Fire is dangerous. It can reduce an entire forest or a house to a pile of ash and charred wood. But at the same time, fire is extraordinarily helpful. It gave humans the first form of light and heat which enabled us to cook, forge metal tools, and harden bricks. It is certainly one of the most important forces in human history. But what is it, exactly?
In this lesson, we will discuss
Greek philosophy supposed the Universe to comprise four elements: Fire, Water, Earth, and Air. Even though you can feel, smell and move fire just like you can do to water, earth and air still, fire is something completely different.
Earth, water, and air are all forms of matter because they are made up of millions and millions of atoms collected together. Fire isn't 'matter' at all. It is a visible, tangible side effect of matter changing form - it is one part of a chemical reaction.
This chemical reaction is COMBUSTION.
Fire Triangle
The fuel must be heated to its ignition temperature for combustion to occur. The reaction will keep going as long as there is enough heat, fuel, and oxygen. This is known as the fire triangle.
The fire triangle illustrates the rule that in order to ignite and burn, a fire requires these three elements. The fire is prevented or extinguished by removing any one of them. A fire naturally occurs when the elements are combined in the right mixture.
Have you ever seen fire changing color?
Well, fire gets its color from two things - temperature and chemical reaction (combustion).
As we learned earlier, for combustion to occur, the fuel must reach its ignition temperature, and combustion continues when there is enough fuel, heat, and oxygen. Once the temperature gets hot enough for the chemicals in the fuel to react with oxygen, it results in a colorful reaction.
Red color flame is the coolest flame and the orange color represents scorching temperatures.
In the case of a wood fire, the colors also come from the substances burning within the flames.
Structure of flame
A candle flame has different zones within it. There are three main zones - yellow, blue, and dark zone. The yellow and blue zones are the flame.
The wick is designed to curve so that the flame ends at the wick and limits the height of the flame.
Let's take a minute to understand how the flame burns.
The heat of the flame melts the wax. The melted wax soaks the wick by capillary action, evaporates and becomes gas to diffuse into the luminous zone where it finds oxygen. Gas molecules fragment and rejoin with oxygen as combustion takes place.
The heat of the flame melts the wax; the melted wax soaks the wick (by capillary action), evaporates and becomes gas to diffuse into the luminous zone where it finds oxygen. Gas molecules fragment and rejoin with oxygen as combustion takes place. This process is sustained by the constant supply of heat. The temperature of the blue part of the flame has to be more than 1,300°C to sustain the reaction.
If a saucer is kept above the flame, the bottom becomes black. These Black particles which are collected on the saucer are unburnt particles due to incomplete combustion from the wax and are known as soot.
Uses of fire
The early discovery of fire had numerous benefits for early humans. They were able to protect themselves from the weather and were also able to devise an entirely new way of hunting. Evidence of fire has been found in caves, suggesting it was used to keep warm.
In modern times, the common uses of fire are:
