Can water be broken down into it's core elements?

Factual Questions
1

Please help settle an argument:

Stoid says:

Over the last billion years, the total amount of water above, on and in the earth has been the same. There is no new water, and there hasn’t been any loss of water. Sometimes it changes form (vapor, ice, liquid), but it’s always the same water.

I say:

Water can and regularly does get broken down into it’s core elements which can be used to form other compounds. This is accomplished by photosynthesis, electrolysis, combustion and any number of things.

So who is (more) correct?

2

Water is constantly being broken down and reused in other compounds.
[ul]
[li]The source of most life energy on Earth, photosynthesis, takes carbon dioxide and water and makes a simple sugar (glucose?) and molecular oxygen, O[sub]2[/sub].[/li]
[li]Water is a constituent of many minerals, but they aren’t “wet”. The water molecule is still together, but it’s an intregal part of the mineral’s structure.[/li]
[li]In the upper atmosphere, water is hit hard enough by incoming radiation to knock it to pieces. It reforms into various molecules. If any H[sub]2[/sub] is the result, it probably leaches off into space before it has a chance to react with anything else. So we’re probably losing hydrogen all the time.[/li]
But not to worry. Nuclear decay often emits lone protons, which eventually attract the stray electron, and viola, a new hydrogen atom is born.

[li]Electrolysis by humans, relatively small potatoes compared to photosynthesis, rips water into H[sub]2[/sub] and O[sub]2[/sub]. Nuclear subs do this to get their breathing oxygen, so they can stay underwater indefinately.[/li][/ul]

3

Oh, and cosmic debris (mainly comet leavings) falls to Earth all the time, containing ices, usually methane and water. So we’re getting water input to our ecosystem all the time.

4

I dont know for sure, but in chem. class (a long time ago) we added electric to a vile of water. when finished we had O2 on one side of the gizmo, and Hy on the other, thought not an efficiant form of energy, i dont think it ever turned back into water. sorry could not help much

5

Not only that, but the combustion of any hydrocarbon produces carbon dioxide, and…water!

You may have seen water dripping from cars’ tailpipes. There’s a reason there was water up there. It’s been condensing on the inner walls of the tailpipe, even as hot as it is.

6

whom I love and respect above all other persons, and who is, in my opinion, the smartest person I personally know… he has sorta blown it on this one.

First of all, the very title of the thread, “Can water be broken down into it’s core elements?” is a question he asked while he was composing this thread, and I answered: “YES, I concede that it is possible” because PAG proved that to me just a few weeks ago. So that is not really the source of argument.

What appears (since I’m not entirely sure still what exactly it is he’s arguing with me about) to be the argument is this:

As stated in the OP, I maintain (not because I am any kind of science weenie, but merely because it is what I learned 35 years ago, and what I have had repeatedly confirmed in the intervening years) that the amount of water on earth is relatively constant, AND it is pretty much exactly the SAME water that it has always been. It is not “new” water. Nor has there been any significant loss of the water we have. While it may be possible to destroy water and make new water, it is not something that happens with any regularity on Earth, nor does it in any way affect the water supply we have now and have always had and will almost certainly always have.

My cites for this are as follows:
http://observe.ivv.nasa.gov/nasa/earth/hydrocycle/hydro1.html

It’s true, the water we use today has been around for hundreds of millions of years, and the amount available probably hasn’t changed very much. Water moves around the world, changes forms, is taken in by plants and animals, but never really disappears.
http://www.nps.gov/bela/html/history.htm

Because the amount of water in Earth’s hydrospere is constant, the great ice sheets’ hoarding of global waters caused sea levels to fall significantly. As a result, land masses grew dramatically where continental shelves slope gradually, as they do in the Bering Strait.
http://www.lbl.gov/Education/ELSI/Frames/sustain-water-f.html

The amount of water in the world stays the same and is constantly circulating between the oceans, the atmosphere and land.

http://www.schoolzone.co.uk/resources/geog.htm

There is about the same amount of water on earth now that there was when the dinosaurs roamed our planet.
http://www.kidzone.ws/water/

The earth has a limited amount of water. The water in your glass may have fallen from the sky as rain just last week, but the water itself has been around pretty much as long as the earth has!
According to the Acadamy of Natural Sciences…

http://www.acnatsci.org/education/skytosea/bigdeal.html

The amount of water on the Earth today is the same as it was billions of years ago. There is no more and no less. Water is continually recycled through what is called the water cycle or the “hydrologic cycle”. Water changes its form throughout this cycle. It can exist as a solid, liquid, or gas. It also changes its location. Water moves over the Earth’s surface, underground, or through the atmosphere.
http://www.ec.gc.ca/water/en/info/pubs/FS/e_FSA2.htm

“the total quantity of water on the earth’s surface remains essentially constant”.

http://www.lsu.edu/university_relations/oceancommotion/fastfacts.htm

Today, the earth has approximately the same amount of water as when it was formed; the earth will not receive additional water.

  • The water consumed today may have been a drink for a dinosaur.

http://octopus.gma.org/katahdin/water.html
The Water Cycle can change the form of water from liquid to water vapor to ice, and even clean it along the way, but it can’t make more water.

http://csd.unl.edu/esic/pamphlets/hydro-cycle/hydro-cycle.html

The waters of long geologic history are the waters of the 20th century; little has been added or lost through the ages since the first clouds formed and the first rains fell. The same water has been transferred time and time again from the oceans into the atmosphere, dropped upon the land, and transferred back to the sea.

http://www.prb.org/child_six_billion/water.htm

“But the amount of freshwater on the planet is finite,”

And there you have it.

7

I suppose it’s true that most of the water that was here after the earth’s formation is still here as water. However, a significant amount has gone away. The proof of this is our atmosphere, which contains about 21% oxygen (working from memory, may not have the exact number there). That oxygen did not originally exist here, and was created mostly by the action of plant life. The oxygen was created by breaking down water and carbon dioxide.

I’m not sure how much O[sub]2[/sub] comes from CO[sub]2[/sub] and how much came from H[sub]2[/sub]O, but at least some came from water, right? And there’s a lot of O[sub]2[/sub] around. Can someone more knowledgeable about plant metabolism tell us more?

This O[sub]2[/sub] is constantly recombining into compounds, with H[sub]2[/sub]O being a common product. Then, the plants make more. So water is constantly forming and disappearing, though I’m not sure exactly how much of all the water is involved in the process.

8

The statement “Over the last billion years, the total amount of water above, on and in the earth has been the same” is a good approximation. Amending it to “Over the last billion years, the total amount of hydrogen and oxygen above, on and in the earth has been the same” makes it an even better one.

A billion (10[sup]9[/sup]) years ago, photosynthetic life was well established. The free oxygen content of the atmosphere was much lower, but that was because early releases of free oxygen didn’t accumulate as gas, but went into oxiding low-valence metal compounds into higher-valence ones (most notably ferrous to ferric). Since low-valence ions are usually fairly soluble, and high-valence ones are not, the loss of dissolved nutrients may have caused an even greater ecological devastation than the mere toxicity of free oxygen did. The total amount of biomass hasn’t increased by much since then, however.

(Note to Saltire: the oxygen released by photosynthesis always comes from water, as is shown by experiments using water and carbon dioxide tagged with [sup]18[/sup]O. This is because chlorophyll doesn’t use water per se, it uses hydrogen.)

As AWB points out, the Earth loses water by photolysis (the dissolution of water into hydrogen and oxygen by UV photons) and gains it from space debris. This likely more or less nets out, though, and isn’t significant in either case.

9

Chlorophyll uses water as a source of electrons, oxidizing it to make molecular oxygen and protons. The oxidation state of the hydrogens does not change, it stays are +1. It is the oxygen that loses electrons to change from the -2 oxidation to the 0 oxidation state. I’m not sure what you mean by “chlorophyll uses hydrogen.”

Here is a diagram of the flow of electons in the light reaction phases of photosynthesis

10

You’re actually making two assertions here. One is that the amount of water on Earth is always constant, and the other is that there is no “new” water. In other words, the water in my glass has been water for the last billion years.

I think we all agree that water can be broken down into hydrogen and oxygen. Since this is possible, wouldn’t every single water molecule have to be recombined in the exact order it was broken down to be the “same” molecule of water?

Here is a hypothetical example. Pretend there are several billion cubes. Each is composed of two lego blocks. Now, break apart several million cubes on a daily basis and scatter the pieces around. Combine them back into cubes, and you now have as many cubes as you began with. Of course they all look identical to the original cubes, but they are not the same cubes.

It doesn’t happen with any regularity on earth? What about PHOTOSYNTHESIS?

Going back to the lego example, let’s say some of the blocks were not combined back into cubes. Rather, some were used to form larger structures, and some were not recombined at all. You still have all the pieces you originally started with, but you now have fewer cubes.

Here are some quick questions for you. If you have six molecules of water and six molecules of carbon dioxide, how much water is there? If those are combined to form one molecule of sugar and six molecules of oxygen, how much water is there?

Most of the cites you list are in relation to the natural water cycle. It’s true that this can’t produce any more water, but that doesn’t mean that water can not be lost by other means.

11

Mix the two and apply a match. They turn back into water in a fairly interesting way. AMHIK :wink:

(it involves a large party ballon, two parts pure H[sub]2[/sub] and one part welding-grade O[sub]2[/sub]) :smiley:

12

I hate to keep ganging up on you, Stoid, but one of the problems with science is that if you don’t define your terms unambiguously, someone’s going to come along and look at them in a different way.

There is a process that ‘destroys water’ almost constantly, and is occurring in every little bit of liquid water everywhere in the universe. Within every mole of liquid water, there is 10^-7 mole of H+ ions and 10^-7 mole of OH - ions. How did they get there? Well, about every ten millionth water molecule has dissociated into its components. This happens spontaneously, and molecules dissociate and recombine at the same rate, and although I have no idea what that rate might be, I feel quite safe in saying that pretty much every water molecule that existed a billion years ago on Earth has since dissociated, and the molecules that exist now have all been formed from the component ions of different molecules in the meantime. So the components are the same, and in that sense I’ll grant you that we likely have much the same water (remember, folks, organic processes don’t use up a very large proportion of the water out there!) that we did a billion years ago.

Not that it much matters. Up to differences in isotopes, any two given water molecules are as good as chemically identical, whether they formed a microsecond or a gigayear ago.

[hijack]
Speaking of differences in isotopes, I’ve always wondered: Is ‘heavy water’ really D2O, like all the books claim, or is it really HDO? My statistical gut says that there is way more of the latter than the former.
[/hijack]

13

Just to help out the non-chemmy types, that’s supposed to look more like 10^ -7 moles of both H+ and OH- ions.

In other words, pretty darn small amounts.

Mr. D, I think, considering the small amounts of deuterium, heavy water would almost have to be HDO, wouldn’t it? Unless you somehow made water in a lab with larg bottles of deut. obtained from what, a mass spectrometer or something?

14

Of course if you ever had a bottle of DHO it wouldn’t stay that way for long because of the rapid disassociation of water molecules you would quickly get a lot of D[sub]2[/sub]O and H[sub]2[/sub]O mixed in. I’m not sure how heavy water is isolated, but I’d guess if you purify it enough times you could get pure D[sub]2[/sub]O. Persumably, for most purposes getting the highest level of deuterium possible would be the goal, but I have no idea the actual content of heavy water.

15

[QUOTE]
*Originally posted by Dave Swaney *
**

Pure D[sub]2[/sub]O is readily available. Go to http://www.sigma-aldrich.com and search for deuterium oxide. They sell products containing varying percentages of it, of course.

16

Yes, you are correct that chlorophyll uses the excess electrons on hydrogen ions, which I attempted to simplify as “chlorophyll uses hydrogen” (once again, I underestimated the sophistication of the Teeming Thousands). I also thought it important to note, however, that chlorophyll wants the electrons attached to the hydrogen ions, and is essentially unconcerned with what that hydrogen started out combined with. Green sulfur bacteria use a chlorophyll to split hydrogen sulfide.

17

Ahhhhhh…of course! That makes sense now; so you isolate
HDO from regular water, wait X amount of time, and isolate the resulting D[sub]2[/sub]O! Neat!

18

Looks reasonable. I almost burst a gut when I looked it up and saw under the entry:

I mean, heck, it makes sense that water would be hygroscopic, but it’s one of those things you don’t think about beforehand :slight_smile:

19

Wait, why would the Ds attract each other? Why would we end up with DDO instead of HDO? And about isolating it, all I can think of is mass spectroscopy and distilling. Wouldn’t these be pretty impractical?

20

If you drank a bunch of heavy water, would your body be able to use it normally? And what do you call water that has tritium in it (besides radioactive, that is)?