What is needed for the process of combustion?
• We know that we need a match stick or a lighter to burn a material.
• How will you prove that air is needed to burn a material?
• Can we burn a material in the absence of air?
Types of Combustion:
During summer time, dry grass catches fire in the forests. It may spread to the trees and very soon the whole forest will be on fire. It is very difficult to control such forest fires.
If the head of a match stick is rubbed on the side of a match box, it starts burning.
What makes match sticks to catch fire?
A mixture of antimony trisulphide, potassium chlorate and white phosphorus with some glue and starch was aplied on the head of a match stick made of suitable wood. When it struck against a rough surface white phosphorus got ignited due to the heat of friction. This starts the combustion of the match stick. However, white phosphorus proved to be dangerous both for the workers involved in the manufacturing of match
boxes and for the users.
These days the head of the safety match stick contains only antimony trisulphide and potassium chlorate. The rubbing surface has powdered glass and a little red phosphorus(which is much less dangerous). When the match stick is struck against the rubbing surface, some red phosphorus gets converted into white phosphorus. This immediately reacts with potassium chlorate in the matchstick head to produce enough heat to ignite antimony trisulphide and start the combustion.