Difference between revisions of "Fire" - New World Encyclopedia

Revision as of 17:52, 20 December 2005

From scientific inquiry and technological innovation to philosophical and religious thought, fire has played an enormous role in the development of human civilization. Ancient philosophers considered fire as one of the fundamental "elements" of nature, while religious thinkers regarded the heat and light of fire as metaphors for God's love and truth, respectively. When a fire rages out of control, it can be very destructive, damaging property and claiming lives. But humans have learned to tame fire and use it for numerous beneficial purposes. Today we use fire to cook food, heat our homes, run engines, and drive industrial processes and power plants. Unfortunately, people have also used fire for destructive purposes, as in cases of arson and warfare.

A large bonfire

What is fire?

Log in fireplace

When we see a piece of wood burning, with flames leaping and smoke rising, we say that the wood is "on fire." But what is fire? In general terms, fire is a high-temperature chemical reaction in which a fuel rapidly reacts with an oxidizing agent to generate heat, light, and a variety of products. In other words, fire is not matter itself, but it is the interaction of some forms of matter (such as hydrocarbons and oxygen) at a relatively high temperature to generate other forms of matter (such as carbon dioxide and water) and energy (heat and light).

The fuel may be a solid (such as wood or paper), a liquid (such as oil or gasoline), or a gas (such as hydrogen or natural gas). The oxidizing agent is usually oxygen. Gasoline and natural gas are mainly composed of hydrocarbon molecules, while wood and paper contain long-chain carbohydrates (such as cellulose). When these fuels are burned in oxygen, the main products are carbon dioxide, water vapor, and carbon particles. If the fuel contains nitrogen and sulfur, we get oxides of these elements as well.

Some fires occur in the absence of oxygen. For instance, hydrogen can burn in chlorine to produce hydrogen chloride (HCl). Other possible combinations that produce flames include hydrogen and fluorine or hydrazine and nitrogen tetroxide.

It takes a spark to start a fire. In scientific terms, the fuel—when surrounded by the oxidizing agent—needs to be heated until it reaches a temperature known as its ignition point. While it may seem like a handicap to someone trying to start a fire without a source for a spark, this requirement has a protective effect, considering how dangerous it would be if most fuels could burst into flames simply by being exposed to air at ordinary temperatures. [Some extremely flammable fuels have a low ignition temperature and are therefore stored in air-tight containers away from oxygen.]

At the ignition temperature, some of the fuel is converted to flammable gases, which then react with the surrounding oxygen gas. Once started, the fire usually generates sufficient heat to sustain itself until the available fuel or oxygen is used up. But if the heat generated by combustion does not keep the temperature at or above the ignition point, the fire will die out.

Some chemicals called accelerants can be used to spread fire faster or have it burn hotter. Common accelerants are hydrocarbon-based fuels, including gasoline, diesel fuel, kerosene, turpentine, and butane.

To put out a fire, one has to do at least one of two things: (1) cool the reacting matter until the temperature falls below the ignition point, or (2) prevent the oxygen (or other oxidizing agent) from contacting the fuel. Cooling the reaction is usually accomplished by pouring cold water on the burning matter. Alternatively, one can use a fire extinguisher to spray nonflammable material onto the fuel, thereby smothering the fuel and cutting off the oxygen supply. A third alternative – removing the fuel from the site of combustion – is usually not practical, as the fuel may be too hot or difficult to move.

The flame

The flame consists of gases, solid particles, heat, and light. The bright red-orange color of a flame is attributable to the presence of solid particles (mainly carbon) that have been heated to incandescence. These solid particles form the soot emitted by the fire. The flame also derives part of its light from gas molecules, when some of their electrons undergo transitions from higher to lower energy levels.

"A large flame from propane burners is used to inflate a hot air balloon.

The color of the flame depends on its chemical composition, the temperature of combustion, and the extent of combustion of the fuel. Take the example of a Bunsen burner that burns methane gas, using oxygen from the air. If we restrict the amount of oxygen that mixes with the gas, the combustion is incomplete and we get a yellow flame at roughly 1,000 C. As additional oxygen is allowed to mix in, the extent of combustion increases, and the flame turns increasingly blue. The blue part of the flame is around 1,600 C. By comparison, the flame temperature of a blowlamp can be 1,300 C and that of a candle can reach 1,400 C. An oxyacetylene combustion can be as hot as 3,000 C.

Generally speaking, a red flame is relatively cool. As the flame's temperature increases, its color turns to orange, yellow, white, violet and blue, and bright blue. For a given region of a flame, the closer it gets to white, blue, or bright blue, the hotter that region is.

In addition, when salts of different metals are heated in the flame of a Bunsen burner, they produce specific colors in the flame. For instance, sodium salts produce a yellow flame, potassium salts give a violet color, and copper salts make the flame green or blue-green.

Usefulness of controlled fire

File:Gas burner on stove.jpg

Small open fire

Learning to control fire was one of the first great achievements of hominids. Some studies in archaeology indicate that the hominid species Homo erectus may have used controlled fire as early as 790,000 years ago. Other evidence from the site named the "Cradle of Humankind" in South Africa suggests the controlled use of fire more than a million years ago. But reliable means of starting a fire—such as by the use of wooden drills or flintstones—has been traced to the Neolithic age, around 7000 B.C.E.

For early peoples, wood fires were the main energy source. The ability to control fire enabled them to cook food—a decisive step in the fight against disease—and to migrate to colder regions of the world. Controlled flames also offered a means of lighting dark places. Another use of fire was in long-distance communication through smoke signals.

By the time of the Neolithic introduction of grain-based agriculture, people the world over used fire as a means to clear fields, produce fertilizer (by burning trees and grasses), and manage landscapes. For instance, controlled fires helped clear the undergrowth in forested areas, thereby facilitating hunting and improving the yield of root and berry crops. Fire was also used to clear travel lanes.

A blacksmith's fire, used primarily for forging iron.

Later, fire enabled advances in metallurgy, such as smelting and forging, and alchemists used fire to discover and perform a variety of chemical reactions. That type of work contributed to the foundations of our modern technological society. Today, the energy needs for our homes, offices, industries, agriculture, and means of transportation rely, for the most part, on the burning of fuel, either directly or indirectly.

When we use electricity, we do not burn fuel on site, but most of the world's electricity is generated by power stations that burn coal, oil, or natural gas. At a power station, fire is used to heat water, creating steam that drives turbines. The turbines are linked to an electrical generator. In most developing countries and remote areas, however, wood continues to be the primary energy source.

There is also a long history of the use of fire in warfare. Homer detailed its use by Greek commandoes who hid in a wooden horse to enter Troy and burn the city during the Trojan war. A more recent example is the use of napalm, consisting of gasoline jelled in aluminum soaps, to disable, kill, and destroy infrastructure.

Fire in philosophy and religion

In Greek mythology, Prometheus was the Titan honored chiefly for stealing fire from the gods in the stalk of a fennel plant and giving it to mortals for their use. On a more mundane level, Greek philosopher Empedocles proposed, in the fifth century B.C.E., that fire was one of four unchanging elements that were the basic constituents of all material things. The other three elements he proposed were air, water, and earth. For the ancient Chinese, there were five basic elements: fire, water, earth, metal, and wood. The modern concept of elements was not formulated until the seventeenth century, when Robert Boyle defined them as material substances that could not be broken down into simpler substances.

Fire also plays an important role in the symbolism and rituals of many religions. In Hinduism, fire is regarded as one of five sacred elements that make up all living creatures and as an eternal witness essential to sacred ceremonies. The Zoroastrian religion considers fire as a symbol of the invisible God, or Ahura Mazda, and each temple—called a fire temple—maintains a holy flame. In Judaism, believers light candles to usher in holidays, separate Shabbat from the rest of the week, and remember the dead. The Jews also had the tradition of maintaining an Eternal Flame in the First and Second Temple.

Christians regard fire as a symbol of the Holy Spirit, but they also point to Biblical verses that prophesy a time when the world will be judged by fire (IIPet.3:12; Mal.4:1). The Divine Principle of the Unification movement refers to the prophet Jeremiah's words when he likened fire to God's Word (Jer. 23:29), and it offers the interpretation that "judgment by fire" is a metaphor for judgment by God's Truth.

Uncontrolled fire

File:Wohnhausbrand.JPG

A house on fire

In early geological history, fires started by lightning strikes and volcanic eruptions shaped the Earth and helped prepare the environment for habitation by a huge diversity of life forms.

In today's world, wildfires are extremely dangerous, as they swiftly consume forests, grasslands, and manmade structures, and severely injure living things through burns or smoke inhalation. In the long run, however, these fires also have certain beneficial effects. They thin out forests, free up nutrients from wood, and encourage vegetation that depends on regular burns for survival. Knowing the role of fire in ecosystems, forest rangers may use "prescribed burns" to reduce the hazards of undergrowth and dead fuels.

Structure fires can be started by cooking accidents, electrical faults, fuel leaks, children playing with lighters or matches, and accidents involving candles and cigarettes. Fire can propagate rapidly to neighboring structures, especially when proper building standards are not met. Purposefully starting destructive fires constitutes arson and is a criminal offense in most jurisdictions.

Given the destructive capacity of fire, most municipalities offer firefighting services to quickly extinguish fires. Trained firefighters use fire trucks, fire hydrants, and an array of other equipment to combat the spread of fires.

Uncontrolled fires have been classified according to different systems. In the United States, they are classified into four groups, as folows.

Class A: Fires that involve flammable solids such as wood, cloth, rubber, paper, and some types of plastics.
Class B: Fires that involve greases, flammable liquids (including gasoline, oil, and paint), and flammable gases (such as natural gas and propane).
Class C: Fires that involve any of the materials found in Classes A and B, but with the presence of any electrical appliances, wiring, or other electrically energized objects in the vicinity of the fires.
Class D: Fires that involve combustible metals, such as sodium, magnesium, and potassium.

Occasionally, a fifth group, Class K, is added. It refers to fires involving large amounts of grease or oil. Although Class K is a subclass of Class B, the special characteristics of these types of fires are considered important enough to recognize.

A forest fire

In Europe and Australasia, six groups are used:

Class A: Fires that involve flammable solids such as wood, cloth, rubber, paper, and some types of plastics.
Class B: Fires that involve flammable liquids or liquefiable solids such as petrol/gasoline, oil, paint, some waxes and plastics, but NOT cooking fats or oils.
Class C: Fires that involve flammable gases, such as natural gas, hydrogen, propane, and butane.
Class D: Fires that involve combustible metals, such as sodium, magnesium, and potassium.
Shock Risk (formerly known as Class E): Fires that involve any of the materials found in Classes A and B, but with the presence of any electrical appliances, wiring, or other electrically energized objects in the vicinity of the fires, with a resultant electrical shock risk if a conductive agent is used to control the fire.
Class F: Fires involving cooking fats and oils. The high temperature of the oils when on fire far exceeds that of other flammable liquids making normal extinguishing agents ineffective.

External links

Sources of light / lighting:
Natural/prehistoric light sources:	Bioluminescence \| Celestial objects \| Lightning
Combustion-based light sources:	Acetylene/Carbide lamps \| Candles \| Davy lamps \| Fire \| Gas lighting \| Kerosene lamps \| Lanterns \| Limelights \| Oil lamps \| Rushlights
Nuclear/direct chemical light sources:	Betalights/Trasers \| Chemoluminescence (Lightsticks)
Electric light sources:	Arc lamps \| Incandescent light bulbs \| Fluorescent lamps
High-intensity discharge light sources:	Ceramic Discharge Metal Halide lamps \| HMI lamps \| Mercury-vapor lamps \| Metal halide lamps \| Sodium vapor lamps \| Xenon arc lamps
Other electric light sources:	Electroluminescent (EL) lamps \| Globar \| Inductive lighting \| Discrete LEDs/Solid State Lighting (LEDs) \| Neon and argon lamps \| Nernst lamp \| Sulfur lamp \| Xenon flash lamps \| Yablochkov candles

bg:Огън ca:Foc cs:Oheň cy:Tân da:Ild de:Feuer eo:Fajro es:Fuego et:Põlemine fi:Palaminen fr:Feu he:אש id:Api io:Fairo it:Fuoco ja:火 ko:불 nl:Vuur pl:Ogień pt:Fogo sr:Ватра simple:Fire sv:Eld zh:火

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

Fire ^history
Flame ^history

The history of this article since it was imported to New World Encyclopedia:

History of "Fire"

Note: Some restrictions may apply to use of individual images which are separately licensed.

@@ Line 5: / Line 5: @@
 ==What is fire?==
 [[Image:Log in fireplace.jpg|thumb|250px|Log in fireplace]]
-When we see a piece of [[wood]] burning, with flames leaping and smoke rising, we say that the wood is "on fire." But what is fire? In general terms, fire is a [[chemical reaction]] in which a [[fuel]] rapidly reacts with an oxidizing agent to generate [[heat]], [[light]], and a variety of products. The [[fuel]] may be a [[solid]] (such as wood or paper), a [[liquid]] (such as oil or gasoline), or a [[gas]] (such as hydrogen or natural gas).
+When we see a piece of [[wood]] burning, with flames leaping and smoke rising, we say that the wood is "on fire." But what is fire? In general terms, fire is a high-temperature [[chemical reaction]] in which a [[fuel]] rapidly reacts with an oxidizing agent to generate [[heat]], [[light]], and a variety of products. In other words, fire is not matter itself, but it is the interaction of some forms of matter (such as [[hydrocarbon]]s and [[oxygen]]) at a relatively high temperature to generate other forms of matter (such as [[carbon dioxide]] and [[water]]) and energy (heat and light).
-The oxidizing agent is usually [[oxygen]], but it could also be [[chlorine]] or [[fluorine]]. For instance, [[hydrogen]] can burn in [[chlorine]] to produce [[hydrogen chloride]] (HCl). Other possible combinations that produce flames  include [[hydrogen]] and [[fluorine]] or [[hydrazine]] and [[nitrogen tetroxide]].
+The fuel may be a [[solid]] (such as [[wood]] or [[paper]]), a [[liquid]] (such as [[oil]] or [[gasoline]]), or a [[gas]] (such as [[hydrogen]] or [[natural gas]]). The oxidizing agent is usually [[oxygen]]. Gasoline and natural gas are mainly composed of hydrocarbon molecules, while wood and paper contain long-chain [[carbohydrate]]s (such as [[cellulose]]). When these fuels are burned in oxygen, the main products are carbon dioxide, water vapor, and [[carbon]] particles. If the fuel contains [[nitrogen]] and [[sulfur]], we get [[oxide]]s of these [[element]]s as well.
-Many fuels, such as gasoline and paraffin wax, are mainly composed of [[hydrocarbon]] molecules, which contain [[carbon]] and [[hydrogen]] atoms. Others, such as [[wood]], contain large [[carbohydrate]] molecules (such as cellulose) that in turn are made up of [[carbon]], [[hydrogen]], and [[oxygen]] atoms. When these fuels are burned, the products include [[carbon dioxide]], [[water]] vapor, and [[carbon]] particles.
+Some fires occur in the absence of oxygen. For instance, [[hydrogen]] can burn in [[chlorine]] to produce [[hydrogen chloride]] (HCl). Other possible combinations that produce flames include hydrogen and [[fluorine]] or [[hydrazine]] and [[nitrogen tetroxide]].
-To start a fire, the [[fuel]] usually needs to be heated until it reaches a temperature known as its ''ignition point.'' At that temperature, some of the [[fuel]] is converted to flammable gases, which then react with the surrounding oxygen gas. Once started, the fire usually generates sufficient heat to sustain itself until the available fuel or oxygen is used up. But if the heat generated by combustion does not keep the temperature at or above the ignition point, the fire will die out.
+It takes a spark to start a fire. In scientific terms, the fuel—when surrounded by the oxidizing agent—needs to be heated until it reaches a temperature known as its ''ignition point.'' While it may seem like a handicap to someone trying to start a fire without a source for a spark, this requirement has a protective effect, considering how dangerous it would be if most fuels could burst into flames simply by being exposed to air at ordinary temperatures. [Some extremely flammable fuels have a low ignition temperature and are therefore stored in air-tight containers away from oxygen.]
-Some chemicals called ''accelerants'' can be used to spread fire faster or have it burn hotter. Common accelerants are [[hydrocarbon]]-based [[fuel]]s, including [[gasoline]], [[diesel fuel]], [[kerosene]], [[turpentine]], and [[butane]].
+At the ignition temperature, some of the fuel is converted to flammable gases, which then react with the surrounding oxygen gas. Once started, the fire usually generates sufficient heat to sustain itself until the available fuel or oxygen is used up. But if the heat generated by combustion does not keep the temperature at or above the ignition point, the fire will die out.
+Some chemicals called ''accelerants'' can be used to spread fire faster or have it burn hotter. Common accelerants are hydrocarbon-based fuels, including gasoline, [[diesel]] fuel, [[kerosene]], [[turpentine]], and [[butane]].
+To put out a fire, one has to do at least one of two things: (1) cool the reacting matter until the temperature falls below the ignition point, or (2) prevent the oxygen (or other oxidizing agent) from contacting the fuel. Cooling the reaction is usually accomplished by pouring cold water on the burning matter. Alternatively, one can use a [[fire extinguisher]] to spray nonflammable material onto the fuel, thereby smothering the fuel and cutting off the oxygen supply. A third alternative – removing the fuel from the site of combustion – is usually not practical, as the fuel may be too hot or difficult to move.
 ==The flame==