When something is lit up, it almost immediately catches fire. Some substances like sodium catch fire without the help of any external source while substances like wood take a lot of heat to catch fire. However, some substances do not burn with a flame, a popular example being coal. But, why does it burn without a flame?

Before we dive deeper, two concepts should be clear- Volatile and Non-Volatile Substances.

Volatile substances are the substances which convert to vapours at the current surrounding temperature and pressure conditions. A popular example is petrol.

On the other hand, non-volatile substances are those which do not convert to vapours at the prevailing temperature and pressure conditions in the surrounding.

A substance will only produce a flame when the substances present in it are volatile. This statement is explained in detail below.

When we burn something, it gets heated up. The substances trapped inside the combustible thing also get heated and, if they are highly volatile, they vaporize and catch fire with the help of the atmospheric oxygen. Thus a flame is produced.

On the other hand, if the substances are non-volatile, the combustible thing will only get heated but will not produce any flame.

So, how was it? Did it heat you up so much that you caught fire? Feel free to comment in the Comments section.

Author: Venkata Bhamidipati

Source of Image: theconversation.com