Rainbow Water Stack

Our rainbow has a science twist, so you can learn about liquid density. You’ll just need water, sugar, and food coloring.

Step 1: Use food coloring to color equal amounts of water (about ⅓ cup) in the seven visible colors of the rainbow (red, orange, yellow, green, blue, indigo, and violet).

Step 2: Add six tablespoons of sugar to the violet water, five tbsp of sugar to the indigo water, four tbsp to the blue water, and so on (the red water won’t get any sugar at all)

Step 3: Stir vigorously until the sugar dissolves.

Step 4: Carefully use a dropper or a pipette to layer the colored waters, in order from most sugar (on the bottom) to least. You can also use a straw as a pipette to slowly build up the layers and avoid them mixing together.

Step 5: Display your liquid rainbow in the window for all to see!

The colored waters stay separate because of their different densities. As more sugar is added, the molecules in the water solution become denser or more crowded. Denser liquids will sink or settle nearer the bottom, and less dense liquids will float or stack on top.

Are there other liquids around your house that you think could layer because of their different densities? Make a prediction and then try them out (after seeking permission, of course!).