Here’s another super cool fall science experiment to try! Make a density tower (also called a density jar) with a fun fall twist.
Kids (and teens) will be amazed at how the different liquids sit on top of each other without mixing. It’s also fun and kind of mind-blowing to drop in solid objects and see where they position themselves in the tower.
We did this experiment as part of our science curriculum, and then modified it a bit to make it fun for fall. Such a big hit!
What is a density tower?
Density refers to the amount of matter in a given volume. If a substance has a greater amount of mass per cubic centimeter (cm3) than another substance, then its density is higher. For example, a rock has a much higher density than a sponge or a pillow.
A density tower (or density jar) is a “stack” of liquids that are layered in a jar. Because each liquid has a different density, the liquids can be made to layer on top of each other without mixing.
Objects will float if they are less dense than the liquid they are in, but they will sink if their density is greater than the liquid.
We chose to use 4 liquids for our density tower. I have seen density towers with 8 – 9 different liquids, but I felt like 4 liquids made an impressive density tower without requiring us to purchase a lot of things.
Supplies Needed for a Fall Density Tower:
- Tall clear glass or jar
- Corn syrup
- Food coloring – 2 colors, we used green and orange
- Vegetable oil
- Rubbing alcohol
- Candy pumpkins and candy corn
- Small paper clip
- Small stone
- Anything else you want to put in there!
These are the solid items that we added to our density tower. Use whatever you have on hand, although the fall candies might be worth purchasing.
Other ideas: raisin, fall leaf, conker (for my UK friends!), twig
How to Make a Density Tower
Start by pouring your liquids into your glass or jar. Pour slowly, and tilt the glass so that you can pour the liquids on the side of the glass.
Pour the liquids in this order: corn syrup, colored water, vegetable oil, rubbing alcohol.
I mixed a few drops of food coloring with the water and the alcohol in separate containers before pouring them into the density tower. It takes the food coloring a few minutes to dissolve in the alcohol. You’ll need to do some stirring, and even then, some of the food coloring will probably remain on the bottom.
Then start adding solid items to your density tower. Drop the items in gently.
We thought it was interesting where the objects positioned themselves!
The penny and the rock went right to the bottom, which was not surprising since we knew they were very dense. The paperclip did end up at the bottom of the glass, but it dropped quickly through the water and then fell very slowly through the corn syrup. A piece of candy corn stopped at the boundary between the water and the corn syrup, but the candy pumpkin slowly fell all the way to the bottom of the glass.
The acorn surprised us by floating near the top of the oil level.
Then the cork floated about half-submerged in the rubbing alcohol.
Such a cool science experiment!
Need more Fall STEM and Science Ideas? We’ve got lots!
You’ll definitely want to check out our Candy Pumpkin Rube Goldberg STEM Challenge! This is SO much fun, and works well for kids of all ages (including middle schoolers).
Then we also have a whole collection of all the Best Fall STEM Activities. Leaf activities, pumpkin science, candy corn catapults, and more.
Lindsey Sep 22, 2022
I am an ardent follower of yours and use your ideas for my after school STEM club in the UK. As far as I know we don’t have corn syrup here and does rubbing alcohol have another name too as I am unsure what we might call that here too.
Thanks so much
Sarah Sep 24, 2022
It looks like the closest thing to corn syrup would be golden syrup. It's made with cane sugar, so it won't be exactly the same. You're just looking for a thick, viscous liquid so that it will stay on the bottom of the jar. Rubbing alcohol might be called surgical spirit or isopropyl alcohol. I hope that helps!
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