Why does fire...?

Question

produce heat, and why does it produce light?

Answer 1

Fire may result from the burning of pure carbon in oxygen to form CO2 (one carbon + two oxygen).  Before combustion the single carbon atom and the two oxygen atoms (often traveling in pairs as a diatomic gas) each had a characteristic energy level (like fuel in a gas tank, etc.).  After combustion, the characteristic energy of the molecule (CO2) is far less than the atoms that make it up and the excess energy is given up as heat (in an exothermic - heat out- reaction).  Other forming molecules require take from the environment because their characteristic energy level is greater than the energy supplied by the atoms in an endothermic - heat in - reaction and there is a cooling effect.

During combustion the excess energy from burning carbon in oxygen is supplied to the electrons orbiting the molecule, kicking them up into higher more energetic orbits.  When the electrons fall back to rest orbits they give up their excess energy as photons (small mass-less packets of pure energy).  The wavelengths of the photons (and their color) depends upon the excess energy and may result in visible light, infrared, ultraviolet or a mixture of light waves.  The spectra of the light waves is used to help identify the chemicals (carbon and oxygen) that have produced the light.  Although the flame may be nearly invisible, unburned carbon atoms (soot) may glow yellow due to the tremendous heat of combustion producing visible light.

Answer 2

Fire results from an exothermic reaction. The end products have less energy than the reactants, and this is emitted as heat.

The light is a consequence of the heat. Some of the energy is absorbed by molecules, and then re-emitted as light.

Answer 3

fire is a chemical reaction that oxidized carbon and other molecules, the result of this oxidation is heat and light (both are different frequencies on the energy spectrum)

Answer 4

The oxidizing chemical reaction, which produces energy, is exothermic. This means it produces heat.

For light, this depends if there are any impurities in the reaction.

Answer 5

It's a visible, tangible side effect of matter changing form -- it's one part of a chemical reaction.

Typically, fire comes from a chemical reaction between oxygen in the atmosphere and some sort of fuel (wood or gasoline, for example). Of course, wood and gasoline don't spontaneously catch on fire just because they're surrounded by oxygen. For the combustion reaction to happen, you have to heat the fuel to its ignition temperature

When the volatile gases are hot enough (about 500 degrees F (260 degrees C) for wood), the compound molecules break apart, and the atoms recombine with the oxygen to form water, carbon dioxide and other products. In other words, they burn

As they heat up, the rising carbon atoms (as well as atoms of other material) emit light. This "heat produces light" effect is called incandescence, and it is the same kind of thing that creates light in a light bulb. It is what causes the visible flame.