Question

The sides of safety matches contain:
A. red phosphorus + sand powder
B. ${P_4}{S_3}$
C. $C{a_3}\left( {P{O_4}} \right) +$ glass pieces
D. $KCl{O_3},KN{O_3}$ sulphur + antimony

Answer 1

Hint: We know that the head of safety matches are coated with a material that can be ignited by frictional heat generated by striking the match against the sides of it.

Complete answer:
The heads of matches are made of potassium chlorate which is an oxidizing agent, mixed with sulphur , fillers and glass powder. The decomposition of potassium chlorate gives oxygen and potassium chloride. The wood ignited by the catching fire in sulphur. So the head of the match stick contains $KCl{O_3},KN{O_3},$ sulphur and antimony.
The striking surfaces or sides of the safety matchbox contain red phosphorus, powder glass and glue. When the rubbing of safety matches on the striking surface the friction generates enough heat to convert a trace of the red phosphorus into white phosphorus. Thus the immediate reaction of potassium chlorate in the match head produces enough heat to ignite the antimony trisulphide and start combustion. Hence option A is the correct answer to this problem, that is the sides of safety matches contain red phosphorus + sand powder.

Note : We all are aware that matches are made of small wooden sticks or stiff paper. The head of safety matches contains antimony trisulphide, potassium chlorate, sulphur, powdered glass, inert filters and animal glue. It is not possible to ignite antimony trisulphide by the heat of friction. It requires another source of ignition to start the combustion. Hence the source of ignition comes from the striking surface which is the side of the match box or sometimes on the back cover of the matchbox.