Placing an egg in salt water will cause the egg to float in this liquid. What causes the egg to float is related to the principle of density. Salt water or sea water is denser than pure water or fresh water.
This experiment is useful for understanding the concept of density. The definition of density is that it is the mass of a substance divided by its volume. If the same egg is put in a glass of pure water, it will sink to the bottom of the glass. This occurs because the egg's density is greater than the pure water's density. The egg's density remains the same whether placed in a pure water or salt water.
What makes the egg float in salt water is the change in the composition of the water with the addition of the salt. The salt water solution is denser than the egg. However, enough salt has to be added to the water for it to have a higher density than the egg.