GRAND RAPIDS, Mich. — When we stopped by Plainfield Child Care in Grand Rapids, we discovered some very young kids that we were eager to learn. That said, we had to keep things simple for the age group. This experiment deals with density (how heavy something is) and the effects are demonstrated using eggs. You'll also need two glasses, water, and table salt, as well as two eggs.
In short, when one glass is filled with normal, everyday tap water, and an uncooked egg is dropped in, it sinks. The egg is heavier than the water that surrounds it, so it sinks to the bottom. The egg is more dense. There are more molecules per square inch.
When the second glass is filled with the same tap water, we changed the game/dynamics by adding three tablespoons of Morton table salt. Why does that matter? Well, the water becomes more dense than the egg itself. That means the eggs float since the water almost weighs more. By increasing the density of the water and adding salt, and essentially adding more molecules per square inch, the egg simply floats.
Perhaps density can be described this way too. I remember my dad always told the joke "Which weighs more, a pound of feathers or a pound of lead?" Most say the lead of course, but the fact remains they both weigh the same because it's a pound. Now, if we said which one is more dense, it would be the metal/lead.
Air has density too. Cold, dry air is more dense than warmer, moisture-filled air. Therefore, it wants to sink. The warmer air rises because it's less dense. This of course has huge weather ramifications since rising air means cloud formation and perhaps precipitation. Think about freezing temperatures and frost setting into our fruit crops in September or October. That cold, dense air sinks to the ground and can damage crops. Farmers can turn on huge fans to rotate the warmer air aloft and "stir up" the atmosphere in an effort to save their crops.
So next time you need a way to show density to kids, try the egg experiment.