Naked Science Forum
General Science => General Science => Topic started by: chris on 25/12/2006 20:15:30
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The other day, as I was watching someone enjoying an increased risk of heart disease and lung cancer in the form of a cigarette, I began to wonder why the smoke, which they were good enough to share with me and the other people standing nearby, is a blue colour?
Is it related to the smoke particle size?
Chris
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Maybe because of it being a type of vegetation, perhaps it's the cellulose in the plant life! Grass fires and other plant fires produce a type of blue smoke also! I am by no means an expert, but that would be my humble guess!!
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I found this on the net... At " A moment in Science Library" (Trustees of Indiana University)
"When someone is smoking a cigarette, aside from the hacking and coughing, have you ever noticed that the smoke curling off the tip of the cigarette is blue, but when the smoke is exhaled it's white? We know that some nasty things are happening to the lungs, but why does the smoke change color?
The smoke changes color because the size of the smoke particles changes. The smoke particles rising from the cigarette tip are very small--smaller than the wavelengths of visible light. Because the particles are so tiny, when most light waves strike one of them they are not reflected back like a bouncing ball, but only slightly deflected from their paths. This is called "scattering."
The various colors of light have different wave lengths, and the ones toward the blue end of the color spectrum are the shortest. So the short, blue waves are scattered about more by the tiny smoke particles because they are closer to the same size. Since mostly blue waves are scattered about the area, we see the smoke as blue. Most of the other, longer wavelengths go almost straight past the particles and we don't see most of them.
Smoke particles that are sucked into the lungs are a bit bigger because they are not burned down completely. Many of them will remain in the lungs, hidden from the world until the biopsy. Many are exhaled, though, and when they come out they have changed again. While in the lungs, and on the way out, they pick up moisture so they become bigger still. The particles are now big enough to reflect all wavelengths of light equally. When all the wavelengths are reflected back they make white light, and so the smoke looks white."
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It's blue for the same reason the sky is blue.
It's down to the scattering of light by the particles in the atmosphere.
In this case the atmosphere is smoke.
The particles scatter more blue light than red light so you see it as blue.
*inaccuracies and mistakes are to be blamed on half a litre of JD&coke*
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This reminds me that the exhaust of a well running two-stroke engine is blue, too. But in some cases it is not : a cold engine will emit white smoke (water vapour condensing ?), excess oil in your mixture may give black smoke (as from a diesel-engine when your open the throttle). Anyone around with an explanation ?
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Diesel is fuel oil, unlike lubricating oil, its more like kerosene or jet fuel! Black smoke is too much fuel in the fuel air mixture. It's is not burning cleanly!
Blue smoke is, oil getting into the fuel air mixture! There should be no oil in this mixture! Diesels accelerate by injecting a large amount of fuel into the combustion chamber, therefore , especially in older designs,it does not burn efficiently upon that excelleration!
On the more modern diesel designs the black smoke is much reduced..and as a matter of fact California will mandate new very stringent emissions standards for commercial deisel applications, such as trucks.These mandates should take place in the next year or so!
I am no expert, but know a little about engines and Have two sons who are very knowledgeable under the hood so to speak, and my husband drives a semi and knows quite alot about diesel engines .. My mechanical boys are also a source of my knowledge... White smoke as you say is really vapor etc. From water condesation and build up in the cold pipes and as your engine warms it evaporites the condensation build up and the white smoke (steam) goes away!
I know some because I had to read a diesel Mechanics book to my son for his tests to enter a program in colorado technical Intitute where he will be studing disel mechanics! He has been working on them for soome time and has a lot of knowledge.. The book I tutored him in was about 4 inches thick Large hardback book that looked like a huge family bible about 16 or 18 inches tall and about 12 inches wide!! It was a big puppy! I learned alot..
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Thanks, Karen, but I was thinking more of two-stroke petrol engines. Two-stroke diesel engines do exist, river barges over here are usually equipped with them, and they do emit all kinds of smoke. Did your book say anything about two-stroke diesel engines ? They seem to be running much cleaner than the diesel engines in trucks !
Due to emission laws, two stroke petrol engines will probably disappear in the near future. But I have seen them emitting blue, white and black smoke - not at the same time of course. I remember that in the case of the black smoke, the mechanic first tried to solve the problem by changing spark plugs.
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Thanks, Karen, but I was thinking more of two-stroke petrol engines. Two-stroke diesel engines do exist, river barges over here are usually equipped with them, and they do emit all kinds of smoke. Did your book say anything about two-stroke diesel engines ? They seem to be running much cleaner than the diesel engines in trucks !
Due to emission laws, two stroke petrol engines will probably disappear in the near future. But I have seen them emitting blue, white and black smoke - not at the same time of course. I remember that in the case of the black smoke, the mechanic first tried to solve the problem by changing spark plugs.
Blue smoke = tiny particles wich size is similar to air molecule's size.
White smoke = tiny water droplets (they form when an engine is cold, otherwise they become water vapour = transparent).
Black smoke = tiny particles of carbon from not complete combustion (it can depend on bad air-fuel mixing/proportions, bad sparkling ecc.).
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Hello Karen!
My compliments to your answers and to your knowledge about internal combustion engines!
Bye!
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THanks Alberto, I know some, trying to coach a child into trade school, Me had to read to him and quiz him. I wish I knew more, but I do have a limited knowledge of many things as I like to tinker me self!! I also want to be able to sort of trouble shoot my car if I am stranded somewhere!!
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Okay, so why is the shadow of cigarette smoke dirt brown and not black like the smoke from a fire?
put that in your pipe and smoke it.
[:)]
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Because the smoke scatters the blue light and allows the redder end of the spectrum to pass through it, so the shadow lacks blue and has a predominance of red so it look sort of brownish.
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Because the smoke scatters the blue light and allows the redder end of the spectrum to pass through it, so the shadow lacks blue and has a predominance of red so it look sort of brownish.
Good answer, Heliotrope.
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ahh... very nice... well ya learn something new
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Me too...I am an exsmoker..kicked that nasty habit years ago...
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Because the smoke scatters the blue light and allows the redder end of the spectrum to pass through it, so the shadow lacks blue and has a predominance of red so it look sort of brownish.
Thanks heliotrope! Hows your New Year coming along?