Kids’ Science: Rainbow Jar

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Kids’ Science: Rainbow Jar

Activity for ages 2 and up.

We’ve had kids’ science fever on Playdough to Plato these last few weeks. We mixed up some magic rainbow milk and shared some of our favorite preschool science experiments from across the web. This rainbow-themed science activity for kids has been one of the most popular in the bunch.  Kids and grown ups agree – Rainbow Jar is a fun, colorful way to teach kids about density.

 

To Prep

 

This project requires quite a few things but most of it is probably stuff you already have lying around your house.  You’ll need:

  • 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,
  • and a dropper {which I forgot to photograph}.

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

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

 

To Play

 

C was really excited when I told him we were going to make a rainbow in a jar. His exact words were actually, “What?! How can you have a rainbow in a jar?”

 

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.

DSCN0594

I had C 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.

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.}

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

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

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

The dish soap came next.  {Once more — pour it in the middle!}

Rainbow Jar 4

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

Rainbow Jar 2

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.

Rainbow Jar 2

Our rainbow was done!  We held it up carefully to the light, making sure not to shake it, and admired our beautiful creation.




Find More

 

For more science fun with kids, walk on eggs, make rainbow milk and whip up a batch of fizzy bath bombs.

 

Pin It!

Fun kids' science experiment. Make a rainbow in a jar. {Playdough to Plato}

About 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.

7 Comments

  1. Can’t wait to try it.

  2. So fun! I did this with a group of 3rd graders today, and they thought it was amazing! Thanx for the great idea!!

  3. Going to do this tomorrow with my three year olds.

  4. Thank you for a great idea! I’m looking forward to do this with the children in the preschool where I work. I live in Sweden and corn syrup isn’t something we have here. Is there anything I can replace it with, or is it an option to just skip it? Is it like any other syrup?
    Thank you for your answer!

  5. I am happy to read that the rainbow jar is helpful, Jenny!

    You could skip the corn syrup. You will lose a layer but it will not be too noticeable.

    Fingers crossed that your preschoolers love the activity too!

  6. Has anyone shook up the bottle? what happened? did the layers separate again? I know that my pre-kg kids will shake up the bottle, so I just want to be prepared!

  7. Lovely! As a chemistry teacher though I cringed a bit at the explanation. I know you’re trying to simplify for kids, but it will make it more confusing when they’re older. Instead of more marbles, put the same number of, say, marbles and packing peanuts in two cups. They take up about the same amount of space, and have around the same number of pieces (molecules) but one is heavier than the other because there are either more small particles or heavier small particles (atoms for your reference) in each bit of space. Or you can compare balled up paper to stacked paper. Put as much of each as you can in a shoebox (same volume) and the stacked paper box will be heavier. More ‘stuff’ (matter) can fit into the same space so that shoebox (unit of volume) is heavier.

    There are NOT necessarily more molecules in denser liquids in the same amount of space… There could be more, there could be fewer. There IS more matter in that bit of space than for the less dense liquid. (I keep emphasising ‘same bit of space’ because you can’t compare the weight of one cup of water to one drop of oil- density is mass per unit volume. It’s like that brainteaser, what weighs more, a ton of feathers or a ton of bricks? They both weigh the same! But the bricks will take up much less space because they’re more dense. Or to flip it, if you have identical boxes filled with bricks vs feathers the box of feathers will be lighter because they’re less dense. See why volume is important?)

    I know this may sound pedantic, but it really does make a difference later. And my students always complain that every year they need to unlearn the ‘lies’ they were taught before (their words not mine!)

    Thanks for hearing me out!

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