Every year at Halloween I demonstrate a combustion reaction in a pumpkin. Adding calcium carbide to water produces acetylene gas. In air, with a spark, the acetylene ignites explosively. I conduct this reaction in a pumpkin that has been pre-carved and the face pieces replaced. It is always exciting for the students - so exciting that they often can't get a good video. Watch.
Step 1: CaC2 + 2 H2O → C2H2 + Ca(OH)2
Step 2: C2H2 + O2 → CO2 + H2O