This lesson developed by Michelle M.
Recommended Age: Preschool and Early Elementary
Can I make an egg float?
When you added salt to the one glass of water, you made this water heavier. A heavier liquid will support objects with more weight than a lighter liquid will. The salty water actually weighs more than the plain water.
When you put the egg in the salty water, it is able to float. The same thing happens when we swim in sea water or, especially, in the very salty water of the Great Salt Lake in Utah or the Dead Sea in the Middle East. When we are in salty water, we float more easily or feel more "buoyant."
You can do this experiment with friends like a magic trick! (If your egg won't float, you may need to add some more salt, so try this trick out ahead of time!) Have both glasses ready, one with the salt in it. Tell them that you are magically going to make one of the eggs rise and float! Pass the eggs around so everyone can see they are real eggs. Let them look at the glasses of water. The salt will be dissolved so they can't tell that there is anything but water in the glasses. Be sure you know which glass has the salt in it!
Drop one egg in the plain glass of water and predict it will sink. When it does, say something dramatic like "Ta-dah!"Next, you want to act like a magician and pretend that YOU are making things happen. Move your hands over the glass of salty water as if you are casting a spell over it. Drop the other egg into the water while predicting it will to rise and float. The egg sinks! Now you will want to say some "magic words." You might try "Voilà!" (a French word that sounds like "vwah-lah" and is used like "ta-dah"). The egg will rise and float!