When I was really young, I used to lock myself in the bathroom and mix together toothpaste, mouthwash, soap, ...whatever, thinking I was doing chemistry and I was going to discover some whole new compound no one has ever seen. Generally I just made a mess in a Dixie cup, but the good news is that I did end up with Ph.D. in Biology, so it wasn't a total loss.
A childhood belief about chemistry

others believed things like this
- For some reason I used to believe humans were made out of toothpaste— lu
- I generally believed in happy endings!— Claire
- if you eat toothpaste straight from the tube, you will get worms— wormelow
- I used to believe that aliens would come and take me if I wasn't good to my parents— somebody
- My Mother used to tell me only the good die young and I would live to be 100+ years old because I was bad.— William
- I was told as a kid that if you kept stuffing a Big Buddies (bubble gum)I would get lock jaw.— Dawn