It is a well known fact that oil floats on water. In many situations we see this phenomenon such as after rainstorms when it is common to see oil on top of puddles. It is also common to see oil droplets on top of the water when washing dishes. Many experiments are undertaken in elementary school to observe this fact of science. So why does oil float on water? Read this article to find out.
What causes oil to float on water?
There are two reasons why oil floats on water. The first reason is that oil is less dense than water. This means that it is lighter and is able to float to the surface of water. Having less density makes the oil float on the water just like a straw or a piece of foam. Although some oils are denser than water, the majority of oils are lighter. The density of pure water is calculated at 1000kg/m3. This means that a cubic meter of water weights one metric tonne. Oil, on the other hand, is less dense than water and has a density of approximately 800kg/m3. This means that a cubic meter of oil is equal to 800kg, compared with a cubic meter of water at 1000kg. So just like a helium balloon will rise in the air because it has less density, oil will rise in water and float on the top.
Density isn’t the only reason that oil floats on water. The other reason is the fact that oil is hydrophobic (scared of water). Oil molecules do not dissolve in water due to this characteristic. They will instead bond together and float to the surface. A lot of oil will create a film on the top of the water. Oil is non-polar and water is polar so they repel each other and this causes the oil to float.