I knew different things happened at different temperatures, but I didn't know the difference between Celsius and Fahrenheit. So if water boiled at 100 degrees, and if you had a fever of 102 degrees, that meant you were sick because you were above boiling.
A childhood belief about chemistry

others believed things like this
- i used to think that only men could get bachelors degrees. i thought women got bachelorettes degrees.Anon
- I used to believe that if you turned the thermastat temperature above 70 degrees that everything would melt.Anon
- I used to think what heated the food in the pan was the boiling water, not the heat under it.— Mario
- I thought that hydrogen was pure water (since I knew hydro- meant water) and H2O was impure some how— Hexetic
- I didn't understand about boiled eggs until my Mum explained I wasn't supposed to eat the shell as well.— Chris
- I used to believe that tapioca was made from boiled used kleenex.— Abby