Water is less dense than honey. Rubbing alcohol is less dense than water. Poured carefully on top of each other, from heaviest to lightest, they can create distinct layers. Add more liquids of different densities, such as baby oil, milk, dish soap, as well as a bit of food coloring, and you’ve got an impressive Density Tower.
We’ve seen plenty of three, five, and seven layer density towers on the internet, but this Amazing 9 Layer Density Tower from Sick Science! might be the most impressive. Bonus: Experimenting with a bolt, grapes, a cherry tomato, a ping pong ball, and more.
Whether an object sinks or floats depends on its density compared with the density of the liquid into which it is dropped. All types of matter—solids as well as liquids—are made up of many different atoms. Depending on the mass of these atoms, their size and the way they are arranged, different substances will have different densities. The density is characteristic for each individual compound and defined as the mass of a compound divided by its volume. In other words, the more matter there is in a certain amount of volume, the denser a substance is. One cubic centimeter of rock, for example, is much heavier than a cubic centimeter of wood. This is because there is much more matter in the same volume of rock compared with the wood.
Liquids can also have different densities. Freshwater, for example, has a density of about one gram per cubic centimeter at room temperature. Any compound—liquid or solid—that has a higher density than water will sink whereas substances with a lower density than that will float.
Watch and try the experiments in these videos next: Surface tension and The Cheerios Effect, Pattern distortions seen through a glass of water, Homemade Lava Lamp, and Hot & Cold Water Science Experiment.