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).

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135
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7answers
41k views

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 ...
62
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1answer
8k views

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 ...
46
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6answers
8k views

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 ...
36
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4answers
3k views

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 ...
28
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2answers
6k views

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 ...
26
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1answer
1k views

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. ...
24
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2answers
4k views

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 ...
22
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1answer
8k views

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 ...
19
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1answer
1k views

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 ...
19
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3answers
398 views

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 ...
18
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2answers
3k views

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 ...
16
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3answers
8k views

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 ...
15
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3answers
845 views

What really happens atomically in an explosion?

Let's say a room is filled with butane, I then throw a cigarette into the room. What happens to the atoms/molecules of the butane when they are in contact with the heat from the cigarette?
15
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3answers
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When I burn isopropyl alcohol (IPA), it burns orange. But when I burn ethyl alcohol, it burns totally blue. Why is this?

I burned them in a small aluminium tray. While IPA is burning orange, it produced the smell of soot, but while ethanol is burning blue there isn't any smell. Also, ethanol made the tray really cold ...
14
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5answers
16k views

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, ...
14
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1answer
9k views

Why is there sulfur in black powder / gun powder?

Black powder is composed of charcoal, sulfur and a nitrate salt. The charcoal and sulfur serve as fuel and the nitrate is the oxidizing agent. However, wouldn't it be cheaper to leave out the sulfur, ...
14
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2answers
47k views

Heats of combustion and stability of rings

Which isomer would have the largest heat of combustion? A) Propylcyclopropane B) Ethylcyclobutane C) Methylcyclopentane D) Cyclohexane E) Since they are all isomers, all would have the same heat of ...
14
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1answer
1k views

How can solids undergo combustion if it only occurs in the gas phase?

According to the smoldering Wikipedia article, flaming combustion occurs in the gaseous phase. I know butane undergoes flaming combustion in a Bunsen burner because it's a gas, but how can wood ...
14
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1answer
589 views

Why do some materials turn black and others white after combustion?

Most solids objects turn black after they are burnt. But some turn white. Why is that ?
13
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2answers
35k views

Why is O2 the supporter of combustion?

It's there in every high-school textbook: $\ce{O2}$ is the supporter of combustion. Without $\ce{O2}$ combustion cannot take place. Why? And why only $\ce{O2}$? Why not some other element? And, what ...
12
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2answers
2k views

How does heptafluoropropane suppress fire?

How does heptafluoropropane suppress fire? It says here that it does so by "inhibiting the chain reaction." What does that mean specifically? Does $\ce{O2}$ attach itself to the heptafluoropropane?...
12
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1answer
1k views

Can diamond undergo a self sustaining combustion reaction all the way to carbon dioxide?

I know charcoal can smoulder in an incomplete combustion to produce carbon monoxide so I assume diamond also can. If it's heated to a sufficiently high temperature, will the reaction produce enough ...
12
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1answer
658 views

What are the key chemical characteristics that determine the octane rating of fuel?

The octane rating of petrol (gasoline) is a measure of the how much compression a fuel air mixture can have before detonating (which in petrol engines is a bad thing as you want the mix to combust ...
12
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3answers
8k views

Why is the outermost part of the Bunsen burner flame not the hottest region?

Why is the blue flame the hottest on a Bunsen burner? I thought the outermost part of the flame must be the hottest region because of complete combustion of gases taking place there. Where am I ...
11
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1answer
3k views

What is the difference between ignition temperature and flash point?

I am trying to clarify this for Class 8 Science. Their textbook says "It is the lowest temperature at which a substance catches fire". However, it does not clarify whether it is on its own or due to ...
11
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1answer
13k views

Is combustion considered a redox reaction?

When carbon combusts with oxygen, is this considered a redox reaction since the oxygen atoms gain electrons and the carbon atoms lose them?
10
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4answers
2k views

Would the concentration of oxygen around fire increase as we get close to the fire (from the outside)

Since fire require oxygen, wouldn't a fire, like those in the American forest along west coast, constantly draws in oxygen from around? And if that is so, would the concentration of oxygen around the ...
10
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3answers
47k views

CH4 + O2 => CO2 + 2H2, what's wrong with it?

It says in my textbook that: $$\ce{CH4 + 2 O2 -> CO2 + 2 H2O}$$ which seems like a displacement reaction to me. Shouldn't the reaction be: $$\ce{CH4 + O2 -> CO2 + 2 H2}$$ since $\ce{4H}$ ...
10
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2answers
205 views

Carbon tetraradical

I was just reading through Reactions: The private life of atoms by Peter Atkins and I noticed that in Chapter 3, the chapter on the combustion reaction, the author writes: As we watch we see $\ce {...
10
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1answer
327 views

Gases produced by pyrolysis of cellulose

I heated cotton in a sealed container (with a small hole) over a natural gas flame. Some gases and smoke were produced. What would they probably be? I can come up with some guesses based on the ...
10
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3answers
409 views

Why does internal combustion engine smoke appear blue? Could there be “blue molecules” in it?

Four-stroke and two-stroke gasoline engines as well as diesel engines can all emit dense clouds of blue-tinged smoke under various transient loads or incorrectly tuned conditions. Raleigh scattering -...
10
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1answer
3k views

What is the oxidation mechanism of gunpowder?

I've been recently looking into fireworks and the chemistry of explosives, and I found out that, amongst others, one of the most important reactions in gunpowder ignition is the oxidation of charcoal ...
10
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1answer
5k views

Can class D fire extinguishers be used for other fire types than metal fires?

Burning metals like sodium should not be extinguished with standard fire extinguishers, but they require either sand or a special class D fire extinguisher. Now, if there is a fire in the lab and ...
9
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4answers
1k views

On heating in the Earth's atmosphere, can magnesium react with nitrogen to form magnesium nitride?

This question is derived from a question asked in my school test. What happens when a magnesium ribbon is heated in air? My first response was the formation of magnesium oxide $(\ce{MgO})$ when ...
9
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5answers
1k views

Can paper burn without oxygen or air?

If you put a paper inside an oven vacuum packed and go beyond $250~\mathrm{^\circ C}$, will it burn? There's no oxidizer. If not, what will happen?
9
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1answer
7k views

Why do gummy bears explode when added to hot potassium chlorate?

This link shows that a gummy bear explodes when in contact with heated potassium chlorate, $\ce{KClO3}$. But what in a gummy bear creates this reaction? Also, do other foods (fruit, icing sugar...) ...
9
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1answer
413 views

Forms of carbon in incomplete combustion

When hydrocarbons burn with little oxygen, carbon is produced. What form do these particulates of carbon come in? Is it a simple molecule like $\ce{S8}$, or a small fragment of a larger structure, ...
9
votes
1answer
586 views

Is the flame temperature of a burning fuel affected by pre-heating the fuel?

This page on Adiabatic temperatures helpfully lists the theoretical maximum temperatures that flames will reach under certain conditions for a number of fuels. They assume initial atmospheric ...
9
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1answer
167 views

In a Koppers-Totzek reactor, why do I get CO and H₂ instead of CO₂ and H₂O?

A Koppers-Totzek reactor (there seems to be only a German Wikipedia page) is an entrained flow gasifier that blows coal dust, oxygen and water (as steam, of course) into a burning chamber where the ...
8
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7answers
4k views

Examples of non-volatile, but flammable liquids?

As far as I know, most flammable liquids are volatile. Are there flammable liquids that are non-volatile?
8
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2answers
3k views

Why is oxygen so special?

Why do reactions with oxygen produce flame (i.e. light), heat and hence a lot of energy? I mean, why only oxygen, why not any other element like nitrogen? What is special about the electronic ...
8
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2answers
110k views

What are the differences between diesel and unleaded gasoline?

I am curious about the flammability of diesel fuel and its properties, as I don't deal with it on a regular basis (at all). In particular, I want to know how the fuel works when powering a diesel ...
8
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2answers
20k views

Is it possible to light a match by scratching it on hard surfaces, like they do in movies?

In movies cool guys don't need a matchbox − they just light a match by scratching it on whatever hard surface − concrete walls, wooden bar tables, leather belts, etc. Is it just a movie trick, or is ...
8
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2answers
679 views

How is octane rating defined for negative values and those over 100?

Based on my reading, the octane rating for a given fuel is calculated by finding the compression ratio at which it knocks and finding a mixture of $X\%$ isooctane and $(100 - X)\%$ n-heptane which ...
8
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3answers
15k views

Can you melt wood?

We talked about it in our chemistry class but we couldn't get to a conclusion, any help?
8
votes
2answers
827 views

Could blue flames arise within the hull of a burning ship?

In Joseph Conrad's Youth: A Narrative, set in 1876, a 400-ton barque ship, the Judea, is sent to Java Head to transport 600 tons of coal. Although various delays occur during its journey, the coal it ...
8
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2answers
279 views

How is this mystery chemical reducing carbon emissions?

My chemistry is not good enough to solve this problem, and it's driving me crazy. At my job, a sales agent approached me to be their representative in my area for their product. It's a product that ...
8
votes
3answers
782 views

How is combustion speed regulated in solid propellants?

My question on Space.SE didn't yield anything I didn't know already: the secondary regulation mechanism – grain (cross-section shape) of the propellant, changing the area of open surface of the ...
8
votes
1answer
326 views

Based on their respective number of degrees of freedom, what's the most efficient fuel; hydrogen or gasoline?

The reaction of octane's combustion is: $$\ce{2 C8H18 + 25 O2 -> 18 H2O + 16 CO2}$$ I am asked for computing the number of degrees of freedom of the octane given that its specific heat is $\pu{...
8
votes
1answer
754 views

What chemical can cause such a fire? [closed]

A friend of mine who thinks that she is under influence of black magic met an astrologer. The astrologer asked her to wear a t-shirt for three nights and then bring that to him. The astrologer then ...

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