# Will water in an oil-filled jar sink or float?

If I pour a spoon of oil on a jar full of water no doubt it will float. But if I were to pour a spoon of water on a jar full of oil would it sink? Why or why not?

## 3 Answers

If it's just a spoon of water, the surface tension of the oil might very well keep the water above the oil. Also, the viscosity of the oil might prevent the water from sinking. There is more to the equation than just the density of the liquids.

• this is a physics forum, not philosphy, my sugggestion is to actually try it, then see what happens, then think of a theory to explain your results...no offence intended, it's just that lots of the questions set here are unverifiable by experiment, this one ain't – user74893 Mar 12 '15 at 20:25

I'm fairly sure that any reasonably large amount of water would sink, simply because it's more dense than oil. A small amount may float due to surface tension.

Provided the Oil is non polar, it is simply a question of Specific Gravity. If the specific gravity ( Term we use in the Oil Industry) or density is greater than 1 (one) the water will remain on the surface, if the Specific Gravity is less than 1 (one) the water will sink. If the specific gravity is 1, add some food coloring, some heat, and you have poor mans lava lamp. For reference Crude Oil can vary in SG from "1.5" or greater ( heavy ) to as light as "0.77". Oil Lighter than 0.77 or API Gravity of 50 is usually referred to as condensate.