frozen fire

[bored_teen]

i've always thought it would be impossible to freeze fire. but the question stuck in my mind this morning, and i've been thinking about it all day. could you do it? fire needs heat, fuel, and oxygen to continue to burn. let's assume you have a fuel source that is small, but burns for a very long time. the fire will keep burning as long as it has air because it produces its own heat. could you freeze a fire in oxygen?

[Pantaz]

Fire is a chemical reaction, not a substance. There is nothing to freeze.

[bored_teen]

i understand that fire is a reaction. in essence, could you freeze the fuel source, as well as the oxygen surrounding it, causing the reaction to continue in the frozen state?

[YT2095]

a simple definition of fire is Gases so hot that they glow.

 

the operative word here being Hot.

and so by virtue of that, if you rob it of the Heat, it will cease to be and just become a gas.

[bored_teen]

a simple definition of fire is Gases so hot that they glow.

 

the operative word here being Hot.

and so by virtue of that, if you rob it of the Heat, it will cease to be and just become a gas.

 

i'm under the impression that, while a lit fire needs heat, that heat comes from the chemical reaction (basially it produces the heat it needs). if you instantaneously froze the fuel source, the oxygen, and the chemical reaction (fire), would the fire keep producing its own heat, or would the temperature change snuff it out?

[Gilded]

There isn't that much of a chemical reaction going on in the flame itself, it's just gas molecules that are hot enough to emit photons in the visible spectrum. The flame doesn't really produce heat to begin with, it's the chemical reaction in the fuel that does. If it was possible to somehow flash freeze a flame I'd imagine it would turn into a powder of various crystallized chemicals. If you flash freeze the fuel the flame will quickly disappear (disappearing meaning that it disperses, cools and stops glowing), for the simple reason that the chemical reaction that produces the flame (the hot gas mixture) has stopped.

[bored_teen]

There isn't that much of a chemical reaction going on in the flame itself, it's just gas molecules that are hot enough to emit photons in the visible spectrum. The flame doesn't really produce heat to begin with, it's the chemical reaction in the fuel that does. If it was possible to somehow flash freeze a flame I'd imagine it would turn into a powder of various crystallized chemicals. If you flash freeze the fuel the flame will quickly disappear (disappearing meaning that it disperses, cools and stops glowing), for the simple reason that the chemical reaction that produces the flame (the hot gas mixture) has stopped.

 

ok. the part that i don't understand is where the heat comes from. you need three things to produce the reaction causing fire, those being fuel, oxygen, and heat. let's take the case of rubbing 2 sticks together and producing a flame. the stick is the fuel, the oxygen comes from the air, and the heat needed comes from the friction from rubbing the sticks together. to continue burning, the fire needs heat, oxygen and fuel. the fuel and oxygen are coming from the same place they were to start with, but, seeing as you've started a fire, you stop rubbing the sticks together, removing the friction that provided the heat to begin the reaction causing the flame. where does the heat now come from? or, am i completely wrong in thinking the fire needs heat to continue?

[Edtharan]

Fire is a gas that is so hot (due to chemical reactions) that it glows. This is the same as the filament in an incandescent light globe. If you cool it down, it is no longer hot enough to glow. So, if you were to "freeze fire", you would have to cool it down and it would then stop being "Fire".

 

So no. It is therefore impossible to freeze fire as to do so would stop it being fire.

[bored_teen]

Fire is a gas that is so hot (due to chemical reactions) that it glows. This is the same as the filament in an incandescent light globe. If you cool it down, it is no longer hot enough to glow. So, if you were to "freeze fire", you would have to cool it down and it would then stop being "Fire".

 

So no. It is therefore impossible to freeze fire as to do so would stop it being fire.

 

now i'm kind of hung up. i can start a fire just as easily at the north pole as i could at the equator. is it just that the arctic air isn't cold enough to cool the fire enough to put it out?

[Phi for All]

i can start a fire just as easily at the north pole as i could at the equator.

This is a false assumption. It's actually easier to start a fire in a hotter climate. The ambient temperature aids the chemical reaction.

 

Forest fires are more prevalent and burn longer in hotter climates.

[bored_teen]

This is a false assumption. It's actually easier to start a fire in a hotter climate. The ambient temperature aids the chemical reaction.

 

Forest fires are more prevalent and burn longer in hotter climates.

 

i'm taking this to mean that i was right about the arctic not being cool enough to put out the fire. so, what's the temperature where a fire stops burning due to a minute temperature drop?

[Gilded]

You're looking at this the wrong way. A flame isn't something that "needs" certain things such as heat, it's just a product of a chemical reaction, and is hot/energetic by definition, as mentioned by Edtharan. In the rubbing sticks scenario the chemical reaction in the fuel keeps going once you've added a required amount of energy to system (with the sticks), and this reaction is what produces the hot gases that are seen as a flame.

[bored_teen]

You're looking at this the wrong way. A flame isn't something that "needs" certain things such as heat, it's just a product of a chemical reaction, and is hot/energetic by definition, as mentioned by Edtharan. In the rubbing sticks scenario the chemical reaction in the fuel keeps going once you've added a required amount of energy to system (with the sticks), and this reaction is what produces the hot gases that are seen as a flame.

 

so if i have fuel, and i've put in the required amount of energy, why can't i freeze fire in pure oxygen? unless, as the climate gets colder, more energy is needed to start a flame, and thus cooling the fuel which is on fire increases the amount of energy i need to start a fire, so when the amount of energy needed exceeds the amount i've put in it goes out? if that is true, then could you flash freeze fire in oxygen if you had

1. a stick that

a) retained the dimensions of a normal stick, but

b) provided infinite fuel

2. an infinite source of constant energy to provide for the fire?

[Cap'n Refsmmat]

As you "steal" energy from the fire, you'll eventually remove enough to make the combustion reaction unable to continue (assuming you're removing energy faster than the fire creates it). So if I had a match burning and dumped it in a vat of liquid nitrogen, it would "freeze", although there would be no "fire" per se -- the flames go away when the heat goes away.

[bored_teen]

because i'm talking about freezing fire in pure oxygen, i need to understand some other things. first of all, liquid oxygen is highly flammable. does it act as the fuel source? if so, if you froze it and it was still on fire somehow, wouldn't the fire just melt the oxygen?

[Cap'n Refsmmat]

Oxygen isn't flammable by itself. It still needs fuel. It's just that combustion reactions require fuel -- take, for example, the combustion of natural gas (which is mostly methane, CH₄):

 

[ce]CH4 + 2O2 -> CO2 + 2H2O[/ce]

 

The [ce]O2[/ce] won't burn. It's only facilitating the combustion of the methane.

[bored_teen]

ok, so oxygen by itself can't be fuel.

 

anyway, i still don't seem to be getting all of this. what i've understood that has been said is that flash frozen fire will be extinguished because it gets cold. fire is basically superheated gas, so cooling it would put it out. but, because the reaction has already started, wouldn't the reaction on the fuel heat more gas? or, would it not be able to heat more gas, because the environment has a greater capacity to cool the gas than the current reaction has to heat the gas? and, since the oxygen is frozen, would the fire even be able to burn the frozen oxygen? if i'm right about the environment having a greater cooling capacity, would originally having put enough energy into the reaction before it was frozen to give the reaction a greater heating capacity than the flash-frozen environment has cooling capacity enable the reaction to continue after being frozen, or would it instead just not freeze?

[Gilded]

There's not much going on in the flame itself, chemically that is. Sure, there's small amount of volatiles but if you add pure oxygen to a "separated" flame anything oxidizable would be gone in an instant. And if by frozen oxygen you mean oxygen that's been frozen solid there's no way a normal burning reaction could take place at those temperatures. I'm not exactly sure what sort of exact scenario you have in mind.

[YT2095]

fire needs heat, fuel, and oxygen to continue to burn.

 

you said it yourself.

 

it`s the basic Fire Triangle as taught in junior school, it needs all 3 of the elements to maintain itself, remove ANY one of these 3 and no fire!

[bored_teen]

i think i finally get it now. basically, there's a certain amount of energy in the reaction. once the environment can cool more than the reaction can heat, no more fire.

[YT2095]

Bingo!

[Edtharan]

i think i finally get it now. basically, there's a certain amount of energy in the reaction. once the environment can cool more than the reaction can heat, no more fire.

Yes. In a fire there is a chemical reaction (and exothermic reaction - that is it produces heat). However, if you can take the heat away faster than the chemical reaction can generate it, then the fire will go out.