When I was 10 I discovered how to make black powder and I made it and things to use it with until I was in 8th grade and put away childish things. My younger brothers, as they hit the same age range liked to blow up things, too, and blew up ant beds and such. The youngest discovered what you could do by removing the stuff from the ends of a whole lot of big wooden matches. It was tedious but rewarding.
I thought I was the only one that would be confessing on this thread, but I underestimated FReepers! BTW, the old playing cards, the ones made out of cellulose could be used in a way to make things blow up also. Easier to do than using match heads.
As a point of interest, there was a guy in San Quentin(I believe that is the correct prison)who made a zip gun with a barrel made out of a curtain rod, used rectangular bullets and powered them with match heads. He killed a guard with it during an escape attempt.
This was back in the day and I forget the exact date.
Powdered magnesium on ant hills when I was in sixth grade. Also gunpowder with my Junior Chemistry Set; lot of ants died.
In the 8th grade I had a booming little business selling modified motorcycle spokes bent into the shape of a gun and powered with the tops of matches. Unfortunately, word got back to the principal. Business closed.