Combustion and Flame

Flame and Structure of a Flame

Have you ever seen a flame? Actually seen it keenly? If you have you will notice the various colors in it, the unique shape it takes, its mesmerizing movement. Let us take a closer look at flames and the various types of flames.

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What is a Flame?

The word “flame’ itself comes from the Latin word “flamma”. Very simply put flames are the visible part of a combustion reaction. During combustion, the fuel reacts with the oxygen and produces a huge amount of heat energy. Due to this heat, the atoms of the reactants get superheated. And as these atoms are leaving the combustion zone they bleed of this excess energy in form of light.

Now as you saw to see flames some combustion reaction must occur of a fuel in presence of oxygen. A fuel is any substance that is burned as a source of heat or a source of power. Some examples of a fuel are coal or petrol or natural gas. The wax of a candle is also a fuel actually. An ideal fuel is one that is inexpensive and easily available with a high calorific value.

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Understand the Flame of a Candle

Structure of a Flame

Let us now understand the structure of flames with the context of the flames of a candle. For this, you will need to closely observe the flames of an ordinary candle. You will notice its shape, the way it burns and most importantly the various colors of the flames.

When you light a candle a combustion reaction takes place with the wax of the candle which is the fuel and the air which contains oxygen. The flames are the are in which this combustion reaction is taking place. The release of heat and light energy from this exothermic reaction happens through the flame.

Now if you observe you will see three distinct colors in the flames. This helps us to classify the parts of a flame which are as following:

  • Inner Part: This is the innermost part of the flame. It is the part closest to the wick. You might assume that this is the hottest part of the flame. However, it is the least hot. This is the black part of the flames that contains unburnt particles of the carbon from the wick i.e. unburnt fuel.
  • Middle Part: This is the biggest part of the flame. The colors in this are varying shades of yellow and orange. This is the luminous flame because it emits light. This part is also not extremely hot. This is because this part gets a limited supply of oxygen. So incomplete combustion takes place here. Which is why it burns orange and is luminous.
  • Outer Part: Now this is the hottest part of the flame. This part has an unlimited supply of oxygen. So complete combustion takes place here. Hence it is the hottest part of the flame. Also, this part of the flames burns with a blue color. It is the non-luminous, i.e. does not emit light

Solved Question for You

Q: The substances which vapourize during burning, give flame. True or False?

Ans: This statement is False. Not all substances produce flames when burning. Some substances produce Smoke. An example of this is the process of burning charcoal.

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