Do solids burn
- Thread starter Asguard
- Start date
Why don't you get some steel wool and put a match to it and watch what happens?
When an object burns, it is a chemical reaction of it changing from one state to another. It is like when you burn paper, the burning oxygen is changing the state of matter that the paper is in.
Here are some no-nos. Don't set off a spark in a coal mine with solid coal dust around. Don't set off a spark in a sugar refinery with solid sugar dust around. Don't set off a spark in a grain silo with solid wheat dust around.
Fraggle Rocker
Staff member
Well... the chemical reaction is two molecules recombining and releasing the energy in the bonds between their atoms. The resulting molecules have a lower vaporization temperature than the original molecules, and coupled with the fact that the energy released by the reaction raises the local temperature, the product of the reaction forms as a gas instead of a solid. Changing from solid or liquid state to gaseous state can be accomplished by raising the temperature of the material without recombining its molecules and breaking its chemical bonds. This is a physical process, not a chemical reaction.
This doesn't answer the question as clarified in the O.P. Does the dust turn to vapor before it burns? I'm positive it does not because of the example of steel wool already cited. Iron has a melting point of 2800 degrees (1500C) and a boiling point of 5200F (2900C). I don't know how low the air pressure would have to be to get iron to sublime (change directly from solid to gas), or if iron will even do that, but I'm sure the temperature would have to be pretty close to that.
There's no way any firestarting technology you have lying around the refinery will generate a temperature in that range.
Therefore I think it's safe to say that iron burns as a solid.
Sometimes the exothermic union of two molecules, neither one part of a solid, can result in a solid compound which has a lower vapor pressure. I am not a chemist, but think that is the case when Mercury is oxidized by Oxygen.
This reversible reaction happens to be the chemical process by which the law of definite proportions was first established as I recall. (By Lauvasia - terribly spelled, phonetically.) I am almost sure the solid red mercury oxide has a much lower vapor pressure / higher vaporization temperature than either of the elements from which it is formed. He used concentrated sunlight to endothermically decompose the solid red oxide inside a glass vacuum chamber - always getting Hg and O2 in the same ratio.
I am sure that iron will not sublime. - It is one of the preferred materials, nearly universally used for making large high vacuum chambers. At APL we had some large enough to hold major satellites for thermal-vacuum testing and all were made of iron.*
PS I thank you in advance for correcting my spelling of his name. I am 99+% sure you can without consulting any reference.
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*Sadly, two men working inside one on an APL satellite died. They had hand cranked up the very heavy iron "bell jar" from its iron base just enough to crawl under and enter. Unfortunately, the dry nitrogen gas supply value was still open and slowly caused the oxygen content of the atmosphere inside the bell jar to decrease. They lost consciousness and peacefully died. From this expericence I learned that humans do not, as most all believe, breathe to get oxygen. We feel the urge to breathe to get rid of CO2.** That they were able to do, so they breathed the steadily lower oxygen content "air" without any respirtory distress and died. (Their car-pool co-workers, wanting to go home, searched for and found them about 5:40pm.)
**If you think about it -this fact is obvious. When "holding your breath" as long as you can, the CO2 content of the gas in your lungs increases several fold - a change easily sensed biologically - but the oxygen content is barely decreased - hard for the body to sense that small percentage change.
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Has this got to the "is fire plasma?" stage of discussion... oh, no it did not, never mind.
Even if the steel wool burning does not persuade you otherwise, because you note the oxygen is a gas, the example of TNT should work. The oxygen is part of the solid matrix of the compound; it will burn very rapidly - explode - under water and in other non-gaseous media.
To beat this "dead horse" some more:
Hydrogen peroxide also. It too contains the oxygen, but is only a liquid not a solid. The Germans ran some U-boats on it. I think they operate under water.
spidergoat
Valued Senior Member
It depends on the surface area exposed to atmospheric or other oxygen. That is why solids in the form of powders, or wool, or fibers, burn so readily.
But isn't when an object lit on fire, the flame buring the paper is a chemical reaction? It does break the bonds within the paper. For example, when you burn the paper, you will notice that there are carbon ashes left over while the other elements have broken away from the molecular bond. Many of the other materials in the paper that I did not name would also have changed into a different state, seperated from the carbon.
actually as far as i know you have it BACKWARDS
Flame is just the light emited as a by product of the chemical reaction as is the heat releaced. The heat however does serve another purpose and that is as a catilist to cause OTHER chemical reactions in ajacent materal
Anyway so what i gather the gist of the responces here is the answer is MAYBE
Flame is just the light emited as a by product of the chemical reaction as is the heat releaced. The heat however does serve another purpose and that is as a catilist to cause OTHER chemical reactions in ajacent materal
Anyway so what i gather the gist of the responces here is the answer is MAYBE
That is correct. The light from most flames is a continuum of wavelengths, emitted by relatively large aggregates of atoms, such as microscopic pieces of wax when a candle burns. Some "flames" can be quite hot, yet hard to see - not much light emitted as they are "clean" for example an alcohol flame.
It is possible to have flame not making essentially black body continuum radiations from the hot microscopic particles in it. For example ordinary salt (NaCl) added to a flame will decompose, and then you will see the "sodium D" bright yellow line radiation.
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We had a poster, "Sandy" whose atvar was the same (or very similar) to USS Exeter's and the slogan under both claimed to be "hot/sexy/rich" etc. "Sandy" posted a lot of silly things* too, IMHO, but many have proven to be false so she is no longer active here now. Is it possible to know if USS Exeter is just Sandy with a new name?
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*Sandy was not too realistic but always very optimistic. More than year ago told how she was buying up property - expecting to get even richer on it, etc. At least she should have waited until now (and much longer IMHO as has another 15 % to fall at least.).
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spidergoat
Valued Senior Member
Not a chance, too smart.
No no, DO set a spark off. Preferably when there is nobody else around.
What you can do quite easily is blow some flour out a tube over a candle flame. Outside of course. See if you can vary the blowing pressure and keep the amount low, make sure it is dry, and see if you can get a bit of a bang.
As for flames, after some practise and study, you can get a reputation for putting your hand into fires and through flames.
I had a very good, experimental undergraduate program at Cornell called Engineering Physics. The name still exists but it is not the 5-year very-intensive (35 credit hours /year about average with dozens of Labs that took many more hours that their "credit hours' suggested) program of my era. Our select group sand cast the metal blanks we would used next year to learn how to operate all types of shop equipment via hands on experience. Later in graduate school that came in handy. I did not need to submit drawing to the physic shop, wait weeks for their turn to come up and get bumped back a week or two by some pprofessor's "URGENT NEEDS" - I did not even make drawings. - I just made metal pieces as I needed.
Once I needed a really flat surface on an aluminum block. Can't get that quickly as heat produced by deep cuts will warp the metal slightly - noticable if they milling machine is good and "running true." So when I had only a mm or so still to remove, I began a series of quick light cuts and accumulated quite a pile of fine Al dust around the block’s base. I was always careful to leave the machine cleaner than I found it (Shop Stewart was not very happy with me doing my own work and I was not going to give him any excuse.) Fortunately, he had gone home when I was done and did not see the three foot flame fly across the milling machine bed when I used the air hose to blow that dust off the machine's bed. That was one thing they forgot to teach about at Cornell.
Once I needed a really flat surface on an aluminum block. Can't get that quickly as heat produced by deep cuts will warp the metal slightly - noticable if they milling machine is good and "running true." So when I had only a mm or so still to remove, I began a series of quick light cuts and accumulated quite a pile of fine Al dust around the block’s base. I was always careful to leave the machine cleaner than I found it (Shop Stewart was not very happy with me doing my own work and I was not going to give him any excuse.) Fortunately, he had gone home when I was done and did not see the three foot flame fly across the milling machine bed when I used the air hose to blow that dust off the machine's bed. That was one thing they forgot to teach about at Cornell.
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