Science Questions

What is the composition of fire?

Sun, 27th Jul 2008

Listen Now    Download as mp3 from the show Naked Science Questions and Answers

Question

Guillermo Davies Ore asked:

What is the composition of fire?

Answer

Chris -  Fire looks like a solid thing but itís not. Itís actually just vapour. When you heat something up to a high temperature it shoves out chemicals which are volatile and flammable. They mix with oxygen which is coming from the air around them. They combust so they react with the oxygen and they burn releasing heat. They also produce some degradation products or burning products from combustion. When you make that it glows. Itís incandescent and it gives out light at different wavelengths and different chemicals make different coloured lights. Thatís why flames have different colours. Sodiumís very common and that makes flames an orange colour. If you have incomplete combustion. If you have some sooty particles in the smoke or the vapour theyíll glow orange as well. This is why you then see this orange pattern.

Multimedia

Subscribe Free

Related Content

Comments

Make a comment

Guillermo Davies asked the Naked Scientists: Is fire any kind of matter? If so, which state of matter is it in, plasma, gas? What do you think? Guillermo Davies, Sun, 27th Jul 2008

Fire is more of a 'process' than a substance, I should say.
The 'matter' in a fire is the fuel and the Oxygen (plus Nitrogen, etc, which play no real part).
The oxidation process is very rapid (and exothermal) which raises the temperature and  provides the activation energy to continue the process.
A plasma consists of a mixture of ions which are separated by virtue of the average thermal energy (i.e. temperature) being greater than the potential energy of attraction between the ions. There may be some flames where this happens but I don't think the temperature is high enough in 'yer average' candle flame.
Aren't the fuels and the oxides covalent compounds so the energy would only be available if they actually combined?
Go on, BC - put me right. I promise not to get abusive! lyner, Sun, 27th Jul 2008

Technically a plasma is any ionised gas (subject to being shouted at by physicists) so a candle flame is a dilute plasma. A decent meter will let you demonstrate that a candle flame conducts electricity. Not many of the molecules get ionised, but some do.

Anyway, describing fire as a process rather than a material sums it up rather well.
Bored chemist, Wed, 30th Jul 2008

Why do you hate me so?
You are always putting me right (gnaws knuckles and kicks the cat).


I should have remembered the 'flame probe' for detecting high voltage potentials. lyner, Thu, 31st Jul 2008

Of course, I love you dearly. But my love of scientific truth tends to win out. Bored chemist, Thu, 31st Jul 2008

] lightarrow, Fri, 1st Aug 2008

That's true - particularly around the outside. lyner, Fri, 1st Aug 2008

Why are you fighting? Someone tell what actually is fire. Does it have mass? Can it be made to occupy fixed shape? Why does it flutter? Why is it pointed at top? If it is a reaction, what are the reactants and products? If it were a process, I believe it shouldn't have been such a physical thing which could be seen. If it is a matter, it should be within three states. And Mr. Plasma, I request you to clear your concept as Mr. Process did. Pramod Kandel, Sun, 31st Jan 2010

Fire is the physical manifestation of an incorporeal reality or the spirit of Yahweh. That is the reason it can't be defined under matter as the other elements are and there has to be three (3) conditions in order to invoke fire. This is showing that the creator Yahweh is a 3-fold unity being the Father, The Word and Holy Spirit. At no point in time will you get Yahweh without the 3-fold unity just like there can't be fire without those 3 conditions present which are the fuel, oxygen and heat. Anthony Williams \"Bocetti\", Fri, 5th Mar 2010



Amen to that.. So fire proves there is indeed God, and therefore disproves other theories such as the big bang, the evolution and so on. Dr. Junix, Wed, 29th Jun 2011

http://www.youtube.com/watch?v=Oc4D3m05Hes&playnext=1&list=PL512787F5D8869660 Mr. Data, Wed, 29th Jun 2011


Amen to that.. So fire proves there is indeed God, and therefore disproves other theories such as the big bang, the evolution and so on.

I am not sure you could conclude that fire proves God.

However, if you think of Traditional Chinese Balance (Medicine?), there are five basic elements:

Fire, Wood, Earth, Water, and Metal.

http://healthy-ojas.com/systems/tcm-five-elements.html

I can't really say much about the theory, but:
CliffordK, Wed, 29th Jun 2011

Let's keep it Science please guys!  imatfaal, Wed, 29th Jun 2011


Amen to that.. So fire proves there is indeed God, and therefore disproves other theories such as the big bang, the evolution and so on.

I am not sure you could conclude that fire proves God.

However, if you think of Traditional Chinese Balance (Medicine?), there are five basic elements:

Fire, Wood, Earth, Water, and Metal.

http://healthy-ojas.com/systems/tcm-five-elements.html

I can't really say much about the theory, but:



Yes... the link I gave gives a very accurate description of such myths. Mr. Data, Wed, 29th Jun 2011



Fire is just infrared light. Mr. Data, Wed, 29th Jun 2011



Fire is just infrared light.


No. fire is a process in which combustible materials form a hot gas/weakly ionised plasma imatfaal, Wed, 29th Jun 2011



Fire is just infrared light.


No. fire is a process in which combustible materials form a hot gas/weakly ionised plasma


what do you think this combustable material emmits? wiki states:

''Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products''

Now ask what infrared light is.

''We experience infrared light every time we feel the heat of the sun on our skin or the warmth of a camp fire.''

http://astro.uchicago.edu/cara/about_cara/defn/irlight.html

I know my data. Mr. Data, Wed, 29th Jun 2011

Sorry - it's fairly simple; Fire is not just infrared light. (fire gives off infrared amongst other things). You might want to google convection, conduction and radiation as heat transfer methods.  On the campfire example - this is one of the reasons it is much hotter downwind of a campfire than upwind. imatfaal, Wed, 29th Jun 2011

You:

''Sorry - it's fairly simple; Fire is not just infrared light.''

Me: pre:

''fire is just infrared light''

You:

''No. fire is a process in which combustible materials form a hot gas/weakly ionised plasma.''

Make up your mind please. Mr. Data, Wed, 29th Jun 2011

ch4 + o2= co2 + h2o. @ the = sign the flame exists. Is there a difference in the mass on the left side of the = sign from the right side ?  ASSUME THE EQUATION IS PROPERLY BALANCED,sorry. CZARCAR, Wed, 29th Jun 2011



Yes... combustion. If my chemistry suits me well, ch4 is the greenhouse gas... a temperature effect on objects, o2 is the oxygen. As you will notice, these are not fundamental effects. They are atomic. If you want to know the fundamental effects, you ask what fire is made of, and in it's most simplest terms, it is an infrared light, as I have explained. And proved. Mr. Data, Wed, 29th Jun 2011

In fact, o2 is a molecular construction is it not? We need the fundamental answer, which I have given. Atomic was not even close, and molecular physics is even further from the fundamental answer. Mr. Data, Wed, 29th Jun 2011

The most familiar form of fire -- orange, yellow, or white flame -- is due to orange, yellow, or white hot sooty particles. It is a solid aerosol, and not really a gas or a plasma.

Blue flame is due to emission of light from several types of diatomic molecule that are formed in the combustion reaction in excited states -- things like C2, CN, CH, and OH. It involves high energy and unfamiliar molecules, but usually not ions as such.

The presence of trace quantities of metals which easily form ions often leads to characteristic colours of flame: potassium gives lilac flame, barium or copper give green, lithium, calcium or strontium give red. But the one that usually dominates is sodium, which seems to get everywhere, and produces a slightly orange yellow colour in a flame -- the same colour as sodium street lights.

You can tell the difference between these different types of flame very easily with a simple pocket spectroscope. Solid aerosols will show a continuous spectrum; typical flame diatomics a banded spectrum, and metal ions will produce sharp spectral lines. damocles, Wed, 29th Jun 2011



Gas... plasma... still an infrared energy... I don't understand if you are either challenging the debate, or giving your penny in? Mr. Data, Wed, 29th Jun 2011



OK. 'Twas originally intended as just putting my penny in. The original subject referred to the "composition" of fire, which would normally be a reference to any material content rather than radiation output.

But I will rise to the challenge.

Much of the radiative output isn't infrared energy, though some of it is. But the fact that (most) flames are visible means that fire typically involves visible as well as infrared light energy output. damocles, Wed, 29th Jun 2011

It says someone has posted.... I don't see this poster's post? Mr. Data, Wed, 29th Jun 2011

Mr Data,
Could you stop talking bollocks please?
Imatfall is perfectly correct. Fire is a process.
That process happens to give out IR, but I also give out IR- yet I am not a fire.
Your assertion that "Fire is just infrared light." is plainly wrong.
Re.
"If my chemistry suits me well, ch4 is the greenhouse gas"
The greenhouse gas effect is physics not chemistry.

"They are atomic."
While there are generally free atoms in flames, they are a long way from the whole story. In fact a flame composed entirely of atoms is not possible, so they are hardly fundamental to the issue of what a fire is.

you say "you ask what fire is made of, and in it's most simplest terms, it is an infrared light, as I have explained. And proved." when you have proved nothing of the sort.

If you carry on in this way you will probably get banned from the site for trolling.
Bored chemist, Wed, 29th Jun 2011

I am not talking bollocks. I admitted fire was a process, but I proclaimed the state of matter was of infrared-type: This is what was questioned, and now I am threatened by another member without all the relevent facts. Well, let us leave it at then. I know when I am not welcome.... (even though I contributed to the physics)! Mr. Data, Wed, 29th Jun 2011



Mr Data,

I don't think Bored Chemist threatened you at all, but he did give you very sound advice. Geezer, Wed, 29th Jun 2011

well then how do you explain St. Elmo's Fire? It doesn't have the process of combustion as you say.

Also, I think lightning or electricity can be associated or identified as fire. Dr. Junix, Thu, 30th Jun 2011

" I proclaimed the state of matter was of infrared-type"
For a start, that's a lie. You claimed "Fire is just infrared light".
Also it makes no sense since infra red isn't a type of state of matter. That#s talking bollocks again.
And then you said you had been threatened.
Well, by whom?
I don't have the power to ban you.
So your talk of a threat is more bollocks.
Would you please stop it.


Bored chemist, Thu, 30th Jun 2011

i think, fire has no absolute chemical composition just like electricity. to create fire, you do not need to follow some chemical rules like creating water which you can easily say as H2O.

And as for my saying that electricity could be associated or identified as fire is that they both share the same characteristics meaning they both burn, generate heat and generate light! It is probably the only element that is in its purest form.

Dr. Junix, Thu, 30th Jun 2011



St Elmo's fire does produce light in a very similar manner to non-sooty flames.  The coronal discharge in an electic field creates a small amount of ionisation of the air around the sharp tip of a grounded conductor.  This very weakly ionised plasma/gas glows with the characteristic spookly blueish white light of st elmos fire - which I must admit that, even when you understand the process, is still disconcerting when you first see it. imatfaal, Thu, 30th Jun 2011


I explain it by pointing out that, just because something has the word "fire" in the name doesn't mean it's really fire.
http://www.youtube.com/watch?v=mjxdmsXzwmQ Bored chemist, Thu, 30th Jun 2011

nice link Bored Chemist.. but your youtube link doesn't explain in detail how fire works...nice dancing though... Dr. Junix, Thu, 7th Jul 2011



Yes... combustion. If my chemistry suits me well, ch4 is the greenhouse gas... a temperature effect on objects, o2 is the oxygen. As you will notice, these are not fundamental effects. They are atomic. If you want to know the fundamental effects, you ask what fire is made of, and in it's most simplest terms, it is an infrared light, as I have explained. And proved.
So if we weigh the fuel be4 the burn & the gasses after the burn they would be equal & the only definition for the flame would be massless infrared?
CZARCAR, Thu, 7th Jul 2011



Yes... combustion. If my chemistry suits me well, ch4 is the greenhouse gas... a temperature effect on objects, o2 is the oxygen. As you will notice, these are not fundamental effects. They are atomic. If you want to know the fundamental effects, you ask what fire is made of, and in it's most simplest terms, it is an infrared light, as I have explained. And proved.
So if we weigh the fuel be4 the burn & the gasses after the burn they would be equal & the only definition for the flame would be massless infrared?


No, because Mr Data is wrong. His is a silly definition. Bored chemist, Fri, 8th Jul 2011

What is fire made of....?  Fire as you see it (energy in the form of light)? Or, what is comprised resulting in fire?  4 components are required for fire to exist (together)...... heat, fuel, oxygen (air), and a chemical chain reaction. In that order...... It was formerly known as the fire triangle, but fire tetrahedron is the proper term as the fourth element being the chain reaction is what enables, and sustains fire buy maintaining heat which seperates gasses from the fuel source and so on. mlarsen77, Fri, 8th Jul 2011

I do not have a degree......didnt even finish college......but I know fire is not made of light...... Light is a form of energy released by the chemical chain reaction. mlarsen77, Fri, 8th Jul 2011

What is the composition of fire?

I think we have taken the discussion into the wrong direction. With a simple question as that we do not even need to create an equation. Fire doesn't have a definite chemical composition because anything that is flammable can cause fire. It ain't a process either, it is the effect of the process called burning. Dr. Junix, Mon, 11th Jul 2011

the atoms may glow as the electrons jump shells but radiance is radiance & it has no mass? CZARCAR, Mon, 11th Jul 2011

no.. fire has no mass.. same as electricity.. you cannot measure the it's mass.. Dr. Junix, Mon, 11th Jul 2011

See the whole discussion | Make a comment