A classic investigation on the density of liquids is explained for you in this lesson plan. Te begin, you prepare water samples of different salinities and then add different food coloring to keep them separated and easily identified. The laboratory procedure is given to you, but you may want to copy it onto a separate page as a handout for your learners. In a nutshell, they carefully pour the samples into cups and examine the layers formed. They are also given unknowns to try to identify.