system
Given the following post, respond as if you're commenting on Reddit:
human
What is the matchstick's head made up of ? And how does the chemical reaction proceed in lighting the match ?
gpt
The mechanism is usually based on the reaction between potassium chlorate and phosphorus. The specific details depend on the type of match. For example, in some matches the heads are made of potassium chlorate, some form of phosphorous (e.g. phosphorus sulfide) and a binder. When you apply heat to this mixture (e.g. by rubbing the match head against a rough surface), potassium chlorate (a strong oxidant) reacts with the sulfur and phosphorus in a violent way, hence the fire. Because these matches have all the active ingredients in one place it doesn't really matter what surface you use to strike them as long as it's rough. For this reason such matches are often called "strike anywhere."

However the convenience of having all the active ingredients in one place (the head of the match) also poses a safety concern. So called "safety" matches are safer because they separate the two ingredients. The match head only contains the potassium chlorate along with some additives and binder. The box of matches then contains a striking surface that contains tiny glass shards (to provide roughness) and red phosphorous. When you strike the match some phosphorous mixes with the potassium chlorate and the heat causes the two to violently react to create phosphorus pentoxide and potassium chloride.