Interesting discussion, but I wanted to point out that the burning of fossil fuels (which Cecil says has created less than 1% of the water on Earth) isn’t the only way that water molecules are created & destroyed on the Earth. In fast, the natural carbon cycle is probably a much bigger factor. For example, plants use water and carbon dioxide to create glucose:
After this, further reactions will occur to make starches, cellulose, etc. When these plants die and decay/burn/are eaten, these reactions basically happen in reverse. In fact, the burning of fossil fuels is basically this process, just with a long delay between the creation of the carbohydrate and its destruction. And the water molecules that are consumed when the carbohydrate is created can’t really be said to be the same molecules that are released when the carbohydrate is destroyed.
These reactions have been happening for a very very long time — much longer than we’ve been burning fossil fuels — and it seems plausible to me that more than 1% of the world’s water molecules have been created/destroyed by this process. If so, then only some fraction of the water molecules in your glass of water are the same ones that were peed out by the dinosaurs. (Don’t worry, though: since there are a stupendous number of water molecules in your glass, you’re almost certain to have at least a few dinosaur-pee molecules in your class.)
Another factor to settle a squeamish mind is that the salt water and fresh water cycles are not separate. Fresh water rivers flow into the sea and salt water evaporates, forms clouds, and rains down on land. So you can console yourself with the thought that maybe, just maybe, all of the water in your glass is on its first trip around.
Reminds me of the example of the size of a molecule of water based on the idea that if you took a glass of water and threw it in the ocean, then waited enough time for it to distribute evenly throughout all the oceans, and then took a glass of water out of the ocean it would contain some water molecules from the glass of water you originally threw in. The point being that there are many more molecules of water in that glass than there are glasses of water in all the oceans. I’ve heard that disputed as in regard to the proportions though (and of course who knows how long or if all those molecules ever do get distributed like that).
During a lecture, our geology teacher at the community college once held up a piece of pyrite and ask us to figure it out in the form of ‘20 questions’. Took 19 for to be revealed as fossilized dinosaur dung. With some disbelief remaining a discussion arose as to how “the equivalent of soft tissue could have survived fossilization”.
With some brilliance, a student replied, “Tough shit. Deal with it.”
Cecil states that each hydrogen atom stays with an oxygen atom for a millisecond or so. Interesting and something I’d like to know more about! I’ve tried to search but it was impossible not to get a gazillion hits covering hydrogen bonds.
Where can i read more about it? Perhaps it’s common knowledge, but I never came across it during my 2yrs of chemistry studies!
The closest coprolite analogy I can come up with is an incestous realtionship between chemical resonance (or mesomerism) and van Der Waal forces. But that’s known scientifically as a “stupid guess.”
As my college chemistry knowledge has faded away and my Google-fu has not come up a harmonious answer to your question, I call upon the mighty and exalted Cecil to step down from His Throne of Wonderful Knowledge and explain where he heard about this exchange process…
slight hijack :you know its funny but this question reminds me of a joke that used to be said at a bar I used to go to
this guy who was about 80 and basically lived there would start this line about all these “mountain spring” beers saying ok coors was bear piss bush was rocky goat piss ect and hed go down the the list for about 20 minutes and everyone would roll off the stools …
And some newcomer would ask about light beer and hed go “you could make ya own light beer at home just get a horse and two buckets " fill one and put in front of the horse with <insert beer person was drinking> let the horse drink and run around 20 minutes or so lead horse over the empty bucket once he filled the second pour in bottle and chill”
Lets just say a time or two one of the beer guys caught his spiel and they were in no way impressed …all the old guy drank was wild turkey and maybe 7 up … oh and water 4 times a day hor the meds he took
The closest thing I can think about is the concentration of different ions at different pH, don’t remember what it’s called though (acid/base diagram perhaps) where most people (even chemistry students in lower grades, at least I did) think that there is only one ion present of for example carbon dioxide at a specific pH. The fact is that all ions (HCO3- and CO3(2-), H+, OH- and even H2CO3) are present at practically every pH, just at a different concentrations. The atoms keep jumping around forming different averages based on the current pH.
Some kids at the apartment complex where I live told me that they had just learned in school that we drink recycled toilet water. That was news to them, but it didn’t faze me because I already knew that, and I pointed at the nearby creek and told them that dinosaurs drank some of that water.
I can’t give any sort of meaningful calculation, but I’d guess that it’s at least somewhat right. When you get to dealing with stuff at the molecular level in liquid water, there’s going to be some self-ionization in the form of hydrogen ions (protons mainly) jumping ship from one oxygen atom to another when the molecule that they most recently were associated with bumped into another. The electrons in a water molecule are much more likely to be near the oxygen atom and the hydrogen ions are held rather loosely. Due to the absolutely constant collisions that occur in liquid phase, there’s always going to be some of the molecules that are out of perfect equilibrium, with the amount depending on the substance’s auto-ionization constant. For neutral water (pH 7), it’s approximately 1e-7; two of every 10 million molecules is ionized, one each way. For acidic or alkaline water, the negative exponent for the positive hydrogen ion changes according to the pH, so that’s why acids, which have high positive hydrogen ion concentrations, are lower in pH.
At equilibrium there are very few ionized, but the fact that there are any at all at such a state indicates that the equilibrium must be dynamic. There’s no way that any hydrogen ion is going to stay ionized when there are ten million other neutral atoms around it, plus one oppositely charged ion, which want that extra proton as much as it does. So it keeps getting passed around and around and around. The rate at which it meets its match is equal to the rate ions form through collision when the concentration of the hydrogen ion is equal to that auto-ionization level. There’s no way to say for sure that any particular molecule is exactly the same one as it was any length of time ago, but I’m sure if you find someone who knows stuff about statistical mechanics they might be able to give you an actual answer in terms of time frame of the ions jumping from one molecule to the next.
Note that often people talk of hydrogen ions as being protons (or deuterons if they have a neutron attached), but it’s probably more fair to say that the positive ions are in the form H[sub]3[/sub]O[sup]+[/sup]. It’s just easier as shorthand to write that as H[sup]+[/sup].
So you see that all 12 water molecules are broken down and six new ones are created. This has been noted several times using radioactively coded oxygen atoms.
Yes. I’m perplexed by the article’s separation of salt and fresh water. The oceans must be the largest source of water vapor (I think? Which has a larger surface area, the world’s oceans or the leaves of the world’s plants?).
Unfortunately, here in coastal California, the largest portion of our water supply is not recycled. From the mountains it’s used once, cleaned and then dumped into the ocean. Very little is reused.
Also, while two hydrogens are covalently bonded to an oxygen to form a molecule of water, in liquid water, there are numerous hydrogen bonds (between protons and neighboring molecules’ oxygens) forming and breaking as well. IIRC, there is no truly special status distinguishing the protons that are covalently bonded and those that are hydrogen bonded (this permits the ionization of water into OH- nad H3O+ described by glowacks); and the oxygen atoms can pretty much trade proton partners rather freely.
This is a dredged up memory, and I don’t have a cite; feel free to correct me if wrong.
I don’t recall where I saw it, but I did see something saying water that forms the comet tail does end up falling to earth or other bodies near it’s path. There was some figure of the amount of water that reaches earth from space, seemingly large, but small compared to the volume of water already here.
These are supposed to deliver about 1/2 inch - 1 inch of planetary water per 10K years.
This would also go nicely in that thread about “theories that go from woo to scientific acceptance”. Louis Frank proposed that house-sized chunks of ice were hitting the Earth’s upper atmosphere. Established astronomy said, “No.” His findings were explained away as artifact, until confirmed in 1997. I don’t know current status- maybe there has been a rebuttal.
