Jessica floats an egg in water
Jessica is 6 years old and today she invited me over to show Nanogirl an experiment changing the density of water.
First she filled a glass with water and placed an egg in it, then she poured 10 tablespoons of salt into the glass and stirred it to dissolve the salt.
She then put the egg back in the glass and it floated!
The science behind this is that adding salt changes the density of water. Because saltwater is denser than normal water, the egg ends up floating instead of sinking.
Density is the amount of matter contained in a given space or volume. When there's more amount of matter (such as salt) in a given space or volume, the object is considered denser and at the same time heavier.
In our experiment the egg is denser than normal water and so it is considered heavier and sinks. If we add enough salt, the egg floats because the liquid has more density.
This is also the reason why you float more if you swim in the sea compared to a swimming pool.