Sunday, June 03, 2012

Something Borrowed, Something Blue

UPDATE:  The answer is here

Update Notice:  The spam filter is going nuts, and the video is from Vimeo and is not loading sometimes.  The video can always be found at the Flame Challenge site below.   Since Google owns YouTube and Blogger, let your inner bunny paranoia run free.
The Flame Challenge arose from an 11 year old Alan Alda's wonderment
I’d like to try a playful experiment. Would you be willing to have a go at writing your own explanation of what a flame is—one that an 11-year-old would find intelligible, maybe even fun? The Center for Communicating Science is looking for new ways to light up people’s minds with science, and you might point the way. We’ll try out the entries on real 11-year-olds and see which work best. . . .
So here I am—I’m 11 years old and looking up at you with the wide eyes of curiosity. What is a flame? What’s going on in there? What will you tell me?
and the winner is Ben Ames, an American graduate student work on his doctorate at the University of Innsbruck in Austria.  The video is great.  Show it to your 11 year old.  They will love it and so will you.
The problem is that there is a huge mistake. Bunnies need to figure it out and report back. Eli will post the answer tomorrow. The Rabett offers you a hint in the post title.  There are lessons to be learned.


Anonymous said...

Let me be the first to be wrong.

He's got pyrolysis wrong.

Mark said...

This probably isn't what Eli had in mind, but the video depicts the fuel as methane, when it's actually long-chain hydrocarbons.

As to what Eli more likely has in mind is it fluorescence, not chemiluminescence?

Martin Vermeer said...

Hmm, the dog that didn't bark... nitrogen? What causes there to be too little oxygen at the moment when it's needed

Anonymous said...

Well, according to the video credits the guy's name is Ben Ames, not Amis. But that's not what mr Rabett was looking for, I suppose...

Sou said...

Very topical. Last night I carried out a flame experiment in the Kitchen. The flame burnt red, orange and yellow and was hot.

The experiment was not intentional and now I need a new rangehood and lots of sugar soap :(

There was no flame to start with, just heat. Heat applied to olive oil = pyrolysis I guess.

Orange, red and yellow flames came from the burning oil spontaneously igniting as it got hot enough and vapourised, and it left a black soot over everything, and smelt awful. The oil left behind was thick with lots of black goo.

Could have been much worse.

Imback said...

I don't know what Eli was thinking of, but I wonder about the claim at 3:20 that the blue light is not hot. The video goes on to explain heat from conduction but neglects to mention heat from radiation. The blue light from a birthday candle may not have much radiative heat, but blue light from some flames certainly can.

EliRabett said...

Corrected. Thanks

Rattus Norvegicus said...

The fuel does not lose mass.

willard said...

I don't believe atoms are green Legos.

Atoms let go of the legos long time ago.

Anonymous said...

Jerry Garcia knew the answer:

Let us put red and blue flames together
See which one is hotter
Some say red, but I say blue
Blue trumps red like many trumps few

It ain't me
It's the scientists that say
Red flames are leading the graduate students astray
But I say, it's the blue flame today
Hotter than the red in every way

That's right
The blue-flame is hotter
That's right
The blue-flame is hotter
That's right
The blue-flame is hotter
The blue-flame is hotter that's right that's right


Following is from "Candles" (by Chris Woodford

"The hottest parts of a candle flame are actually the blue, almost invisible area near the base, where oxygen is drawn in, and the blue/white part around the edge, where the flame meets the oxygen-rich air all around it. The flame gets progressively cooler as you move in from the outside edge toward the wick. Cooler areas are darker and colored orange, red, or brown. Most of the flame's heat is delivered toward the tip, where a large volume of gas is always burning and convection is sweeping hot gases constantly upwards. If you want to heat something with a candle, hold it near the tip."

Anonymous said...

Huh, I had thought of chemiluminescence as firefly type light - chemical reactions producing light, where candle flames were just straight up heat, and the different colors are different blackbody temperatures. suggests that in fact, there is chemiluminescence going on, but in any case, the description in the video was wrong: it isn't that there the fighting excites atoms which put out light, but rather that in the process of breaking things apart, there are generated some excited atoms, which put out light. Subtly different.



bill said...

I once asked this very question in a High School physics class - the teacher didn't know, and came back with 'fluorescing super-heated gas' a couple of days later. It would appear he was close, but gains no long furled tobacco product.

I subsequently went to Art School - disappointed by an unconvincing flame - and this is my eternal excuse fer any iggerance on my part.

However; what's incandescence? Things just 'glowing because they're hot' isn't cutting it for me.

Nice home-grown poodle-rock meets the Arcade Fire anthem at the end there; I sure hope he doesn't have to change something in it.

EliRabett said...

Incandescence is when something glows when it is heated, like sticking a piece of iron into a fire. Stefan Boltzmann and all that.

Phil. said...

The best description of a candle flame was Michael Faraday's, 'The Chemical History of a Candle', based on his series of lectures to children at The Royal Institution.
The Christmas Lectures for children still continue having been started by Davy in 1826.

Anonymous said...

anon@3/6/12 4:04 PM,
Not bad but:
-It was a Bobby song (not Jerry’s).
-Bobby got it from Harry Belafonte.
Keep trying ;-)

arch stanton

EliRabett said...

Yes, but Faraday needs an update because of all that we have learned since then

Anonymous said...

Hey, Ben Ames here!

Eli, you are awesome for clarifying this point. My original animation was over 10 minutes long. Instead of the reacting atoms in the ring, I originally had the hydrocarbon and oxygen molecules playing a game of leapfrog, showing the transition reactions, including various free radicals. I attempted to explain that those transition products had too much energy and got rid of it by spitting out blue light---a more detailed and accurate explanation of chemiluminescence. To cut on time and simply even more (a painful thing for me to do) I just covered that whole process in a fight cloud and explained it as atoms shining light as they rearrange.

The most misleading element is when I say, "when certain atoms get hit hard enough, they spit out blue light." I was careful not to say what was hitting them hard, like photons, in the case of photoluminescence. The general idea that I wanted to get across was that when things get "hit hard" with energy, molecules can break apart and sometimes emit light. The animation generally associated with photon absorption and stimulated emission only adds to the confusion. Ah well, my explanation exists more refined in some distant parallel universe.

Thanks for the analysis. It is always good to get the community talking about science!

EliRabett said...

Ben, more to follow. For example one of the important things about flames is that the more unsaturated the fuel (that means in chem speak the lower the ration of H to C) the smokier and hotter the flame. If you don;t pour in extra oxygen you produce copious soot. We can trace soot production from C2 species to C3 but not much beyond that and the mechanism for soot production has a lot of holes in it.

However, once you have carbon particles, the bonds are so strong that it is hard to react them. By then it is too late.

Next Fall, Eli will use your video and some modern spectroscopic and electronic instruments in a PChem Lab to study flames:)