Questions tagged [combustion]

For questions about the combustion of an organic molecule or inorganic substance. Do not use this tag if your question is about the [stoichiometry] of a combustion reaction, or for the calculations of [thermodynamics] functions (like enthalpy change).

It is an exothermic process by which a substance is oxidized (by an oxidizing agent such as oxygen) to release a large amount of energy in the form of heat and often light.

Combustion is a reaction with complicated radical chain mechanisms, depending on substrates - combustible substance and oxidiser.

Combustible materials include most of the organic compounds (for example petrol and ethanol) and many inorganic ones (like ammonia and boranes), as also many elementary substances, like carbon, sulfur or more reactive metals.

Oxygen is most popular oxidizer for combustion, but also chlorine, fluorine, and compounds of these elements can be used.

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Why doesn't water burn?

Hydrogen is flammable, and for any fire to burn it needs oxygen. Why does a compound made of hydrogen and oxygen put out fires instead of catalyzing them? I understand that hydrogen and water are chemically different compounds, but what causes water…
Prageeth Saravanan
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Why does shaking a match put the fire out?

Move a match slowly and nothing happens but if you shake it violently the fire will extinguish. Oxygen makes fire grow so why does waving a flame through the oxygen rich air put the fire out? Does this primarily have to do with a decrease in…
carb0nshel1
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Why does wood burn but not sugar?

Fundamentally, they're both carbohydrates, although the cellulose in wood is essentially polymerized glucose, which combined with its isomer fructose forms sucrose. So why does wood readily burn while table sugar chars?
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Does any known substance ignite on cooling?

As the title says, I'm interested in knowing if there is any substance — or combination of substances — that ignites (or even increases its chance of spontaneous ignition) when cooled. I've never heard of such a thing, nor can I find it in Atkins'…
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Why do the alkali metals form different products upon combustion in air?

From Wikipedia's article on sodium: When burned in dry air, it forms primarily sodium peroxide with some sodium oxide. We know that sodium has a strong reducing capacity, so why does it produce a compound in which the oxygen atom is not reduced to…
CowperKettle
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When a candle burns, why does the top of wick glow if bottom of flame is hottest?

Totally an elementary question. Staring at a candle, it appears that the bottom of the wick is dark whereas the top glows. However the bottom of the flame (the blue) is the hottest. Is the reason for this that the concentration of liquid wax is…
ZAR
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What single, pure compound would best replace petrol?

Petrol for use as automotive fuel is produced by blending of different product streams of oil refining. It consists of hundreds of different compounds, and the exact composition can vary widely. Certainly, not all components are absolutely…
user7951
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What is behind of the attraction between a burned matchstick with a magnet?

I do not know how to understand the reasons of why a burned matchstick is attracted by a magnet (most probably) of Neodymium. Here are some screenshots of a video in which this natural phenomenon is presented: (In the video, see at 1 min 25…
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Open flame combustion in bizarro world

Humans typically achieve combustion by starting a chemical reaction of a fuel (often a carbon $\ce{C}$ containing fluid like methane $\ce{CH4}$), which is is brought into an an oxidizer (a gas containing $\ce{O}$, like air). For example, when you…
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How do self-relighting (trick) birthday candles work?

You may have seen those birthday candles, where, upon blowing them out they smoulder for a bit and then (magically) relight. How do they work? Why can't regular candles do this (is it possible for a regular candle to relight itself, anyway?)
Melanie Shebel
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How can titanium burn in nitrogen?

I was going through the properties of titanium when a certain thing caught my eye: It was the reaction of burning of titanium in nitrogen. I was astonished to read it as I knew that neither is nitrogen a supporter of combustion nor does it burn…
Abhi
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What is going on in and below a yellow or blue gas flame?

Unsure if this is more chemistry or physics, but here goes... Consider a Bunsen burner and the flame it produces when the air inlets are closed vs open. According to the description on the linked Wikipedia page, combustion is incomplete when the air…
Anthony X
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Is there a point at which Ethanol (E10) fuel becomes harmful to gas tanks or engines if not used?

This is not the typical chemistry question on this website, but I think it's an important practical question. When I got a gas string trimmer, the woman who worked at the gardening shop told me that E10 (fuel commonly sold in the USA - 10% Ethanol,…
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Why doesn't NASA or SpaceX use ozone as an oxidizer for rocket fuels?

Presumably, it would be expensive to use ozone ($\ce{O3}$) as an oxidizer instead of $\ce{O2}$, but would the extra oomph be worth it? Does $\ce{O2}$ provide as much thrust/energy/heat as can be provided, given the liquid hydrogen propellant? I…
Kurt Hikes
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Can flames be colored black?

Most of us here would know that flames can be colored by adding an appropriate salt to the 'fuel' or by simply introducing it into a flame. Boron and Barium salts give the flame a green tinge, Strontium colors it red, Sodium does gold, copper a…
paracetamol
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