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Rainbow in a Jar

based on 31 ratings
Author: TaniaDakka

How many times have you peeked out the window on a rainy day and seen a rainbow (or two)? Rainbows usually only appear after the rain because the sun's rays bounce off the drops remaining in the atmosphere. As they do, they split into all the colors of the rainbow.

This resembles what you see when you shine light through a prism. The glass splits the white light up into its different frequencies.

In both cases, you need two things: a source of light, and a transparent substance like glass or water.

But wouldn’t it be spectacular to hold a rainbow in a jar?

Problem:

How can we use chemicals to make a rainbow in a jar?

Materials:

  • 1 jar
  • 1/2 cup blue dishwashing liquid
  • 1/2 cup olive oil
  • 1/2 cup rubbing alcohol
  • 1/2 cup light corn syrup
  • Food coloring
  • 5 spoons
  • 5 bowls for mixing

Procedure:

  1. Make your purple layer by mixing 1/2 cup of the light corn syrup with 1 drop of blue and 1 drop of red food coloring.
  2. Carefully pour it into the bottom of your jar.
  3. Carefully pour the blue dish soap down the side of the jar.
  4. Mix 1/2 cup of water with 2 drops of green food coloring.
  5. Carefully pour in your green water down the side of the jar.
  6. Gently pour 1/2 cup olive oil down the side of your jar.
  7. Mix 1/2 cup of rubbing alcohol with 2 drops of red food coloring.
  8. Carefully pour the red rubbing alcohol down the inside of your jar.
  9. Being careful not to disturb your liquids, set your jar down on the table and enjoy your rainbow!

Results:

You should have produced a beautifully layered rainbow in a jar with distinct lines that separate each layer of liquid without them mixing.

Why?

So what keeps all these layers all separated from each other? It’s how dense, or heavy, each liquid is. The corn syrup is heaviest, and sits nicely on the bottom. The dishwashing soap is not quite as heavy as the corn syrup, but it’s heavier than the olive oil, and so on.

Layering them from heaviest to lightest from the bottom up ensures that the rainbow maintains its distinct lines. 

What if you had added the layers in the reverse order? Would you still see a rainbow? Try it. What if you changed the colors around but added each liquid in the original order? Go for it. What happens if you mix your rainbow with a spoon? No matter which new experiments you attempt, be sure to record your results to learn even more about density.

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