Talk:Fire

Fire in curved space

Most of reality is nearly flat, the tallest mountain far less than a millimeter above the lowest valley. When I think of fire, I imagine an earthquake of our world falling down a large fault line, a few quanta tall as some atoms come apart (up direction) and fall together (down direction) farther in other combinations, and the quake is felt as light, which is the curve of space, echos outward in many directions like a tidal wave, pushing up the nearly flat surface of reality wherever it may hit and everywhere between.

Everywhere and everything is Event_horizon not just the most extreme parts where we normally think of blackholes.

Fire is Photoelectric_effect extended to molecules instead of just electrons, similar to a nuclear explosion emitting light except it doesnt fall that far.

not in citation, etc

" Fire also kept nocturnal predators at bay. Evidence of cooked food is found from 1.9 million years ago,[19]" <<< The cited source do not have this string "1.9" the closest date is "The basalt member at the base of the Chesowanja Formation has been dated to 1.42±0.07 Ma," and it was site with bones of Australopithecus boisei. Also not only nocturnal predators fire keep at bay; diurnal predators too.

This girl tried to insert propaganda on this page

This girl tried to insert propaganda on this page. She's a well-known fire apologist and will try to skew the page. https://www.sandraandwoo.com/2021/04/13/1260-larisas-life-advice-part-1/ Teolemon (talk) 06:31, 21 April 2021 (UTC)

Semi-protected edit request on 7 January 2022

The fourth picture is mislabeled as “ coal” when it should say “charcoal”. Bstormo (talk) 02:07, 7 January 2022 (UTC)

 Done ––FormalDude ^talk 03:41, 7 January 2022 (UTC)

Fringe theories

I'd like to remove this sentence from the lede:

Fire is hot because the conversion of the weak double bond in molecular oxygen, O₂, to the stronger bonds in the combustion products carbon dioxide and water releases energy (418 kJ per 32 g of O₂); the bond energies of the fuel play only a minor role here.

The statements are part of a fringe theory which the author calls "the oxygen theory of combustion and respiration energetics". While not all of the claims in the quoted sentence are incorrect, the suggestion that energy is "stored in" oxygen rather than the fuel certainly is, and the estimate of 418 kJ/mol(O₂) for the heat of combustion is "valid" only for a small class of fuels. The remaining statements do not seem important enough to me to remain in the article's lede.

Please note that the editor in question has added references to his papers to a large number of Wikipedia articles, usually to support pseudoscience claims. Removing them all is going to take a while.

IpseCustos (talk) 09:40, 10 June 2022 (UTC)

This sentence is a correct and relevant scientific statement about bond energies and the heat of combustion, not a suggestion or opinion. It states documented, verifiable facts based on universally accepted values of bond energies. That heats of reaction, including combustion, can be estimated from bond energies is also universally accepted in chemistry. A peer-reviewed reference providing all the details is provided for verification. In short, nothing is scientifically incorrect about this sentence.

The claim that the estimate of 418 kJ/mol(O₂) is valid "only for a small class of fuels" is very misleading. The estimate for the heat of combustion is valid (±3%) for most common organic fuels and millions of other organic molecules. Only if the fuel contains triple bonds or more heteroatoms (O, N, S, P) than carbon atoms, which is fairly uncommon, does the estimate become less accurate (usually ±30%), but this is still useful.

Editors are of course free to replace this sentence with a better, even more widely applicable and more accurate explanation (properly sourced) of the heat released by fire. But just deleting this correct explanation of a central property of fire, namely that it is hot, is not in the interest of Wikipedia readers.

Klaus Schmidt-Rohr (talk) 14:22, 10 June 2022 (UTC)

"Common organic fuel without triple bonds and with few heteroatoms" is a highly restricted class. Still, benzene falls outside of your range, for example, because aromaticity is one of the many factors you're not accounting for.

But that doesn't matter. Incorrect claims are fine on Wikipedia as long as they're referenced by verifiable, reliable (ideally, secondary) sources which establish their notability.

Please provide such sources.

IpseCustos (talk) 17:50, 10 June 2022 (UTC)

The condition is not "with few heteroatoms"; for instance, sugars contain as many heteroatoms as carbon atoms, and the estimate applies very well. When heteroatoms exceed carbon atoms, which is fairly uncommon, then the heat of combustion may be somewhat larger (because of weak bonds among the heteroatoms). Notably, the reaction is still highly exothermic because of weakly bonded atoms other than C and H in the reactants. And there is no restriction to common organic fuels; it applies to any organic molecule not dominated by heteroatoms, and the larger and more complex the molecule, the smaller the percent error. So this is not a highly restrictive class.

Benzene does not fall outside my range. The estimate of the standard heat of combustion (i.e. the higher heating value) gives -418 kJ/mol (6+6x0.3)= -3260 kJ/mol; the experimental value from NIST is -3268 kJ/mol. That's a deviation of only 0.2% (comparable to the experimental uncertainty). The over 500 molecules for which the standard deviation of <3% was determined contain a large number of examples with aromatic rings. So my claim is not incorrect, at all.

When a Wikipedia article discusses a scientific question, provably incorrect claims should not be acceptable if there are sources that make provably correct statements on the topic. When it comes to science, a source that makes an incorrect claim is not "reliable" on that topic, by definition. If there is no reliable secondary source, then primary sources must be acceptable. Otherwise, you would be saying that primary sources can never be quoted on Wikipedia, which is not true. It seems that there is no secondary source that explains why fire it hot and the heat of combustion proportional to oxygen consumption (please prove this conclusion wrong to end this discussion), so we must resort to peer-reviewed primary sources from reputable publishers like the American Chemical Society; that is consistent with Wikipedia rules.

In addition, ANSI and ISO standards have now been added as sources to a central statement in this paragraph. These will count as secondary sources. Klaus Schmidt-Rohr (talk) 02:42, 12 June 2022 (UTC)

You're confusing two different methods of estimation. The one we were talking about in this article is "-419 kJ/mol(O₂)", which results in a number of -3142 kJ/mol for benzene.

The reason there are no good secondary sources that give a positive answer to your question is because the negative answer is well-established. That's not a good reason to go looking for primary sources that slipped through some kind of peer-review process and give a positive answer. It's a good reason not to include the positive answer as fact. IpseCustos (talk) 07:06, 12 June 2022 (UTC)

You are confusing the lower and higher heating values of benzene. The formula you used, which does not include the heat released by condensation of water, gives the lower heating value of benzene. The experimental value of the lower heating value of benzene is -3136 kJ/mol, in excellent agreement (<0.2% deviation) with the estimate of -3142 kJ/mol from -419 kJ/mol(O₂). This confirms again that this simple formula provides very good estimates of heats of combustion of organic fuels.

To address the concerns raised, I have revised the sentence that is under debate here. Please have a look. Every statement made is now documented by a reliable secondary source (a textbook with a specific page number or an official standard). I hope that will settle the issue. Klaus Schmidt-Rohr (talk) 13:39, 12 June 2022 (UTC)

It is not clear to me from the text of the article that the "-419 kJ/mol(O₂)" method refers to the lower heating value. If it does, please make that clear in the article so others won't look as silly as I do now. (In other words, you're right about benzene, we need to look further than mere aromaticity for significant differences).

Regardless, we need to point out clearly that this method yields a usable but rough estimate (why the three-digit precision, then?), not a precise value, for a restricted class of fuels (dry ones, in particular). And that makes the statement too long and specific to go in the lede section of an article about fire.

My suggestion remains to move this sentence to the "Chemistry" section.

(Do you happen to have at hand the numbers for triacetone triperoxide? Maybe "peroxides" is another exception to your rule...)

Once we have a specific statement about a specific class of fuels and a reasonable statement that this is an approximation, not a precise calculation, we can look for references and include the statement in the chemistry section, IMHO. IpseCustos (talk) 14:28, 12 June 2022 (UTC)

By changing the crucial phrase to "(about 420 kJ per 32 g of O₂, for most dry organic fuels)", I have addressed all the points of criticism:

-- "about 420" has only two significant figures and is explicitly approximate.

-- "dry" specifies that the fuel must be dry.

-- "most" does not claim all fuels. Still one should note that this is such a useful value that it is used widely in fire safety practice and is part of official standards, as quoted.

-- it's not a very long phrase.

The lower heating value is implied here because this is an article about fire, not about the standard heat of combustion measured in a calorimeter cooled back to 298 K. Because fire is hot, most water formed does not condense to give off its heat at the site of the fire. Lower and higher heating values are appropriately discussed under Heat of combustion. Klaus Schmidt-Rohr (talk) 01:20, 13 June 2022 (UTC)

References

Without expressing an opinion here (because I lack one) I at least observe the sentence was added a few years ago in this DIFF by Klaus Schmidt-Rohr (talk · contribs), who indeed appears to be the cited paper's author. NewsAndEventsGuy (talk) 13:49, 10 June 2022 (UTC)