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Q & A: Fire

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Most recent answer: 10/22/2007
Q:
what is fire
- David (age 13)
Wauzeka Stueben School, Wauzeka, WI, USA
A:
Fire is the heat and light that come from burning materials. A material that burns is one that can combine quickly with oxygen. Also, many materials that burn have a lot of carbon in them.

There must be certain conditions before fire can occur. First, a substance that can burn, called a fuel, must be present (wood is a good fuel, water is not). Second, there must be a lot of oxygen present (the air, for example). Third, the fuel must reach a temperature where it can easily combine with oxygen. This point is called the kindling point. Once that temperature is reached, watch out! (usually these temps are very high)

Fires get their shapes from the motion of the gases during the burning process. Usually, these gases are heating up, expanding, becoming less dense than the surrounding gas, and rise upwards. The burning can continue in these rising gases, giving off light. Many fires are colored yellow -- the presence of even a small amount of sodium in the burning material will color the fire yellow because sodium atoms prefer to give off that color light. (sodium streetlights are also yellow). Other fires can be other colors -- natural gas usually burns blue. Magnesium burns very very rapidly and emits lots of light. It was used to make flashes of light to take pictures before electronic flashtubes were popular. A very very rapid fire is called an explosion. Fireworks are specially designed explosions with chemical additives to make the burning material glow with different colors.

Interesting fact: Human beings are the only animals that ever created and used fire. Today, fire is widely used to heat water to make steam which is used in engines. It is also used in most homes' furnaces in this part of Illinois to keep them warm. Fire is used in the engines of automobiles, taking advantage of the property that the heated gases want to take up more room than the unheated, unburnt fuel. These push on the pistons of cars in order to push the cars along down the road.

(published on 10/22/2007)

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