Editing Flame (section)

==Mechanism==
[[File:Anatomy of a candle flame.svg|thumb|Zones in a candle flame<br>The interior of the luminous zone can be much hotter, beyond {{cvt|1500|C|F}}.<ref>{{Cite journal |last1=Zheng |first1=Shu |last2=Ni |first2=Li |last3=Liu |first3=Huawei |last4=Zhou |first4=Huaichun |date=2019-04-01 |title=Measurement of the distribution of temperature and emissivity of a candle flame using hyperspectral imaging technique |url=https://www.sciencedirect.com/science/article/pii/S0030402619301949 |journal=Optik |language=en |volume=183 |pages=222–231 |doi=10.1016/j.ijleo.2019.02.077 |bibcode=|s2cid=126553613 |issn=0030-4026|url-access=subscription }}</ref>]]
Color and temperature of a flame are dependent on the type of fuel involved in the combustion. For example, when a lighter is held to a [[candle]], the applied heat causes the fuel molecules in the [[Paraffin wax|candle wax]] to vaporize.{{notetag|If this process happens in an inert atmosphere without [[oxidizer]], it is called {{em|[[pyrolysis]]}}.}} In this state they can then readily react with [[oxygen]] in the air, which gives off enough heat in the subsequent exothermic reaction to vaporize yet more fuel, thus sustaining a consistent flame. The high temperature of the flame causes the vaporized fuel molecules to [[Chemical decomposition|decompose]], forming various incomplete combustion products and [[radical (chemistry)|free radicals]], and these products then react with each other and with the [[Oxidizing agent|oxidizer]] involved in the reaction of the following flame (fire).

One may investigate different parts of a candle flame with the aid of a cold metal spoon:<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211211/tMDKeBaLWDw Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20150804032938/https://www.youtube.com/watch?v=tMDKeBaLWDw Wayback Machine]{{cbignore}}: {{cite web|title=What Is Fire?| website=[[YouTube]] | date=3 August 2015 |url=https://www.youtube.com/watch?v=tMDKeBaLWDw|language=en|access-date=2019-11-27}}{{cbignore}}</ref> the higher parts of the flame produce water vapor deposition, the result of combustion, the yellow parts in the middle produce [[soot]], and the area near the candle wick produces unburned wax. Goldsmiths use higher parts of a flame with a metallic blow-pipe for melting gold and silver. Sufficient energy in the flame will excite the electrons in some of the transient reaction intermediates such as the [[methylidyne radical]] (CH) and [[diatomic carbon]] (C<sub>2</sub>), which results in the emission of visible light as these substances release their excess energy (see spectrum below for an explanation of which specific radical species produce which specific colors). As the combustion temperature of a flame increases (if the flame contains small particles of unburnt carbon or other material), so does the average energy of the electromagnetic radiation given off by the flame (see [[Black body]]).

Other oxidizers besides oxygen can be used to produce a flame. Hydrogen burning in chlorine produces a flame and in the process emits gaseous [[hydrogen chloride]] (HCl) as the combustion product.<ref>{{cite web|url=http://genchem.chem.wisc.edu/demonstrations/Inorganic/pages/Group67/chlorine_and_hydrogen.htm|archive-url=https://web.archive.org/web/20080820080559/http://genchem.chem.wisc.edu/demonstrations/Inorganic/pages/Group67/chlorine_and_hydrogen.htm|archive-date=2008-08-20|title=Reaction of Chlorine with Hydrogen}}</ref> Another of many possible chemical combinations is [[hydrazine]] and [[nitrogen tetroxide]] which is [[hypergolic]] and commonly used in rocket engines. [[Fluoropolymer]]s can be used to supply [[fluorine]] as an oxidizer of metallic fuels, e.g. in the [[magnesium/teflon/viton]] composition.

The [[chemical kinetics]] occurring in the flame are very complex and typically involve a large number of chemical reactions and intermediate species, most of them [[radical (chemistry)|radicals]]. For instance, a well-known chemical kinetics scheme, GRI-Mech,<ref>{{cite web |author1=Gregory P. Smith |author2=David M. Golden |author3=Michael Frenklach |author4=Nigel W. Moriarty |author5=Boris Eiteneer |author6=Mikhail Goldenberg |author7=C. Thomas Bowman |author8=Ronald K. Hanson |author9=Soonho Song |author10=William C. Gardiner Jr. |author11=Vitali V. Lissianski |author12=Zhiwei Qin |title=GRI-Mech 3.0 |url=http://www.me.berkeley.edu/gri_mech/ |url-status=dead |archive-url=https://web.archive.org/web/20071029194024/http://www.me.berkeley.edu/gri_mech/ |archive-date=29 October 2007|access-date=8 November 2007 }}</ref> uses 53 species and 325 elementary reactions to describe combustion of [[biogas]].

There are different methods of distributing the required components of combustion to a flame. In a [[diffusion flame]], oxygen and fuel diffuse into each other; the flame occurs where they meet. In a [[premixed flame]], the oxygen and fuel are premixed beforehand, which results in a different type of flame. Candle flames (a diffusion flame) operate through evaporation of the fuel which rises in a [[laminar flow]] of hot gas which then mixes with surrounding oxygen and combusts.