Rainbow Density Cylinder

This liquid density demonstration will impress and educate children who think of liquids as "all the same." Let young kids play with jars of colored water first, seeing them mix... then show them this. They'll surely be impressed!

Step-by-step tutorial

  • Step 1

    This demonstration can be as simple or involved as you like... my two are pretty familiar with density, so we went all out today! Parents of younger children may want to stick with simple ingredients like water, light corn syrup, and vegetable oil.

    Photo reference of how to complete step 1

  • Step 2


  • Step 3

    We happened to have little plastic cups in our craft cupboard, so we filled them a little over halfway full of our liquids.

    Photo reference of how to complete step 3

  • Step 4

    The kids used food coloring to color the water...

    Photo reference of how to complete step 4

  • Step 5

    ...corn syrup...

    Photo reference of how to complete step 5

  • Step 6

    ...and the rubbing alcohol.

    Photo reference of how to complete step 6

  • Step 7

    Now we were ready to assemble! We added the ingredients according to their density. Density is determined by mass: the structure and elements of the molecules that make up the liquid. So some of the liquids are light (and have less density), and some are heavy. Honey (the densest liquid) went in first. We added the liquids to the center of the glass, not against the edge.

    Photo reference of how to complete step 7

  • Step 8

    Next, we added our corn syrup. We'd colored ours purple, but we should have chosen a different color - one that contrasted nicely with the maple syrup on top of it! Bright green would have been a good one!

    Photo reference of how to complete step 8

  • Step 9

    We continuing layering our liquids. (If your colors mix a little, don't worry! They'll separate again.)Here's the order of how the liquids went in:
    honey
    corn syrup
    maple syrup
    milk
    dish soap
    water
    vegetable oil
    rubbing alcohol
    lamp oil

    Photo reference of how to complete step 9

  • Done!

    Now isn't that interesting! Of course, my children had to do this again with their own ideas...stirring, learning what could be colored and what couldn't, what could be mixed and what couldn't... Have fun experimenting!

    Photo reference of how to complete step 10

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