Liquids have density, too. You can perform several experiments with different types of liquids to determine which is more dense. These experiments can make a good science fair project; use them as a foundation and then come up with your own ideas of what to test.
image/text credit: DaveHax
Simple density science experiment that you can try at home to see how liquids and objects with different densities behave. Using three fluids (syrup, water and oil) we can see they clearly have different densities, and form clear layers. By dropping items with different densities into the glass, we can see which fluids are denser than them.
The science secret here is density. Density is a measure of how much mass is contained in a given unit volume (density = mass divided by volume). If mass is a measure of how much “stuff” there is in an object or liquid, density is a measure of how tightly that “stuff” is packed together.
Based on this density equation (Density = Mass ÷ Volume), if the weight (or mass) of something increases but the volume stays the same, the density has to go up. Likewise, if the mass decreases but the volume stays the same, the density has to go down.