What makes some chemical reactions explode?

The answer

Explosions occur when a chemical reaction releases an enormous amount of energy faster than the surroundings can absorb it. The key ingredients are rapid gas production, intense heat, and confinement. In an explosive like TNT, the detonation wave travels at about 6,900 meters per second, converting the solid into hot gases that expand to occupy over 1,000 times the original volume almost instantaneously, creating a devastating shockwave.