Rainbow Jar

Science for kids ages 2 and up.

We love fun kids’ science and this easy activity is one of our favorites. With just a few household ingredients, you can actually pour a rainbow in a jar. Cool, huh?!

P.S. Looking for some easy ways to add super cool, hands-on science to your classroom or home? Hop over and grab our super cool science kit!

Science for kids, kids science, rainbow jar, make a rainbow in a jar

Getting Ready

This project requires quite a few things but most of it is probably stuff you already have lying around your house.  To get ready for the science activity, I grabbed my supplies.

St. Patrick's Day Science Experiment for Kids: Rainbow Jar.

  • A tall, see-through container {I used a clean mason jar}
  • Honey
  • Light corn syrup
  • Dish soap {either blue like Dawn or green like Palmolive}
  • Olive oil,
  • Rubbing alcohol
  • Water
  • Food coloring
  • A dropper

I also grabbed two identical containers and some marbles so that I could give my son, C, a brief explanation about density.

The Science Behind It

As always, my son was really excited when I told him we were going to do a little kids’ science. I introduced density by explaining that different liquids have different weights.

“Everything is made up of teeny tiny things called molecules,” I said.  “Some of these liquids have a lot of molecules in them and some of them have only a few.” I showed him two containers that were the same size.  One had a bunch of marbles in it, one only had six.

Science for Kids Rainbow Jar

I had my son hold the two containers and asked him which one was heavier.  “The one with more marbles,” he said.   I explained that it was the same with our liquids — the ones with more “marbles” {molecules} were heavier and would stay at the bottom of the jar.

St. Patrick's Day Science Experiment for Kids: Rainbow Jar.

Pour a Rainbow in a Jar

Now it was time to make our rainbow!!  First we poured in the honey.  Be sure to pour it into the middle of your container — don’t let it touch the sides.

Next he poured in the corn syrup. {We’d colored it purple using the food coloring.} Again,  pour it into the middle of the container, not touching the sides.

Then we added the dish soap.

Make a Rainbow in a Jar

We poured in regular water that we colored blue. {If you’re using blue dish soap, obviously color your water something different. Again, in the middle, in the middle!}

The olive oil went in next. Do you know what I’m going to say? That’s right, pour it in the middle. Also, I recommend pouring a fairly thick layer of oil — it will come in handy for the next step.   Last but not least was the rubbing alcohol.  We colored it red — that in itself is a cool peek at different densities because the food coloring just sits at the bottom of the alcohol when you first drop it in.

Rainbow Jar 3

BUT WAIT! DON’T POUR IT IN THE MIDDLE!   This is where the dropper comes in.  If you pour the alcohol straight in, it’ll probably pick up the blue food coloring you used in the water and your rainbow will be ruined.  We found the best way to add it was dropping the alcohol along the side of the container using a dropper.  The key was  not “breaking through” the oil layer into the blue water layer beneath it — that’s why I suggested putting a thick layer of oil.

How to Make a Rainbow in a Jar

Our rainbow was done!  We held it up carefully to the light, making sure not to shake it, and admired our beautiful creation. Fun kids' science experiment. Make a rainbow in a jar. {Playdough to Plato}

Find More

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Jen Rice

Jen is a mom of two {ages 5 and 1} who loves cross stitching, surfing Pinterest and finding fun and creative ways to get her kids learning.

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  1. Are there any standards for elementary school grades that would go with the activity? I am actually using this activity for my science course I am taking this summer and am making a lesson plan based on it.

  2. After making the rainbow jar, for how long can you keep it?
    My guess is that there are fairly stable at room temp, but I’m not sure.

  3. janelledawn says:

    would you have another suggestion to use in place of the corn syrup?


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