I watched sodium video. Guy dropped a chunk of it in water and told that it is going to explode. Duh. Had been impressed had they bothered to tell what exactly

I watched sodium video. Guy dropped a chunk of it in water and told that it is going to explode. Duh. Had been impressed had they bothered to tell what exactly was the reaction and why was the heat generated. Instead they laughed, and laughed. btw, I understand basic chemistry so I dont really need explanation.