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 Husband And Wife Were Having Dinner. Next joke Kids Are Painting Eggs For Easter.