Sugar Density Experiment – Rainbow in a Cup

This water density experiment with sugar produces an amazing science experiment for kids.


  • 6 glasses or cups
  • 1 cup measuring cup
  • 1 tablespoon measuring teaspoon
  • Glass jar or plastic bottle
  • Water
  • Sugar
  • Food coloring


  1. Set out 6 glasses. Measure 1 cup of water into each glass. This is a great time to explain the importance of all the glasses having the same amount of water.
  2. Add a few drops of food coloring to each glass of water. You could have your child mix the colors or help them with mixing the colors.
  3. Measure and add a different amount of sugar to each glass of colored water.
  • Red – 2 tablespoons
  • Orange – 4 tablespoons
  • Yellow – 6 tablespoons
  • Green – 8 tablespoons
  • Blue – 10 tablespoons
  • Purple – 12 tablespoons
  1. Stir until as much of the sugar is dissolved as possible.
  2. Please take note that this part of the project takes a slow hand and patience. Starting with the densest water (purple), add the colored water into a glass jar or plastic bottle.
  3. Add the next color very, very slowly. You may want to release the water slowly along the side of the glass jar or plastic bottle.
  4. Continue to do the same thing, working your way back through the colors.

What is happening?

The more sugar you mix into the same amount of water, the higher the density of the mixture. That is why the colored sugar solutions stack on top of each other.

  • Why is density important?
    • Density helps us predict if something will sink or float. Density is super important to consider when building things like ships or submarines.
  • Where can I find density in action?
    • Think about swimming. Did you know that it’s easier to float in the ocean than in a pool? That’s because ocean water is denser than pool water, due to the high salt concentration.