Earlier this year, we made a fall density tower, and we enjoyed it so much that we decided to make a Christmas version! If you’ve never tried this simple science experiment, you really should. It’s like a grown-up version of sink and float, and it’s fascinating for kids in elementary school up through high school.
My oldest son did a density tower as part of his high school chemistry curriculum, so you never really outgrow this cool experiment.
What is a density tower?
A density tower is a column of liquids that don’t mix with each under, but instead stack up in layers. Density is the amount of matter a certain substance has per unit of volume. Liquids that are less dense will naturally sit on top of a liquid that is more dense.
Oil and water are easy to layer as they WON’T combine because of water’s polarity. The oil will always rise to the top because it’s less dense. However, some of these other liquids can be stirred together and combined. For that reason, you’ll need to be careful as you pour so that the substances don’t mix. It’s not terribly difficult, though, and the results are so worth it!
- A clear glass or jar
- Corn syrup
- Rubbing alcohol
- Food coloring
- Vegetable oil
- Solids items to test
Collect some Christmas items that you can test to see where they land in the density tower. We used a jingle bell, a mini candy cane, a soft peppermint, a pom pom ball, a plastic button, a real cranberry, and some plastic snowflake table scatter. These items worked very well since they landed in a variety of places!
How to Make a Density Tower:
Start by pouring your liquids into the glass.
Pour the corn syrup into the glass first. Make sure that you pour it into the center of the glass or jar, with no corn syrup getting on the sides of the glass. I didn’t measure! I just poured in a nice layer, keeping in mind that I wanted to fit 4 layers in this glass.
Then add water mixed with food coloring. The food coloring will make this layer stand out from the corn syrup. Pour very slowly and carefully.
NOTE: We tried adding a layer of whole milk above the corn syrup, but then when I added the water layer, it mixed with the milk immediately. Steve Spangler Science recommends using a turkey baster, and I think that would have helped! We don’t own one, but we probably should.
Next is vegetable oil. If you pour slowly, the oil won’t have any trouble rising above the water.
I poured the alcohol onto a spoon to slow it down.
I added food coloring to the rubbing alcohol as well. Keep in mind that alcohol does not dissolve the food coloring very well. Gel food coloring doesn’t work at all! I used liquid colors, and I had to do a lot of stirring and wait several minutes to get the color to mix.
Once your liquid layers are complete, it’s time to drop in some solid items!
Drop each item in gently and carefully, and then watch what happens. Does it drop all the way to the bottom? Or float at the top? Or stay suspended in one of the lower layers?
The jingle bell fell quickly through the first three layers, and then it sank slowly through the corn syrup. This is because the corn syrup is more dense.
We knew that the softer mint was less dense than the candy cane, so it made sense that they landed in different places! The pom pom ball surprised us by sinking to the bottom of the alcohol layer.
The plastic button made it all the way through the top three layers and then stopped at the boundary with the corn syrup.
This little plastic snowflake table scatter surprised us the most! We expected it to float on the top, but instead it sank down to the top of the water layer. In other words, it floats in water, but not in alcohol or vegetable oil. So cool!
Have fun making a Christmas density tower!
Need more Christmas science activities? We’ve got lots of cool science and STEM activities to keep kids busy all season long.
Print these Christmas Tree Tessellations. Kids can decorate the trees and then assemble them into a really cool tessellation picture!