A popular thing to give little boys used to be chemistry sets. You could buy them in the toy sections of department stores. Some were pretty extensive and some were very basic. When I was eight I had a cheap one. There wasn't that much I could do with it but it got me thinking.
One of the things it got me interested in was smelting metal. You have to generate a pretty high heat to melt steel, aluminium or even copper. I never got there. I could melt lead though. That was easy. I would pour gasoline into a coffee can that had a lot of holes punched into it a couple of inches up. I'd put in a grate made from coat hangers and place a smaller steel can, like deviled ham came in, on the grate. In the grate I'd put in lead, usually fishing sinkers from my father's tackle box. After I lit up the gasoline, I hooked up the hose to the exhaust vent of my mom's vacuum cleaner and blew across the surface of the burning fuel. It got plenty hot. Lead would melt down right away in that. Then using some kitchen tongs I could take the little can with molten lead and pour it into a sand cast mold. I also thought it was neat to pour it down ant hills. The lead would form a perfect impression of the subterranean ant trails. It would also kill a lot of ants.
Another thing I tried to do was make gun powder. Theoretically it should be pretty simple. It's just sulfur, charcoal and saltpeter, ground fine and mixed. I could never find a recipe of the exact proportions. By experimenting, I could get a fairly volatile mixture but I never got anything that could be termed violently explosive. Probably just as well. One time I took a couple rolls of caps from a toy gun and pried off the dots of gun powder into a plastic medicine bottle. I got a small but significant amount of gunpowder that way. I thought maybe I could make a large firecracker or small bomb with it. It was all lumpy though. I wasn't sure it would work like that. I put the cap on the medicine bottle and shook it up. It worked fine. I couldn't hear anything but a high whine in my head for the rest of the day. I still don't think the hearing in my right ear is as good as the other one. It's a good thing I didn't have my thumb over the cap on the bottle. A fella really gets a lot of use out of his thumbs.