Theory:

     Three things are needed to make fire— fuel, oxygen and heat. Wood, coal, cooking gas and petrol are some examples of fuel. Oxygen comes from the air. That is why, when you blow on smouldering paper, it often bursts into flame. The third thing needed to make fire is heat. Fuel and oxygen do not make fire by themselves, or else a newspaper or a stick lying in the open would catch fire on its own. To burn a piece of paper or wood, we heat it before it catches fire. We generally do it with a lighted match. Every fuel has a particular temperature at which it begins to burn. This temperature is called the ‘flashpoint’ or ‘kindling temperature’ of the fuel.
Explanation:

We have seen it in the previous paragraph that we need two ingredients to make fire. They are oxygen and fuel. But there is also a third element that is required. That is heat.

For example, imagine that you are trying to set fire onto a wet paper. Will it catch fire? No. Why is that? It is so because the paper lacks heat. Therefore, heat is essential while creating fire. That is also a reason why it may take more time to start a fire in colder places.
 
Hence, the three components needed to create fire are fuel, oxygen, and heat.
 
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The three things needed while starting a fire
 
Some of the examples of fuel are wood, coal, cooking gas, petrol, and paper. Fuel is the only visible part of the components. Fuel is also the component on which the fire catches on.

Oxygen is found in the air that we breathe. Oxygen is invisible, but it is present everywhere. Fire will never persist without the oxygen.

Heat is the initial stage of fire. For instance, let us look into the following video. When you light a candle using a matchstick, you will discover that it would take some time to catch a fire. However, if you are going to light a candle whose wick is still hot, then the candle will catch fire quickly.
 
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The candle can be lit quickly if the wick is still hot
 
Hence, heat is needed to start a fire. Heat from the sun is also the reason why the forest fire happens. It is also the reason why the roofs of the houses made of dry coconut leaves and straw catch fire during extreme summer.
Not every fuel catches fire at the same time. For instance, fuel such as paper and petrol catches fire quickly than several other kinds of fuel. Hence, every fuel has a particular temperature at which it begins to burn. This temperature is known as the ‘flashpoint. It is also known as ‘kindling temperature’ of the fuel.
S. No
Component
Source/Examples
1
FuelWood, coal, cooking gas, and petrol
2
OxygenAir
3
HeatFire; sun
 
Meanings of difficult words:
 
No.
Words
Meanings
1
SmoulderingThe process of burning slowly with smoke but no flame
2
FlashpointThe lowest temperature at which the material burns in air
3
KindlingStimulating
Reference:
National Council of Educational Research and Training (2007). Honeycomb. Fire: Friend and Foe (pp. 114-118). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.