splitting a froghair three ways-or, who is right?
January 5, 2011 3:53 PM   Subscribe

Does compressed oxygen burn? Or do only objects IN compressed oxygen burn? Please settle this dinnertime discussion...The hubs and the daughter's boyfriend need to be told which one of them is right. Thanks!
posted by St. Alia of the Bunnies to Science & Nature (19 answers total)
 
Oxygen does not burn. Oxygen reacts with other materials help them burn. So something that is flammable will burn faster, and more completely, in compressed oxygen, since compressed oxygen means a higher amount of oxygen molecules are available.
posted by EndsOfInvention at 3:55 PM on January 5, 2011 [1 favorite]


Well, unless someone else chimes in here, sounds like husband won....
posted by St. Alia of the Bunnies at 4:02 PM on January 5, 2011


The interesting thing is that a jet of oxygen in a methane environment, ignited, will create something that looks just like a flame.

Nonetheless, the above poster is correct: other things burn in oxygen. (And flourine, which does it even better.)
posted by Chocolate Pickle at 4:02 PM on January 5, 2011


The question is one of definition. For combustion or burning to occur you need two things -- a fuel and an oxidizing agent. By definition, the fuel burns in the oxidizing agent. Both fuel and oxidizing agent are chemically changed but (by definition) only the fuel "burns". For example carbon (in the form of charcoal) is a fuel and will react with oxygen (oxidizing agent) to form a new compound, carbon dioxide.

Oxygen is the most common oxidizing agent (there is a reason for the similarity in the words oxygen and oxidizing...) and it is also one of the strongest. Because oxygen is such a strong oxidizing agent there is nothing that will oxidize oxygen, hence oxygen does not "burn". However, oxygen is (almost) always a required component of a flame. (cite)
posted by misterbrandt at 4:03 PM on January 5, 2011


Compressed oxygen is still dangerous, of course. It's marked with an oxidizer safety sign because it can make things burn readily (this is differentiated from the flammable safety sign).
posted by zsazsa at 4:05 PM on January 5, 2011


To confirm and expand upon St. Alia's answer, oxygen is necessary for combustion, but is not a fuel.
Technically, oxygen does not "help" things burn; it is a necessary part of the combustion process in that the oxygen bonds with molecules of the fuel to form an oxide. The process we are most familiar with is oxygen bonding with carbon atoms to form carbon dioxide, CO2. In the absence of fuel, you can hold an open flame in a stream of pure oxygen, and nothing will happen. This is, of course, why the atmosphere (which is 21 percent oxygen) doesn't explode when you light a match.
posted by dinger at 4:11 PM on January 5, 2011


Oxygen will burn, be oxidized, in the presence of fluorine. Compressed oxygen can burn many other things (but not everything), but it is possible to burn O2.
posted by bonehead at 4:11 PM on January 5, 2011 [1 favorite]


Yeah, as others have pointed out, you need a fuel to burn.
posted by orthogonality at 4:26 PM on January 5, 2011


If I may slightly re-state what others have said slightly differently:

Take a wooden stick. Light it on fire. So it's burning, aka oxidizing. It's doing this using the available oxygen in our regular air down here where the humans live.
If you blow on it, it burns faster - because you are exposing the fuel (the wood) to more oxygen. That's why you often blow on the kindling when trying to start a campfire.

If you were to put that little wooden stick into a little jar of pure oxygen, not compressed, it would just about explode - it would oxidize extremely quickly in a bright flash. (no smoking in the oxygen tent at the hospital - the cigarette will explode - probably taking the lighter with it as a byproduct)

For compression: This is how a turbocharger/supercharger work in vehiclese... they force more air into the cylinder so that more fuel can be burnt on each stroke, releasing more energy.

dinger: You're technically right - but that could be misinterpreted badly - if you have a flame that means you have a fuel. If you light a match and then spray pure oxygen from a tank onto it, it's going to pretty much burn in a flash like magnesium, probably causing 3rd degree burns on your hand along with it.
posted by TravellingDen at 5:05 PM on January 5, 2011


So here's a bit more info.

Oxygen was first reported "burned" in fluorine by Otto Ruff and Walter Menzel in 1933, forming the dioxygen difluoride with the exceedingly appropriate molecular formula FOOF. In this molecule, by classic electron pair theory, the fluorine is in it standard form of -1, implying that the oxygen is in an astounding +1 oxidation state: oxygen, oxidized!1

FOOF is very apt. That's exactly what it does if allowed to touch, well, anything. Oxygen hates being electron-poor, and doubly electron poor at that. There are many good reasons not to want to monkey with the stuff. Sensible chemists don't want oxygen fluorides anywhere near their lab.

1 FOOF wasn't the first discover oxygen fluoride, that would be oxygen difluoride in 1929, but it was the first reported prepared by direct reaction, burning in other words. A fine distinction, but, I think, an important one.
posted by bonehead at 5:15 PM on January 5, 2011 [2 favorites]


I'm interested in this flourine diversion. So I understood that "burning" *mean* "combining with oxygen". One poster stated that oxygen will burn in the presence of flourine. Wouldn't it be the flourine that's burning?
posted by smcameron at 6:26 PM on January 5, 2011


Also, if you had a bunch of free floating individual oxygen atoms, wouldn't they "burn" (combine with each other) to form O2? (And now this makes me wonder if the presence of flourine makes Oxygen "burn" as in: 3O2 --> 2O3 (makes ozone) somehow.)
posted by smcameron at 6:28 PM on January 5, 2011


Ugh, somehow I missed bonehead's answer. Nevermind.
posted by smcameron at 6:30 PM on January 5, 2011


In the technical sense I use the term, an oxidizer is the thing that steals electrons from the fuel, an "electron donor". These are the standard chemical definitions of oxidizers and reducers, or redox theory. A flame is a plasma state sustained by redox reactions.

In the normal scheme of things, oxygen is the universal electron acceptor for a multitude of fuel electron donors. Gasoline oxidizes to carbon dioxide and water (dihydrogen oxide), sodium metal to sodium oxide and so on.

In this one particular case, the role of oxygen is reversed. In an electrical plasma, oxygen is the electron donor to the only element in the universe which likes electrons more than oxygen does: fluorine. Oxygen really does "burn" in this reaction, by the usual chemical definitions.
posted by bonehead at 6:38 PM on January 5, 2011


Bonehead - wouldn't water be simply "hydrogen oxide"? I thought the mono/di/tri prefixes would be redundant verbiage when all valence shells are bonded full?
posted by -harlequin- at 7:39 PM on January 5, 2011


Not so fast, colleagues.

Molecular oxygen can exist in three forms, monatomic, diatomic (ordinary molecular oxygen), and triatomic (ozone).

A gas composed of monatomic oxygen could be easily ignited would and burn to yield ordinary molecular oxygen and heat. Compressing a quantity of monatomic oxygen would eventually cause it to burn spontaneously without a source of ignition when the pressure got high enough. In such cases, the oxygen would act as its own fuel.

Ozone formation from ordinary O2 is endothermic. Yet because a given mass of ozone exerts less pressure than the same amount of O2 in a given volume, compressing O2 will favor the production of ozone in the compressed gas (an instance of the operation of Le Chatlier's principle). It's conceivable that a bottle of oxygen gas compressed to a sufficiently high pressure would contain enough ozone to essentially 'burn' as the ozone reverted to ordinary oxygen as it was allowed to escape compression.

There are other possibilities involving other combinations of the three forms as well.
posted by jamjam at 8:01 PM on January 5, 2011 [1 favorite]


I'm too tired to remember/look up the IUPAC rules for nomenclature right now, but you may well be right for the formal name -harlequin-. There are many trivial examples of this usage though: carbon dioxide, carbon tetrachloride, silicon dioxide, etc...
posted by bonehead at 8:44 PM on January 5, 2011


The rule about using prefixes in chemical nomenclature is to do it whenever necessary to disambiguate, usually when two non-metals bond, because one or both may have multiple oxidation states. It's not generally necessary when one of the components is a metal of group one or two, which invariably have oxidation states of +1 or +2, respectively. Hydrogen, though, isn't really metallic (except in Jupiter's core?), and sometimes (less frequently) takes a formal oxidation state of -1 (called a hydride, this is why many periodic tables show it above both groups 1 and 7).

So REALLY you'd want to say dihydrogen monoxide. But sometimes a mono- prefix will be omitted and left as understood in the absence of any other prefix, so you could get away with dihydrogen oxide. And since both hydrogen and oxygen do most overwhelmingly have oxidation states of +1 and -2 respectively, you CAN get away with hydrogen oxide. Of course, you could skip the issue by formally treating one of the hydrogens as the +1 and the -OH group as the ion it commonly exists as, giving hydrogen hydroxide. Or invert the charges and get hydroxyl hydride.

In closing, while some fight against DHMO, others who support hydrogen hydroxide claim to have debunked the formers' claims.

I hope the OP will forgive the derail since the actual question has been thoroughly answered.
posted by solotoro at 4:57 AM on January 6, 2011 [1 favorite]


But of course. But don't ask me to understand it! ;-)
posted by St. Alia of the Bunnies at 11:25 AM on January 6, 2011


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