The striking surface of a matchbox is made of sand, powdered glass and red phosphorus. A match head contains powdered glass, potassium chlorate, sulphur and gelatin. When the match head is struck against the matchbox, the sand and powdered glass cause friction and heat, and this converts some of the red phosphorus to white phosphorus. This chemical is so volatile that it ignites in the air. The heat also breaks down the potassium chlorate in the match head, which releases oxygen. The oxygen combines with sulphur and keeps the flame burning. The gelatin acts as glue to keep everything together in the match head, and also provides extra fuel. What are the energy changes that occur in these reactions ?