Why do these liquids stack so cleanly? For the same reason that helium floats on air, and air floats on water: it’s all about density. Density, or mass per volume, measures how much stuff is squeezed into a given space. The higher the mass-to-volume ratio, the denser the object. A ten-gallon bucket of rocks occupies the same amount of space as a ten-gallon bucket full of air, but it contains more mass– it’s more dense. Unsurprisingly, the bucket of rocks also feels heavier. Mass and weight are closely related! Denser substances are heavier by volume, so they sink beneath less dense substances. We can layer household substances of different densities to get a crazy stack of liquids!
The corn syrup is the most dense of our layers because there’s more “stuff” squeezed into a cubic inch of corn syrup than a cubic inch of maple syrup, whole milk, or any of the other density column ingredients. Weigh a fluid ounce of each liquid and you’ll find that corn syrup is the heaviest. It makes sense that it should sit at the bottom of the stack!
Trying this at home? For best results, pour slowly, and avoid letting the liquids run down the sides of the container. Adding your liquids in order from densest to least dense will also help to keep the layers cleanly separated.
For more info on density and buoyancy, check out our Coke vs Diet Coke experiment here!