My mom told me that one can check whether an egg is rotten by sinking it in a glass of water. If it floats, then it is rotten.
I didn't find any explanation for this phenomenon. If anyone knows one, please answer.
Buoyancy – Why Do Rotten Eggs Float in Water?
buoyancydensityeveryday-lifefluid-staticsphysical-chemistry
Best Answer
The domestic chicken's egg shell has about 7000 pores that allow the embryo to breathe. When an egg rots the yolk and surrounding materials decompose and they give off gasses which can pass through the shell. This allows mass to leave the interior of the egg resulting in less density for the volume of the egg making it more buoyant.