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Sugar Water Density Experiment

What happens when you combine blue, green, yellow, and red water in a single glass? Brown, right? Not necessarily! Make this mesmerizing rainbow-in-a-glass by fiddling around with water density.

Density measures the amount of mass in a particular space. For example, oil molecules are packed less tightly than water molecules, making oil less dense than water and causing it to float on top when the two are combined. Water can have different densities as well. An easy way to change water density is with sugar. When you mix sugar with water, the sugar molecules occupy the space in between the water molecules, making the solution more tightly packed (denser). The more sugar you add, the denser the solution.

In this sugar water density experiment, we will change the density of different colored water solutions so that they stay separated from each other. All you need are a few common household items, listed below.


  • 5 glasses
  • warm water
  • sugar
  • spoon
  • food coloring
  • syringe

How to Conduct the Sugar Water Density Experiment

1. Fill four glasses with 1/4 cup of warm water each.

2. Add sugar and food coloring. Each color will have a different amount of sugar in it.

Glass 1: Add 1 tbsp of sugar and 2 drops of red food color. Stir vigorously to completely dissolve the sugar.

Glass 2: Add 2 tbsps of sugar and 2 drops of yellow food color. Stir vigorously.

Glass 3: Add 3 tbsps of sugar and 2 drops of green food color and stir.

Glass 4: Add 4 tbsps of sugar and 2 drops of blue food color and stir.

NOTE: Stirring to completely dissolve the sugar is very important; without the sugar fully incorporated into the water, you’ll have trouble getting the colors to separate. Heat up your water more if it’s not working – 5 to 10 seconds in the microwave and an extra stirring session should help.

3. Use the syringe to transfer about half of the blue water into the empty glass. This is where you’ll make your rainbow.

4. Still using the syringe, transfer half the green water into the rainbow glass. Add it slowly on top of the blue water. It should sit on top.

5. Add the yellow, and then the red. You’ll see a beautiful rainbow!

NOTE:  Make sure the sugar is completely dissolved before attempting to layer the colors – it’s what creates the difference in density of each color.

Bring on the science!

During this activity, natural questions may come up.  If they don’t, start a discussion using the questions below!

  • 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.

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