What do you think of when you see a rainbow in a glass? My daughter thought “pretty”, I thought about density and concentration, and my husband thought college (granted we were doing the project in a shot glass). At least I was with the lesson plan! By using only sugar, water, and food dye you can do an easy and neat lesson on concentration with your kids (yes, neat).
You’ll need 5 glasses, or 4 glasses and a shot glass (hehe). In the first glass add 1 Tbl of sugar, 2 Tbl of sugar in the second, 3 in the third, and 4 in the 4th. Keep them in order! Now add 3 Tbl of water to each of the four glasses that have sugar in them. Mix. Note: not all the sugar will go in to solution. Now add a few drops of red food coloring to the first glass, yellow in the second, green in the third, and blue in the fourth. Mix again. At this point the first two glasses are probably completely in solution with no visible sugar, the remaining two will continue to have sugar.
Using a syringe (Come on, you mean you don’t have loads of them tucked away from all the various illnesses your child has needed antibiotics for? Just me? Hmpf.) or spoon to carefully layer the water. Start with blue, then green, then yellow, and finally red. If using a shot glass (since “M” was doing the layering I thought the less liquid we had to gently add the better) you only need a few tsp of liquid for each color. Otherwise you want to fill the cup about 1/4 of the way with each color which is why we used the shot glass, less to layer. If you layer carefully enough the colors should remain separated due to the different sugar concentrations of each color. (Note: the colors, several hours later, will mix eventually)
How does it work? By using different amounts of sugar in each glass the concentration was different for each color. The densest solution sits and the bottom and the least dense (least amount of sugar) sits on top. Density is the amount of matter contained in each unit of volume.
***Another interesting density experiment for you to try: cold water is more dense than warm. Dive deeper in to water and how does it feel?