Maybe the Smurfs were thinking three crab-apples high, rather than three genetically modified giant granny smith apples high.
Just a thought.
Off topic, but still on smurfs.
Where did baby Smurf come from? Who was the daddy? Was Smurfette the mommy? I just get this bad inage of all the male smurfs standing in line outside Smurfettes door on Smurf pay-day
Sorry about that last post. I got so into the Smurf reading that I forgot about the fire.
First of all, all you Smurf Chatters should start their own thread. We’re playing with FIRE here.
Okay Tris, I’ve got an open mind about this, and your experiment w/ the copper coil may, in fact, work. (And no, I did not try it). But even if it does, I’ve got some problems with your methodology.
Touching/enveloping the flame as you suggest and blaming the resulting “snuff” on a lack of heat seems dubious. I’d be a more inclined to believe you if you told me to also try the experiment with a preheated coil that would not extinguish the flame.
Candle flames seem like pretty fragile creatures, and my guess is that wrapping them with a mini-slinky screws up more than their body temerature (like their convection patterns – in which case you’d be messing up their oxygen supply, right?).
Further, if it’s a question of “heating the fuel to an ignition point,” why should chilling the flame itself matter? I assume the wick is where the action is… shouldn’t I poke IT with my chilly prod to make the flame go “snuff”?
What I originally had in mind was a set-up in which a flame is lit in a chamber; the chamber is chilled; the flame goes out.
And Tris, don’t suggest trying my freezer… how could I freeze fire when I can’t even keep ice cream hard in there? (Joke.)
No, you need a non-conducting coil of the same dimensions, as a control. It is not the temperature of the coil that cools the fire, but the rapid cooling provided by the highly conductive copper.
The wick is where the effect it, but the cause is the radiant energy from the flame. That energy is what raises the temperature of the wax and evaporates it as it is wicked up the . . . well, wick. When you cool the gases of the flame, they stop radiating and the temperature of the wax drops below its ignition temperature.
Tris
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- Assuming you blow flammable gas out of a straight tube, microscopic flames are ring-shaped. And Gargamel does kinda walk bent over.
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- I have just realized: “the Smurfs” is entirely leftist. We have minorities (blue skinned native people), women (one, anyway), and a disabled person (Gargamel) who is also an opressive white male. And his angry pet (the cat) to top it all off. This looks bad. This looks real bad. - MC
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I agree that a non-conductive coil is a good control, but a preheated copper one (perhaps without the long copper handle to suck away the heat) should fit that bill. But no matter, I’m much more interested in the second part of your post. You say:
“When you cool the gases of the flame, they stop radiating and the temperature of the wax drops below its ignition temperature.”
Seems to me what you’re really doing is starving it of FUEL by preventing the SOLID wax from melting into the LIQUID wax that is really what feeds the flame. Sort of like freezing a car’s gas tank solid and saying, “Look, cold makes the engine stop!” No, it just prevents fuel from getting to the combustion chambers.
We could test this using a liquid fuel (say oil, kerosene, or alcohol) lamp instead of a candle, wouldn’t you say?
Could you have a fire in absolute zero?
This would be true, if the snuffing process needed to wait until the already liquid wax on the wick solidified. But the actual experiment (if you do try it) will reveal that the flame goes out immediately. The coal at the end of the wick remains red (burning) for a moment or two until it too cools and goes out.
Yes, ** we ** could. But I already did, years ago. A kerosene lamp won’t work at about -55 degrees F. It doesn’t work very well at any temperature below about -15. If you check out cold weather gear for extreme climates you will find lamps where the fuel reservoir is above the light. You have to be very careful not to let them get to hot in warm areas, cause they catch fire rather spectacularly. Alcohol burns at a lower temperature than kerosene, and is very good for very low temperature use. It also does not thicken up as it cools, so it can be used in a simple stove even in low-pressure low temperature areas like mountaintops.
Tris
Fascinating thread.
And you smurf hijackers really suck. Go throw apples in a chat room or something.
But back on topic: This is totally non-scientific, but I just lit a lighter, then held it in the freezer. I didn’t notice any difference in height. My understanding was that heat was required for a fire to exist, so that below some temperature threshold a fire couldn’t be. But above that threshold, additional heat didn’t create additional fire. I’m not certain on that, though.
Perhaps on topic: I remember a fun trick from high school. You take a bunson burner with say a 4" high flame. You put a screen mesh over the flame, say 1" above the base of the flame. The mesh squashes the flame, so now it’s 1" tall. You take a second mesh and put it above the first and level with it, so it’s say 1/2" above the first (1 1/2" above the base of the flame). You can now light the flame above the top mesh, so there is flame below and above, but not in the middle. I don’t know how this relates to the topic, but I wonder what the temperatures would be in each of the three areas. Is the middle region noticibly cooler?
Yes, this is a fascinating thread, and I wish we could get more serious-minded posters to join in. The Smurf morons are ruining the property values in our neighborhood. I hope we’ve seen the last of them.
Now, back to my buddy Tris and his last post…
First of all, I ask that you please lose the patronizing tone. I’ve got an open mind about this, so we should walk hand-in-hand into the realm of scientific discovery as brothers, not adversaries. That said…
No, I did not perform your copper spring experiment (but see below), but as I posted earlier, I’ve got problems with it’s methodology even if it works as you say. The coil could be screwing with the oxygen supply, not chilling the flame.
I thought you made an excellent point with your camp stove argument, though. But as I pondered it more, I realized that we may be dealing with a fuel-starving issue again, not a temperature issue. You even allude to it yourself: the cold makes the fuel less viscous. I suspect that it’s not that it won’t burn; it just won’t flow. (Or spray, as the case may be).
In the spirit of brotherhood and scientific discovery I will try your coil experiment(s) tomorrow (actually, later today… damn it’s late) and report my findings.
Meanwhile I hope other posters who can help illuminate (pun) this issue will join in.
I don’t know how convincing this evidence is but I will forward it for your consideration.
It is a LOT harder to get a campfire going in the middle of winter than in summer. Summer usually all that is required is a small pile of kindling. Winter on the other hand, usually requires an application of kerosene and a large pile of kindling. This is based on my experiences camping with my buddy in the Sierra Nevadas, as far as I could tell there was no difference in the wood aside from it’s temperature and the tempature of the surrounding air.
In the winter, the wood’s probably wetter.
Consider it lost. It was inappropriate.
Well, we did this in high school chem lab, but we didn’t try the non-conducting coil. We did do it with a Bunsen burner, though, where the air is mixed in at the bottom of the tube, and the flame is at the top. It does snuff the flame. (You have to have a fairly heavy wire, with a Bunsen burner, though, cause those suckers put out a lot of heat.) That would seem to eliminate the “block the oxygen” aspect, since the mixture is the same before and after the wire is inserted.
OK, here, the Bunsen burner thing is on point again. The natural gas is still a gas, even when you snuff the flame. Viscosity is a problem, I agree, in the kerosene lamp, and in any liquid fuel delivery system. I think that is an unrelated issue, though on the kindling temperature requirement for burning.
Lacking proper laboratory facilities, I must try to locate some basic chemistry texts, and review combustion. I am pretty sure the explanation for why temperature is important would fit in a longish post, I just don’t recall it well enough to risk posting it on this particular board.
Again, please forgive the snotty side comment.
Tris
I don’t pretend to have any expertise on this subject, but from what I remember at school, for an oxidation to take place, an activation energy is required. In effect this means that at a certain temperature, a cup of petrol will spontaneously combust (don’t know what that teperature is but probably several 100 degrees centigrade). However, a spark, despite not having any heat, is at 1000s of degress C and can therefore trigger the reaction on a small scale even in the middle of antartica, and once started it generates more activation energy as the reaction is exothermic.
I don’t remember anything about an external source of heat being required after the initial reaction (where does this idea of fire needs heat come from? Science or fire safety advice?) I would suggest that yes you could have a small fire if you could regulate the oxygen supply, but I don’t know about the heat.
This also begs the question, what exactly is a fire anyway? Simple oxidation can take place without a flame. Is it something to do with reversible reactions? Are there any chemists out there with answer?
From http://www.m-w.com
"Main Entry: 1fire
Pronunciation: 'fIr
Function: noun
Usage: often attributive
Etymology: Middle English, from Old English fyr; akin to Old High German fiur fire, Greek pyr
Date: before 12th century
1 a (1) : the phenomenon of combustion manifested in light, flame, and heat (2) : one of the four elements of the alchemists b (1) : burning passion : ARDOR (2) : liveliness of imagination : INSPIRATION
2 a : fuel in a state of combustion (as on a hearth) b British : a small gas or electric space heater
3 a : a destructive burning (as of a building) b (1) : death or torture by fire (2) : severe trial or ordeal
4 : BRILLIANCY, LUMINOSITY <the fire of a gem>
5 a : the firing of weapons (as firearms, artillery, or missiles) b : intense verbal attack or criticism c : a rapidly delivered series (as of remarks)
- fire·less /-l&s/ adjective
- on fire 1 : being consumed by fire : AFLAME 2 : EAGER, BURNING
- under fire 1 : exposed to fire from an enemy’s weapons 2 : under attack "
I suppose it depends on whether you use definition 1a. or 2a.
It seems to me there are two issues.
The first is the size of the fuel supply. Given that any particular oxidation/reduction reaction has a rate of fuel consumption, your stick of wood (or whatever) can only be so small before there’s not enough to sustain what we would reasonably call a “fire” (the operative word being sustain - it would be gone in an instant).
But what about if we have a bunsen-burner-type setup, where the fuel supply is continuous, only we throttle it down? Theoretically we could throttle it down to a few molecules per second or some such thing, right? Then I suppose the other issue is, what is the minimum rate at which the fuel can be supplied (above the minimum requirements just to provide fuel at a high enough rate) and still sustain a fire?
What I mean is, an ongoing “fire” needs to be kept above a certain temperature (otherwise not enough heat energy to be self-sustaining). Below that temperature, even with a sufficient fuel supply, no fire. So the other issue is that temperature.
So, my question (at last) is, does the minimum rate required just to keep from running out of fuel generate enough excess heat to also keep the fire going, or not?
I suppose some of this may depend on the efficiency of the fuel…are there constants for various fuel types that can be used to calculate this? E.G., for a given fuel mixture we could know the minimum rate of fuel consumption, plus the minimum temp required to sustain the reaction (it seems like for pure oxidation/reducion theses numbers ought to be constant, but we need to take into account fuel impurities and what have you…)
Anyway, if we knew the numbers we could calculate the theoretical “smallest” fire for a given fuel…
First of all, Tris, thank you for your graciousness. Don’t give it another thought.
I have not tried the wire coil test yet, so I have nothing to report on that front. Soon, I promise.
Suspicious Mind brings up a point that probably should have been clarified earlier: namely that the issue here isn’t whether heat (+ fuel, + O2) is necessary to START a fire – little arguement there – but whether it’s necessary to SUSTAIN one (or, as I asked way back in the beginning, “Can you freeze a fire out?”). Which leads me to a theory that has nothing to do with the science of this question…
I suspect – if one assumes the “fire needs heat” theory is, in fact, a myth – that the reason it is so widely believed is because, over the years, the distinction between what STARTS a fire, and what SUSTAINS a fire has been lost.
heat+fuel+O2=fire so why is it that you can burn straight O2? it seems to me that burning oxygen alone removes the fuel leg of the triangle. (or maybe the o2 just serves as fuel also?)
All right, you guys took what I said about what fire NEEDS and changed it into what is required to start a fire.
What a fire needs to START are three things: Ignition source, fuel, and oxygen.
Ignition source can be any number of things, for example, electricity, a match, or enough heat to induce combustion in that particular element ot compound. In essence these things do produce energy (heat), but the amount of energy is so much that it can induce a chain reaction, read fire.
What a fire needs to sustain itself are three things: fuel, oxygen, and HEAT.
Lets think about how we need heat to sustain a fire.
So we have a stick with one end on fire. That fire is burning slowly, lets say 1 foot of the stick per minute. Now if we cut the stick right next to the fire, then it will run out of fuel and die. If we take anouther stick and put it next to the end that is on fire, then we will have a bigger flame, cosuming more of the stick. This is a simulation of adding or taking away fuel.
Again, we have that same stick with one end on fire. Now we take an oxygen tank and open the valve next to the fire. With this influx of more oxygen the fire grows. It then starts to eat up more of the stick because it is a bigger fire with more intense heat. Now we take our Oxygen-Suck-O-Matic and suck all the oxygen from the area around the stick. Because there is less oxygen the fire dies down until it finally dies altogether. This simulates giving or taking away oxygen.
Now to explain the relationship of heat to a fire’s survival we need to examine what a fire does. So we look at our stick that has one end on fire. What is happening is that the flame is transfering some of it’s energy to the un-burned portion of the stick. This increases the temperature of the un-burned portion of the stick until it gets so hot it too catches flame. This continues until there is no more stick. Now we know that if we decrease the temperature around an object then that object’s temperature will also decrease. So if we decrease the temperature around the stick, the stick’s internal temperature will lower itself. Well now the flame needs to exert that much more energy to ignite the un-burned portions of the stick. If we keep decreasing the temperature of the stick we will eventually lower the temperature so much that the flame can not produce enough energy to ignite the un-burned portions of the stick, thus it will die. Simply putting a candle in the freezer will not show this, the temperature change of maybe 40-50 degrees F is not enough. You would need to be in the deep of winter in Siberia for this to make much of a difference, I suspect.
Hope that was clear enough.
And to eggo:
You are correct, in the case of burning straight oxygen, the oxygen acts as it’s own fuel. Probably the most efficient way of having a flame since two of the three requirements of fire are the same element. Isn’t that what they use for the boosters of the space shuttle? I think I may be wrong, I am not too sure.
-N