What you’ll need for this experiment is a transparent glass or tumbler that’s filled with water, an egg and salt.
First, check if the egg floats in the glass without doing anything to the water, it will not.
Now add some salt to the water and stir it until it dissolves, check if the egg floats now.
If it doesn’t, add some more salt and try again.
Keep adding more salt until the egg floats.
The egg eventually floats because at that point the density of the salt water is greater than the density of the egg.
This phenomenon occurs naturally in the dead sea, where the salt content in the water is so high that even humans float on it because we aren’t as dense as the salt water.
Is it clear now that the density of an object is the factor that accounts for buoyancy, if an object is denser than the liquid, it sinks. If the liquid is denser than the object, it floats.
Tip: If you add more water to the glass the density of the solution will reduce and you can see the egg sink a little lower.
You can also add different amounts of salt in multiple glasses so you have a line of eggs suspended at different levels.
Here’s a neat video from ‘Sick Science!’ that demonstrates this experiment: