H2O routinely breaks into H and O and reforms into H2O. In nature, with no prompting: electrical or otherwise. My understanding is that water is water and it is relatively stable, unlike hydrogen peroxide(H2O2) which does indeed lose its extra oxygen atom rather readily, becoming H2O. Am I right so far? He claimed that water molecules, at any given time, are constantly losing atoms and regaining them. No way!

There were some other things that didn’t make sense to me, but this one stood out.
My sense of the world is unstable enough without this (mis?)information. Help!

When you answer, please include your credentials. Hell, I can voice an opinion all day long, but it doesn’t mean anything!

#2

“Water is one of the most stable compounds in the world. It neither loses, nor gains atoms under normal circumstances. Of course, if you put some acid in it, you just might get a reaction…” - my chemistry teacher, today, ironically. (I am 16, in Chem II, Grade 11- enough credentials? I don’t know my Chem teachers’…)

#3

:ppppp I am 17 in OAC chem and I won the physics contest… but this really is a Chem question.

But he is right. Water doesn’t lose or gain atoms… it may lose or gain electrons having to do with whatever may be in solution with it, butnot whole atoms. It is in the lowest energy state while tetrahedrally bonded to two hydro’s and its two lone pairs of electrons. CAtoms and molecules like low energy, therefore it stays that way.

“C’mon, it’s not even tomorrow yet…” - Rupert

If you need a graphic solution, http:\ alk.to\Piglet

#4

yeah, what he said.
Credentials? I wouldn’t know what to do with one if I had it. I might play catch with it though, I think I missed a lot of that with the kids.

#5

In fact your friend is quite correct, but this behaviour is peculiar to liquid water and a very few other substances only. In the gas phase (steam) water is exceedingly stable, and does not come apart, as the previous folks noted.

But in the liquid phase water forms an extensive ice-like hydrogen-bonded structure. Essentially the oxygen atoms are in the middle of a vast network of bonds that connect them all to one another, with a hydrogen atom in the middle, joined to both oxygen atoms. (BTW any kibbitzers who want to assert hydrogen can’t do this don’t know enough physics to join this discussion.)

In ice this structure is stable, because so is the ice. But water flows, as I dare say you are aware, so the network is continually deforming, and individual links are breaking and reforming all the time. This means the hydrogen atom is continually losing one or the other of its oxygen partners. Sometimes it picks one, sometimes the other. In this way the hydrogens swap partners all the time.

This phenomenom of hydrogen exchange can be watched by NMR.

As a general rule, if a chemical reaction is possible in a liquid mixture of chemicals, then the molecules in question will be breaking up and reforming all the time. The chemical reaction that justifies your friend’s statement is the reaction of water with itself:

2 H[SUB]2[/SUB]O --> H[SUB]3[/SUB]O[SUP]+[/SUP] + OH[SUP]-[/SUP]

#6

What about heavy water?

YOu know what Id like? Some new water. Water that is made from fresh oxygen & fresh Hydrogen. Yummy.

#7

Forgot the credentials bit. I’m a professor of chemistry at the University of California.

#8

Water is normally at pH 7. pH means negative power of hydrogen. So ordinary water does in fact have a certain amount of free Hydrogen ions, and an equivalent amount of OH floating around. The exact amount is 10^-7 something, but I can’t remember the exact units.

#9

GC is correct with his assertion that at room temperature, the is a measurable concentration of H[sub]3[/sub]O[sup]+[/sup] is 1 n 10[sup]-7[/sup] molar. This is a dynamic equilibrium whereby exchange of H[sup]+[/sup] occurs rapidly between various H[sub]2[/sub]O molecules and OH[sup]-[/sup] ions. So, as such, it’s true to say that the bonds between H and O in water are constantly breaking and reforming, but of course this is the case for any molecule, although the energetics may be such that it’s difficult/impossible to detect the ions in all but the gas phase. Hope this code shit works.

#10

Well, some of that made sense. The essence of it is…I’m wrong again!

That’s okay; I’m used to it.

Could pure water be therefore considered a solution?

Please say no.

#11

NO
I have no basis to say that, but you wanted me to, so I did.

#12

Pure water itself would not be considered a solution because it did not involve dissolving one substance in another. Just because the substance happens to exist in several different forms (physically or chemically) does not mean that it is not “pure”.

TheDude

#13

And so we have another thread that lacks a solution. . . But that’s all water under the bridge.

Ray (and she’s all wet again)

#14

Elementary, my dear NanoByte. But water compounds the problem. With fluid reasoning, I thought my conclusion was solid. But I’m just blowing off steam now.

#15

handy: YOu know what Id like? Some new water. Water that is made from fresh oxygen & fresh Hydrogen. Yummy.

No, you wouldn’t. It’s the impurities in water (minerals, gasses, etc.) that give it some (if little) flavor at all. Otherwise, H[sub]2[/sub]O is bland as bland can be.

Ignore this: H[sub]2[sup]O[/sup]X[/sub]Z

#16

I suspect pure water really does have a taste but man evolved in such a way as to be unaware of it.

#17

AWB: I’m one of those odd ducks who actually likes the taste of distilled water. Bland, yes. But it has a purity to it that’s pleasant.