Rainbow in a Jar: Creating Liquid Layers

About the Activity

You may not know this, but some liquids are more dense than others. Put simply, density is a measure of how closely packed a given material is. In this activity, kids will stack various household liquids on top of each other to create a rainbow in a jar and learn the ins and outs of liquid densities along the way!


Grades: 3 - 12
Topic: Fluid Density, Physics
Estimated Time: 30 minutes


Brought to you by Bayer and University of Missouri Extension

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You’ll have most of these at home already, but a few you may need to get from the grocery store.

Pantry Staples (Makes one jar)

  • 1 jar (preferably with a lid, for the bonus activity)
  • ½ cup of blue dishwashing liquid
  • ½ cup of olive or vegetable oil
  • ½ cup of rubbing alcohol
  • ½ cup of light corn syrup
  • Red, green, and blue food coloring
  • 5 bowls for mixing
  • 5 spoons
  • Measuring cups
  • Paper towel or dish rag (for spills)

Optional Supply:

  • Sauce bottles (to help distribute liquids)
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Activity Steps

Before we get started, let’s talk one more time about density. The definition of density is the mass of a unit of volume of a material substance. Again, it’s simpler to think of it as how crowded it is inside. It might seem like density and weight are the same, but they’re different – weight measures the force of gravity’s pull on an object; the greater the mass of an object, the heavier it’s weight.

Okay, let’s get started!

  1. First, make your purple layer by mixing a half cup of the light corn syrup with 1 drop of blue and 1 drop of red food coloring.Did You Know? A pound of feathers and a pound of gold have the same weight, but very different densities. The tightly packed atoms in the pound of gold make it much more dense and take up much less space than the pound of feathers.


  1. Pour the mixture in the bottom of your jar.
  2. Next, carefully pour the blue dish soap down the side of the jar, going slowly so the colors do not mix.Look at That! The blue layer of dish soap is settling on top of the purple layer of corn syrup! That’s because dish soap is less dense than corn syrup.
  3. Next, mix ½ cup of water in a bowl with 2 drops of green food coloring.
  4. Carefully pour your green water slowly down the side of the jar.
  5. Next, gently pour your ½ cup of oil down the side of the jar.
  6. Now, mix ½ cup of rubbing alcohol with 2 drops of red food coloring.
  7. Carefully pour the red rubbing alcohol down the inside of the jar.Look at That! Now the layer of rubbing alcohol is laying on top of the layer of water – because alcohol is less dense than water.
  8. Being careful not to disturb your liquids. Set your jar down on the table and enjoy your rainbow!


Bonus Fun:
Mix your rainbow liquid layers together and see what happens!

Reflection Questions
Questions to deepen wonder and understanding.

  1. What liquids do you think are even heavier than corn syrup that we could have used at the bottom instead?
  2. What do you think would have happened if we put the rubbing alcohol on the bottom, then added the dish soap?
  3. What do you think would happen if the liquids mixed (see Bonus Fun)?
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Investigate and Explore
Take your new knowledge to the next level.

Just like the liquids in this activity, solid objects have different densities, too. Think about if you held a stick in one hand, or a steel bar the same size as that stick in the other hand – the steel bar would be a little heavier! That’s because wood and steel have different densities, which, as explained above, is the mass of a unit volume of a given substance. Put more simply, it is the relative heaviness of objects of the same size.


This has real-world implications. For instance, in your own home, salad dressings separate between oils and vinegars, which is why they must be shaken before added to a salad – at least, if you want to enjoy the dressing. Greater implications for this can be seen in oil spills. Oil floats on the surface of open water, which helps emergency responders contain and clean up the spill. Those emergency responders will calculate the spread of the oil in and on top of the water by applying knowledge fluid mechanics (the study of how fluids move) and liquid density.

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