stuyguy said:
OK, so what we really neeed here is a relatively cold flame that uses a liquid as a fuel. The liqiud needs to remain liquid at relatively cold temperatures, so as not to alter the fuel source. Then, we need a bottle of oxygen for a “food” source, and a blast freezer. Does anyone here access to those facilies? Maybe someone in the restaurant or industrial professions?
The wire loop experiment with the bunsen burner would also be acceptable, I suppose, if you also tried it with a nonconductive coil of some sort (ceramic?) as a control. Unfortunately, I don’t have access to the relevant equipment.
KC… may I call you KC? you can call me stuy… I think you raise some valid points, but others I question.
I concede that you are probably right that the gaseous make-up of breath is not sufficiently O2-lean to smother a flame. In fact, in the other thread I talk about how I’d lightly blow on candles, and make their flames “struggle” to stay attached to the wick, so I’ll admit that’s true.
But is blowing out a match/candle really a heat-starving action? I’m not so sure. It is probably more akin to “disconnecting” the flame from its fuel supply (i.e. starving it of fuel).
As for convection currents, no I do not consider them heat, and (forgive my shameless pandering…) neither does Cecil. In his column about flames in zero gravity, he describes convection as a sort of cleansing system by which smoke and waste gases are carried up and away from the flame, and cool (yes, he wrote “cool”) oxygen-rich air rushes in. And yes, if you screw with that process you’re not playing fair in the experiment (at least in my book).
Thus, combining the concepts in the above two paragraphs, “fanning the flames” is like a turbo-charged convection system that is not so aggressive as to disconnect the flame from it’s fuel.
Let’s talk about bunsen burners. I searched my memory back to my Qual-Anal Chem classes. If I’m not mistaken, it is not hard (though certainly not desirable) to get a flame to burn like gang-busters INSIDE a Bunsen burner tube. I think a weak gas jet + a wide open air stream will do it… I’m not 100% sure if I got the combination right, but I know it can be done… and you don’t have to heat the tube or anything like that either.
And Necros, thanks for your post. At least it seems like you have some appreciation of why I consider all the prior demonstrations flawed (not necessarily invalid, mind you, just flawed). Boy I was feeling lonely.
Perform the Bunsen burner/wire experiment twice. Once with a cold wire (already done) and once with a hot wire (perhaps heated with a second Bunsen burner). You’ll want to verify that the wire isn’t so hot that it actually starts a fire. Ideally, it should be almost that hot.
Zen: I suggested exactly this test in the other thread. Alas, I do not have a BB, so I could not try it.
I sort of tried it using a candle (I describe it two posts ago); I eased the coil down the flame to get it “preheated.” But fast or slow, it did not matter – the flame stayed lit.
(In fairness to Tris, I will try it w/ a copper [better conductor] wire as he described, not just the steel one I used. Alas, I have no such wire either, so it will have to wait til later.)
UPDATE ON ANOTHER TEST: Last night I tried the experiment I proposed in the “How small can a fire be?” thread. (Namely, ignite a small pool of liquid fuel in a shallow metal vessel, at dip underside of vessel in ice water. Note result.) I used a stainless steel teaspoon half-filled w/ rubbing alcohol.
Result: the fire seemed entirely uneffected by the contact with the cold water and kept burning.
Eventually it went out (say 30 to 60 secs. after contact), but I suspect it was because all the alcohol was consumed; there was still liquid in the spoon, but my rubbing alcohol is only 70% alcohol (the rest H2O) so it probably was not combustible. (It was VERY late. I was VERY tired. So I did not think to check. So sue me.)
One more example.
If you take a burning piece out of the “coals” in a fireplace and set it on the hearth it will go out. Its brothers in the fireplace contiue to burn. The only relevant difference is the temperature. You can keep the coal burning for longer, even outside of the fire, by insulating it. Carbon needs a high temperature to sustain combustion.
As for the CO2 in breath, you can blow out a match with a fan just as easily.
Hey Frol… I already ate crow for my glib and bogus CO2-breath remark. Enough with the fan already.
As for your coal example, I will give it some serious thought. I like the twist that the coal seems to need higher-than-room-temp to burn, so that it considers normal temps as chilly. Hmmm…
(One quick clarification please: When you say the coals in your fireplace “burn,” do you mean “smolder”-burn (like a BBQ coal) or “flame”-burn (like a match)?)
well, this is what i have.
i lit the candle and walked into the freezer. the candle seemed not to mind. now i was in the freezer for only three min. and the candle stayed lit the whole time. this tends to suport the “you can’t chill a flame out” theory. if anyone wants me to conduct a more seintific expierment with the blast freezer here at work to try to support or disprove the chill theory, i’m open to ideas and sugestions
Then why doesn’t the air burn in a fire? Why didn’t the first fire in the history of the Earth incinerate the atmosphere?
This is the most exasperating thread I have read. Here are a couple of points.
The heat released in “flame” is enormous compared to any difference in room temperature. A burning log will burn the same in -30 F weather or 100 F weather.
This just not mean that you can’t “chill” a fire out.
Fire is oxidation of a fuel, i.e. fuel + oxygen —> FuelO + heat (flames).
A flame is ionized air that results from the heat released by an oxidizing fuel.
There is a Activation energy initially required by a fuel to begin burning. Once it burns, the exothermic reaction of the reaction is easily enough to supply the activation energy for more fuel to burn.
Alcohol, paraffin, wood all burn and release relatively enormous amounts of heats.
The bunsen burner is probably the best instrument to test your hypothesis out because it uses methane which doesn’t release as much heat as alcolol, paraffin, or wood when it burns, though ideally we would like to find something that burns a little less hot, maybe methanol fumes?
methane is a good tool to test the hypothesis out because it is a gas/air mixture. You can “smother” this type of flame from oxygen with a liquid.
All of this being said, there is an incredibly simple way to find out if you can chill a fire out. Typically in a college lab you have a steam and air feed. spray them both at the bunsen burner. If you have enough steam, the fire will go out because the steam will absorb all the heat being released by the burn, and new methane coming out won’t ignite. You are also blowing air into the flame, so don’t give me the “oxygen smothering” argument.
There are some commercial applications where they use steam to regulate the temperature of a flame. More steam, more heat absorbed, lower temperature flame. Too much steam, too much heat absorbed, no flame? get it?
Quoth Milossarian:
Oxygen itself is not a fuel. A fuel is something that combines with oxygen. Although you can combine three O[sub]2[/sub] molecules to form two O[sub]3[/sub] molecules (ozone), this reaction is endothermic, which means that it requires more energy than it releases. The other major component of air, nitrogen, can also be burned, but again, it’s endothermic.
The exception to this is the combination of oxygen and fluorine: For various technical chemistry reasons, the oxygen is considered to be burning in the fluorine, not the other way around. I believe that fluorine is the only substance for which this will work. Regardless, there’s little, if any, fluorine in the atmosphere, so this isn’t an issue here.
FWIW, you can extinguish a match with a sufficient quantity of gasoline. I don’t recommend trying it, tho.