Have you ever tried making a Rainbow in a Jar project? If you haven't tried this classic density experiment, I'm going to show you how easy it is to make with a few common household items! This rainbow science experiment is so pretty and will amaze your preschool, pre-k, kindergarten, first grade, 2nd grade, 3rd grade, 4th grade, 5th grade, and 6th grade students. Try this rainbow experiment as part of a weather theme, St Patricks Day activity, a rainbow theme or a spring activity for kids.