Why do eggs float in salt water and sink in fresh water?
The density of the salt water is greater than the density of the egg. Items sink if their own density is greater than the density of whatever they are trying to float in. Items float to the top if their density is less than the density of what they are floating in, and items hang in the middle if the densities are the same. Adding in the salt gives the water a greater density than the water did had before, so the egg doesn’t float in freshwater.