what  EXACTLY is fire?
612104
The explanations of fire in most standard reference works, not to put too fine a point on it, suck. The Encyclopaedia Britannica, for example, takes the following ineffectual stab: "rapid burning of combustible material with the evolution of heat and usually accompanied by flame." No wonder people have lost faith in science. Time to let a professional show how it's done. We'll start by reviewing the defects of the EB definition.\n\n(1) Rapid burning. OK, fire burns rapidly. Slow combustion, also known as oxidation, includes such nonfiery processes as rusting and digestion. However, to say that fire involves burning is to embark on a circular definition: What is fire? When something burns. What is burning? When something is on fire. We need to address the matter in more basic terms.\n\n(2) Combustible materials. Redundant. If a material is capable of rapid burning, by definition it's combustible. Also, "materials" is needlessly vague. One specific material, oxygen, is always involved.\n\n(3) Evolution of heat. I don't know what this is supposed to mean either.\n\n(4) Usually accompanied by flame. "Usually accompanied by" my arse. Flame is the quintessential pyrolytic phenomenon, not a mere by-product.\n\nNow for a proper definition, devised by myself: "Fire is the rapid combination of oxygen with fuel in the presence of heat, typically characterized by flame, a body of incandescent gas that contains and sustains the reaction and emits light and heat." Let's go through this bit by bit:\n\n(1) Rapid combination of oxygen with fuel in the presence of heat. Oxygen, fuel, and heat are the essential ingredients of fire. \n\n(2) Typically characterized by flame. The pup qualifier "typically" allows me to sidestep the issue of apparently nonflaming fires, like you get with burning charcoal. I suspect charcoal fires do create flame--you just can't see it due to the lack of impurities or incompletely burned fuel in the plume. (You can't see a fuel fire at an Indy or CART race either, because the cars run on clean-burning methanol.) But that's a matter we can leave for another day.\n\n(3) Body of incandescent gas. Flame defined. Most encyclopedia and dictionary definitions blow past this entirely, allowing persons such as yourself to imagine that fire is "pure energy" or similar nonsense. We say "body" because the gas has a characteristic structure and composition. We say "incandescent" because (a) it sounds scientific, (b) it means "luminous with intense heat," precisely what we are attempting to convey, and (c) if the Teeming Millions are going to learn one vocabulary word today, by God "incandescent" should be it.\n\n(4) Contains and sustains the reaction. Flame isn't just the result of fire; it is the fire. What's more, without the flame's heat the fire would go out.\n\n(5) Emits light and heat. Duh. However, we mustn't overlook the obvious.  \n\n>>>why do things that are put in it come out totally destroyed?\n\nOf course most things that go into fire aren’t totally destroyed. Most metals, glass, ceramic and so forth all emerge unscathed from fire. Even wood and paper aren’t totally destroyed, they leave an ash and charcoal residue as well as fine particles that we can see as soot and smoke.\n\nFire will ‘destroy’ anything organic that can be completely oxidised at the temperature that it burns at, but that is simply because the oxidation process converts the organic material to carbon dioxide,  and water. IOW the material isn’t destroyed it is just converted to gas and that gas blows away.\n\n>>>>>what fuel does it need from say, paper,\n\nThe paper IS the fuel the fire needs. The fire converts the paper into gases and ash. Or more accurately fire is the process of converting paper into gases and ash.
798111
Combustion or burning is a complex sequence of chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames.\n\nIn a complete combustion reaction, a compound reacts with an oxidizing element, and the products are compounds of each element in the fuel with the oxidizing element.
465006
Fire is not matter. The combustible material is a 'solid' like  wood, but can be a 'liquid' like gasoline. The wood combusts, releasing 'gases' such as Carbon Monoxide and solids such as ash particulates. The "fire" is the energy released in the form of heat and light. That's my simple explanation.
669173
Ah, but fire DOES reproduce.  .  .  .\n\n\nThis is a great question.  Astrobiologists tangle with "what is life" question all the time as they try to define just what it is they are looking for.  It is a tough one and last I looked there is no answer that completely satisfieds anyone (much less everyone).  For every definition seems like you can often find something that fits it that is clearly not alive, or something that misses and clearly IS alive (sometimes both!).\n\nOne defintion appears good here, but fire fits the definition quite well as do dust devils!\n\nhttp://www.windows.ucar.edu/tour/link=/earth/Life/life1.html&edu=elem\n\nChrys Chyba of SETI has an online lecture and slide show that discusses this topic in the larger context of searching for life.\nhttp://www.spaceref.com/focuson/seti/10.10.01.chyba.life.html\n\nIf you want to plumb the depths of this issue (defining life) in some detail, there is a very nice paper by a Science Historian/Philosopher with the wonderful title "Why I Stopped Worrying About the Definition of Life... And Why  You Should as Well." \n\nhttp://www.pitt.edu/~machery/papers/Why%20I%20stopped%20worrying.pdf\n\nHe doesn't survey various definitions, but more talks about different approaches to creating definitions and does give a few examples.\n\nAnyway, I don't think of fire as alive, but the overall question of how to exclude something like fire and include everything that is clearly alive is a tough nut to crack that many people have struggled with for a loooong time.
958252
It's when you burn something to offer it to a god or gods, usually on an altar made for this purpose - made of stone and outside.  Many ancient cultures practiced this; it was believed that the smoke rising to heaven and the transformation via fire sent the essence of the grain or lamb or whatever, to the god(s).
772942
that is a very interesting question...i was watching a documentary about that, it sounds incredible but i believe it can be real. One difficult thing to understand is how can fire be created from inside the body..if there is no enough oxygen....besides nothing burns from the inside out.
1182331
Fire is a visible sign of combustion - an exothermic oxidation reaction. \n\nExothermic means that it releases energy.  In the case of visible fire (not all "flames" are visible) some of the energy is radiated at frequencies in the visible light waveband.\n\nBTW: color is related to temperature - "red hot" is around 500 C
140717
Fire is the act of oxidizing fuel.  The hydrogen and oxygen are already bonded, so there's not fuel or oxygen.  Steam is just a state change, not a chemical reaction.
882184
Fire is simply a term that we use to describe a chemical reaction that results in the release of incandescent gas (usually due to the effects of the high temperature of the reaction on the reaction product (gas)).\n\nOrdinary wood fires are not hot enough to create plasma, the fourth state of matter. The sun is an incandescent ball of plasma, so it is technically not "fire" although it may appear to be so. A burning match, while hot, is not nearly hot enough to convert gas into plasma.
868915
Burning is something that happens to solids before they become a liquid and then a gas. The melting, boiling and evaporation points for water prevent it from being burned in any of it's states.
1106185
Are you asking about flame (as in fire), or phlegm (mucous), or what?
422781
I believe the term is SHC or Spontaneous Human Combustion. And unfortunately its a myth. Yes people have been found burnt to death in circumstances where the bones have been turned to ash (which requires 2000deg Centigrade) whereas other parts of their bodies remain virtually intact. Seems highly improbable, doesn't it? \nWell, quite recent studies by "Fire Engineers" (People who study the reaction of fire in different circumstances.) have stated that this occurance though rare is actually scientifically quite possible when cirtain elements come together.\n\n1. You have to have a combustible material that will burn fast at a high temperature. (eg. perfume or other alcohol based substances)\n2. You have to have an element that will sustain this high degree combustion for over an extended time.(eg. certain types of fat_this also explains why the burns are contained in one area or do not move to others on a persons body.)\nAnd:\n3. You have to have a very unlucky accident. (eg.Getting to close to the fire, dropping a ciggarette on yourself....i.e. doing something close to fire that isn't supposed to be done......)\n\nThat's it. The people actually catch fire and burn very HOT very QUICKLY and the fire is CONTAINED IN A CERTAIN AREA.\n\nI hope that's been helpful.
1131939
when referring to a fire burning down:  this is the process of a house fire as it is burning.  It is the action at the time.  The house is burning down.  \nwhen referring to a fire burning up:  this is the end result.  The house has burned up.
422438
According to String theory fire exists in 11 dimensions.  We can only see fire in 3 spatial dimensions and 1 temporal dimension.  When fire goes out, it expands into the dimensions we cannot see where it exists as a high energy plasma.  When you light a match, you are actually opening up a wormhole into those other dimensions.  The fire then expands into the the 3 spatial dimensions we can see.
376297
Flames are the actual oxidation of material, heat is a product of the oxidation. So flames occur as a chemical reaction happens with a combustible. That chemical reaction creates energy, which is given as form of heat. Not all Heat will come from flames.
80193
Mine's gotta be ice - I absolutely love the cold! Fire doesn't really appeal to me (I hate the heat - even from a warm oven, or a burning fireplace). Besides, ice can be scuplted into different shapes (which just proves how incredibly versatile it is).\n\nFire on the other hand is just a flame licking all over the place, burning with passion and searing with heat.\n\nThat of course, is not to say that I'm a cold hearted guy with an icy stare. I just like the ice... =p
42096
Fire is what is called a "redox reaction."  This is where atoms exchange electrons, truning high energy bonds into low energy bonds (or orbitals).  Every redox reaction needs an oxidizer (which takes electrons) and a reducer (which gives up electrons).  In a normal fire, oxygen acts as the electron-accepter.  Carbohydrates (wood, sugar, oil, coal, etc) usually acts as the reducer (ie the electron donor).\n\nO2 takes away electrons and becomes CO2, meaning that the oxygen gets consumed in the burning process.  So really, both the oxygen and the fuel are burning, because they both release energy and end up changed by the process.