Wikipedia:Reference desk/Archives/Science/2018 September 15

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September 15

Is there something that is non-inflammable 100%?

As I understood everything is flammable (includes rocks and stones as we can see in lava) but all of the materials in the world are kind of located on the scale of flammability and while some require a very low temperature to be flamed and to change form, other materials require a very high temperature (like stones) to be flamed and change form. Is it correct? or there are exception for totally non-inflammable materials? 93.126.116.89 (talk) 05:08, 15 September 2018 (UTC)

Combustion products are essentially non-flammable, such as carbon dioxide, water, etc. but I suppose in principle even those substances can be reacted to higher and higher oxidation states. 139.194.65.208 (talk) 05:14, 15 September 2018 (UTC)

By the way...flammable and inflammable have the same meaning. Non-flammable is the term for something that doesn't burn. 139.194.65.208 (talk) 05:16, 15 September 2018 (UTC)

Thank you, I really didn't know it. I corrected it. 93.126.116.89 (talk) 14:53, 15 September 2018 (UTC)

In principle, CO₂ and H₂O really are completely combusted, with C and H in their maximum possible oxidation states and O happy with a full shell. Trying to oxidise these further would either be completely impossible (H doesn't have any more electrons for anything else to take) or require more energy than any chemical reaction could give (trying to involve the 1s electrons of carbon). Double sharp (talk) 06:15, 15 September 2018 (UTC) (Answer struck based on Ruslik0's comment, raising something which I somehow completely forgot about: this answer is only accurate if we restrict ourselves to combustion in air.) Double sharp (talk) 03:38, 16 September 2018 (UTC)

I get what you are saying but H2O2 Greglocock (talk) 06:34, 15 September 2018 (UTC)

H₂O₂ is thermodynamically unstable and slowly disproportionates to water and oxygen, so it doesn't affect the statement. ^_^ Double sharp (talk) 08:07, 15 September 2018 (UTC)

Of course the H is in the same oxidation state in both water and peroxide, but the oxygen is in the -2 state in water but increases to the -1 state in peroxide. It is further increased to -1/2 in superoxides. 139.194.67.236 (talk) 13:00, 15 September 2018 (UTC)

Yes, but we're typically thinking of oxidising the other element in an oxide, not oxygen itself. Otherwise, we could further oxidise oxygen in all oxides just by decomposing them to their constituent elements. Double sharp (talk) 15:17, 15 September 2018 (UTC)

Water can burn quite well in atmosphere of fluorine. Ruslik_Zero 20:05, 15 September 2018 (UTC)

Hmm, good point. I guess I must have been thinking implicitly of combustion in air. I've struck my original answer and added a note explaining that it only applies to that case. Double sharp (talk) 03:38, 16 September 2018 (UTC)

@Double sharp: What you say is true, in any sane way, yet ... well, in principle, I could take any substance and convert it into a plasma. Then I could take oxygen and convert it to plasma. Then I could mix the two plasmas and they would be intermingled, no matter what, with some conceptual release of energy no matter what, because entropy. Therefore ... everything is combustible at a high enough temperature.  ??? Wnt (talk) 21:51, 15 September 2018 (UTC)

Naturally, we have an article on this - Combustibility and flammability. It appears to confine the definition of flammable to the commonly understood concept of something burning in the presence of oxygen. It lists some non-flammable materials. Interstingly, they include Diesel fuel. Haven't read it all so as to get my head around that yet. HiLo48 (talk) 06:27, 15 September 2018 (UTC)

The article seems to indicate that diesel fuel is considered combustible but not flammable, because it must be heated above room temperature before it ignites. Double sharp (talk) 08:09, 15 September 2018 (UTC)

Just to point out that lava isn't burning, it's molten. Some rocks can be burnt, such as limestone when making quicklime. Although that's strictly thermal decomposition, rather than burning. Mikenorton (talk) 08:54, 15 September 2018 (UTC)

Interesting, but I'd like to know based on what do you say that lava isn't burning while we can see it red and everything that you put into it burn as well.93.126.116.89 (talk) 15:02, 15 September 2018 (UTC)

Melting and burning are not the same thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:34, 15 September 2018 (UTC)

The red/orange glow of lava is black-body radiation. The rock is so hot that it glows in the visible spectrum. This doesn't have anything to do with combustion. --47.146.63.87 (talk) 04:09, 16 September 2018 (UTC)

One obvious example of a rock that burns is coal. 139.194.67.236 (talk) 12:51, 15 September 2018 (UTC)

Coal and jet are rocks that can be set on fire, sometimes with interesting results. --Guy Macon (talk) 13:01, 15 September 2018 (UTC)

Can I conclude from the article that mentioned above above that liquids are the only non-inflammable substance, or there're are also solid materials that no mater what they'll not be burnt? Basically except for water I didn't find a specific solid material that is non-flammable. 93.126.116.89 (talk) 15:00, 15 September 2018 (UTC)

Any oxide is non-flammable. I can think of glass or quartz (SiO2) or corundum (Al2O3). Ruslik_Zero 20:03, 15 September 2018 (UTC)

Tin(II) oxide has a bone to pick with you. That's just one example - conventional burning is still possible for an oxidized material if it can still be oxidized even further by oxygen. Someguy1221 (talk) 03:56, 16 September 2018 (UTC)

Of course, carbon monoxide can also be burned, and is in fact the gas that is combusted in many pyrometallurgical processes. 139.194.67.236 (talk) 10:16, 16 September 2018 (UTC)

In the presence of pure oxygen a lot of unlikely substances can undergo combustion - steel cutting torches depend on this to convert steel to rust, thereby cutting it. Per mention above, there is a difference between temperature-induced incandescence (i.e., fresh lava) and actual combustion. The flames seen coming from lava are from the decomposition of organic material that the lava has covered, which combust. Acroterion (talk) 17:17, 15 September 2018 (UTC)

Funny, non of all the experts, who tried to answer here till now, who obviously have some remarkable deep insight into chemistry and/or physics, mentioned noble gases which are not only 100% "non-inflammable" but even widely used in the industry as Shielding gas (usually Argon) to even prevent any "burning" (aka Exothermic reaction based on Oxygen) from happening. --Kharon (talk) 10:32, 16 September 2018 (UTC)

Except numerous oxides of noble gasses exist such as XeO4. 139.194.67.236 (talk) 13:39, 16 September 2018 (UTC)

XeO4 is manufactured by Synthesis. That hardly counts as inflammable. Whats the other "numerous oxides of noble gasses" that exist according to you? I bet they are all synthetic. With your argumentative pattern you could as well claim that Bricks fly, since you could form them like a wing and add enough air flow to actually make them fly. --Kharon (talk) 14:01, 16 September 2018 (UTC)

Our Noble gas compound article is a good place to start learning about the various classes of compounds of them that exist. For your specific concern about "synthesis", I assume you mean other than simply combining, say, xenon and oxygen at some temperature and pressure and getting xenon oxide? See doi:10.1038/nchem.2528 for examples of exactly that. Given the difficulty in getting it to happen, I suppose it's "combustible" not "flammable", and given the scale on which the reaction is performed, there is presumably not an actual "flame". DMacks (talk) 14:13, 16 September 2018 (UTC)

@DMacks. "Some temperature"? I was actually most impressed that XeO4 explodes above −35.9 °C and started wondering how many hundred Million $ a laboratory probably would cost that would be able to do both, the synthesis and storage, like some casual task for the day.

Btw, have you actually read your source yourself. At least until it mentions "Diamond-anvil-cell experiments" in the second sentence of its description? --Kharon (talk) 21:47, 16 September 2018 (UTC)

Diamond anvil cell experiments are relatively cheap (well, the pair of diamonds are a problem) because they're small scale. This makes them cheap to perform, also safe to perform. The reaction quantities are so small that even energetic results are still manageable. Andy Dingley (talk) 22:09, 16 September 2018 (UTC)

Of course I read the article before writing about it. That's why I clearly stated that the scale was small and the conditions were non-ambient. Even the diamonds of diamond anvils are only a few $K if I recall. And long-term storage of materials only a few tens of °C below zero is trivial too. Dry ice is not expensice even for small amounts to the general public, and large amounts or LN2 or low-temp freezers are present in every even poorly-equipped lab facility I've seen. DMacks (talk) 01:49, 17 September 2018 (UTC)

Indeed, at least the lighter noble gases should really be completely non-inflammable. Helium and neon should qualify under any sane definition since they have no known chemistry; argon should also count, because inserting Ar into an HF molecule isn't oxidising anything. Krypton will react with fluorine, which may count as combustion by some definitions. Double sharp (talk) 01:59, 17 September 2018 (UTC)