Are you familiar with the dynamic density bottle experiment? This interesting experiment was invented by Lynn Higgins, and is sold by various science supply companies.1,2 Two immiscible liquids (usually salt water and isopropyl alcohol) and two different types of plastic pieces are contained within a dynamic density bottle. The plastic pieces display curious floating and sinking behavior when the bottle is shaken. Check it out in the video below:
The plastic pieces in the bottle have different densities. This difference, along with the different densities of the two liquids accounts for the differential floating and sinking behavior observed by the plastic pieces. Awhile back, I figured out how to make these bottles using simple household materials. I also figured out how to make the bottle work using LEGO pieces. LEGO pieces display sink-then-float behavior in a shaken density bottle. However, when two LEGO pieces are connected, an air pocket becomes trapped in between the two LEGO bricks. The trapped air confers a lower density to connected LEGO bricks as compared to unassembled LEGO bricks.
My students and I have continued to study the dynamic density bottle in a variety of ways. One thing we have done in particular is to figure out how to get the dynamic density bottle to work using unassembled LEGO blocks alone. In the video below you can see a bottle that works using only unconnected LEGO blocks:
Would you like to learn how we pulled this off? If so, consider joining Grazyna Zreda and me May 25 – 27th during the “Chemistry Instruction for the Next Generation” online conference. During our session, we will be discussing this particular experiment. You can learn how to easily make your own dynamic density bottle. You can also learn how you can get the bottle to work using unconnected LEGO pieces. If you like colored chemistry experiments, you’ll certainly enjoy seeing how the two different liquids in the bottle can be differentially colored. Of course all of these activities will be connected to chemical principles such as intermolecular forces, density, solubility, and emulsions. Along the way, we’ll share several ides for inquiry-type investigations that you and your students can explore. After all, there’s almost always something new to learn about any chemical system.
Consider joining us, and be sure to check out all the other sessions that will be presented at this online conference. I hope to see you virtually during the conference!
Editors Note: The ChemEd X Conference, Chemistry Instruction for the Next Generation is over. However, Tom's JCE article, The Dynamic Density Bottle: A Make-and-Take, Guided Inquiry Activity on Density, has Author's Choice Open Access. This allows readers to view it without a subscription.