I really did used to believe that if you held a tin tray above a boiling kettle then the moisture that collected on the tray was actually melted tin. I used to spend hours boiling the buggars - and could never understand why the tray got any smaller!
Whats worse is that I even tried to explain this to my mum who just looked at me in bemusement, but never tried to tell me that I was wrong. Is it possible that she believed it too?
A childhood belief about chemistry

others believed things like this
- I used to think what heated the food in the pan was the boiling water, not the heat under it.— Mario
- I used to belive that, when a store held a "liquidation sale", all the unsold stuff would be melted down.— Marty
- while my son was crying one day, my little brother announced that "babies cry to let off moisture". ha!— i'm laughing WITH you
- I used to believe that the rock thing they used in the sport Curling, was a tea kettle.— Kaninchen
- When I was a kid I heard that the Beatles did acid and I wondered if they melted from it.Anon
- i used to say 'our father, who art in heaven, hello whats your name?'— lou