Try this cool floating eggs experiment to study density. First, make a saturated solution of salt and warm water. We added blue food coloring for fun too. When the salt is dissolved, put an egg in it. You’ll see the egg rise to the very top because the egg is less dense than salt water. (That’s the middle glass in the picture.)
Next, add blue food coloring to a glass of plain water and drop the egg in. You’ll see the egg sink to the bottom! What happened this time? Well, the egg is more dense than plain water, so it sinks.
Finally, try a cool trick. Make the egg float in the middle of the water. Put warm salt water on the bottom (about 2/3 full). Then slowly and carefully pour in plain water on top. Gently put the egg in and watch it float between the 2 layers–above the salt water and below the plain water.
The explanation behind this experiment is simple – DENSITY! The egg placed in salt water floated and the one in tap water didn’t; that’s because salt water is denser than fresh water.
Density refers to the amount of matter contained in a given space or volume. When there’s more amount of matter in a given space or volume, the object is denser. When salt is dissolved in water, it breaks down into ions that are attracted to the water molecules. This attraction causes them to bind tightly, increasing the amount of matter per volume (density). Instead of just having hydrogen and oxygen molecules in the water, sodium and chlorine joins in too(salt or NaCl). Salt water now has more particles in it compared to the plain tap water we started with; in other words, it’s more dense.
Density is pretty cool, huh?