Name: Combustion: Burning of Substances
Uploaded: 2019-07-19
Duration: 9 min 40 s
Description: You may have seen a bonfire in the cold season, but do you know why the wood in the bonfire starts burning when we heat it? Let's explore.

Question

Write the name of the material that can burn. Grade them in the order of speed at which they will burn.

Accepted Answer

Most of the materials around us can be burnt when they are introduced to heat. But some materials burn more easily and faster than others. Materials which burn easily are called combustible materials and materials that do not burn easily are called non-combustible materials. Paper, wood, coal, clothes, dry leaves are the materials that can burn. They are combustible because they catch fire easily. Water and glass are non-combustible substances.

The speed of oxidation (combustion) of a material is dependent upon several factors, including but not limited to the surface area of exposed material, available oxygen, moisture content and heat of combustion. All three of these materials can be caused to burn at a faster or slower rate than each other by varying their properties.

In the case of dry leaves, no moisture content is present and thus, it catches fire easily and rapidly. The green leaves become dry when all the moisture content is lost from it. So, the dry leftover part of the leaf has stored fuel energy in it and which is released in the form of heat when it catches fire.

Cotton fabric does not shrink or melt on burning. It gets converted into ash on burning. It smells like a burning paper because both cotton fabric and paper are obtained from plants. Paper by itself catches fire easily because it has low ignition temperature.

Being far denser than wood, coal burns more steadily and longer.

Thus, the increasing order of their speed of burning is given as:

Coal $<$ Wood $<$ Paper $<$ Clothes $<$ Dry leaves

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