What is it ? Why does it have colors ?
It is very simple; if a matter is colored, then its absorption of light is in the visible range. A red matter seems red, since the yellow component in white light is absorbed by the matter and the remaining red light is given out. The phenomenon is also known as "complementary colors".
But I see it green when still and orange when angered by wind!
Are human perceptions on colors of fire are different from each other ? If so, why ?
When atoms (mostly metals) and compounds are heated to very high temperatures, the electrons can jump energy levels. When the electrons fall back to their original energy levels, they release a photon at a specific wavelength. When burning carbon things, you get different color flames based on the temperature. Higher temperature allows the electrons to jump higher levels, and therefore emit higher energy photons. Ever notice that blue flame is hotter than yellow flame, and yellow flame is hotter than red flame? Higher temperature means the electrons can jump up more levels, which means they also fall down more levels to release photons with more energy; higher energy photons have a shorter wavelength such as that of blue light. Fires that are unbelievably hot can actually be invisible because the majority of the light is in the ultraviolet range.
Wood and paper are made of a whole bunch of things, so you can't expect them to give any specific wavelengths, but if you expose metals to flame, you get very distinct wavelengths emitted. Sodium burns bright orange/red, strontium is red, barium is white, potassium is purple, and the list goes on. It all has to do with the energy levels of each specific metal.
it all depends on what is in the thing you are burning. copper burns green because the photons given off are at the wavelength that you see as green. temp. also plays its little part (as ShawnD said before)
then what is fire??? ya things burn, ya things glow as embers, but what really makes fire.. no i don't want a specific heat of combustion explanation, nor do i wanta " molecular dissasembly type explanation, but why do coals glow hotter adn fire burn towards new fuel as if it knows that a combustable material is close by... maybe this is bringing back memories of whats that called, phlogostrom
The color of coals are due to blackbody radiation thus are related to their temperature.
The flames get color from the chemical content of the material being burned. Flames are vapors created by the volatile materials in the fuel as they escape to the atmosphere. As the volatile materials vaporize the atoms of the constituent chemicals are left in an excited state. The colors emitted correspond to the states of the excited electrons as they relax to lower energy levels.
Please note that Hypata's link is of historical interest only, phylogsten does not figure into modern understanding.
I had only slightly recalled phylogsten in the context of the evolution of alchemy. Looking back on how conclusions were made, and how the mind thinks, you can almost see the progression to "modern" science.
Separate names with a comma.