Fire
Fire
Fire is a rapid oxidation process that creates light, heat, smoke, and releases energy in varying intensities. It is commonly used to describe either a fuel in a state of combustion (e.g., a campfire, or a lit fireplace or stove) or a violent, destructive and uncontrolled burning (e.g., in buildings or a wildfire). The discovery of how to make fire is considered one of humankind’s most important advances, allowing higher hominids to ward off wild animals, cook food, and control their own source of light and warmth. A new theory proposes that there was a direct relationship between mastering fire and a rise of intelligence of higher hominids as a result of the influence of the energy released from fires on the human brain.
Broadly speaking there are two types of fire, flaming and smoldering fires. The former is the rapid oxidation of a fuel (combustion or release of energy) with associated flame, heat, and light. The flame itself occurs within a region of gas where intense exothermic reactions are taking place. An exothermic reaction is a chemical reaction that takes place within a substance whereby heat and energy are released as the substance changes to a simpler chemical form. As chemical reactions occur within the fuel being burned, light is usually emitted as photons are released by the oxidation of the fuel.
Depending upon the specific chemical and physical change taking place within the fuel the flame may or may not emit light. For example, burning alcohol is usually invisible although the heat given off is tremendous. The visible flame has no mass. What we see as visible flame is actually energy (photons) being released in the form of light by the oxidation of the fuel. The color of the flame is dependent upon the energy level of the photons emitted. Lower energy levels produce colors toward the red end of the light spectrum while higher energy levels produce colors toward the blue end of the spectrum. The hottest flames are white in appearance. The color of a fire may also be affected by chemical elements in the flame, such a barium giving a green flame color.
The latter example, a smoldering fire, is a flameless form of combustion, deriving its heat from oxidations occurring on the surface of a solid fuel. Two common examples are glowing coals and cigarettes. Smolder propagates in a creeping fashion over solid fuels or inside porous fuels, and its temperature and heat released are low in comparison. The difference between flaming and smoldering combustion is that the latter occurs on the surface of the solid rather than in the gas phase.
Fires start when both a flammable and/or a combustible material with an adequate supply of oxygen or another oxidizer is subjected to enough heat. The common fire-causing sources of heat include a spark, another fire (such as an explosion, a fire in the oven or fireplace, or a lit match, lighter or cigarette) and sources of intense thermal radiation (such as sunlight, a flue, an incandescent light bulb or a radiant heater). Mechanical and electrical machinery may cause fire if combustible materials used on or located near the equipment are exposed to intense heat from Joule heating, friction or exhaust gas.
Fires can sustain themselves by the further release of heat energy in the process of combustion and may propagate, provided there is a continuous supply of oxygen and fuel. Fires may become uncontrolled and cause great damage to and destruction of human life, animals, plants and property. Fires can also occur through instantaneous combustion. This highly disputed phenomenon is currently under research. It is known that this does occur in a vacuum but is disputed as to whether or not it occurs in nature. This act of combustion leads to an exothermic reaction, which in turn is able to be used as a power source. By harassing this heat from the combustion of coal, wood, petroleum, and oils, we are able to produce power for things such as automobiles, power cells, and power plants.
Humans, since they have “Mastered fire” over the last 170,000 years, are a significant contributor to Global Warming, both through the accidental or deliberate starting of forest fires. The energy transformation process releases CO2 and reduces valuable plant and forest life, disrupting the natural Carbon Cycle.
Information Courtesy of Wikipedia
