Coal and petroleum

Coal and Petroleum:

• We all know that petroleum is required to run our vehicles and LPG cylinders are used in the kitchen to cook food. These both are examples of fuels.
• Fuels are the materials which have energy stored inside them so when they are burnt, this energy is released in the form of heat . This energy serves a lot of purposes like in motor cars, for cooking food etc.
• When carbon in any form (charcoal, coke etc.), is burned in oxygen, it releases CO 2 gas and a large amount of energy in the form of heat and light .

Why do some substances produce a flame on burning and some do not?

• If we burn wood or coal , it can be observed that they do not produce a flame , rather glow and produce some heat . 
• On the contrary, we can see that the LPG gas above the cylinder  produces a flame when burnt . 
• This is because flame is produced only when gaseous substances burn. When wood or charcoal is burnt, the volatile substances present in them vapourize and burn with a flame in the beginning.

When the atoms of gaseous substances are heated, they glow and produce a dazzling bright flame. The color p roduced by each element is the characteristic property of each elemen t.

Fo rmation of Coal and Petrol eum:

1. Coal:

The decomposition of large land plants and trees buried under the earth for several million years leads to the formation of coal.

2. Petroleum:

 Petroleum is formed by the decomposition of extremely small plants and animals buried under the sea for several million years. 

Why do they cause pollution?

Coal and petroleum contain nitrogen and sulfur in them. Therefore, when these fuels are burnt, they lead to the formation of oxides of nitrogen and sulfur which go into air and cause pollution .