JokesMarriage Johnny’s Humorous Take On Chemistry Class. Little Johnny’s Chemistry Confusion. Little Johnny’s teacher asks, “What is the chemical formula for water?” Little Johnny replies, “HIJKLMNO”! The teacher, puzzled, asks, “What on Earth are you talking about?” Little Johnny replies, “Yesterday you said it was H to O!” See more Previous joke A Man Was In Hurry To Catch A Train. Next joke A Couple Was Relating Their Vacation Experiences.