When analyzing CO2, water, and oil in terms of density, which material is on the top in a recovery cylinder?

In a recovery cylinder, the arrangement of liquids is primarily determined by their respective densities. Oil has a lower density compared to water and CO2, which means it will float on top of both. In the context of the question, oil being the least dense of these substances positions it at the top of a recovery cylinder.

Water, on the other hand, has a higher density than oil but is less dense than CO2 when considering gaseous states. However, in this situation where all three substances are in a liquid form, CO2 would typically be in a supercritical or liquefied state and would have a density that could be situational compared to water, often being denser than liquid oil but not necessarily placed at the top.

Thus, because oil is the least dense substance in this scenario, it accurately sits atop the other materials in a recovery cylinder. This positions oil as the correct answer to the question regarding which material is located at the top.