Sink or Float
Okay, quick...If you drop a boiled egg into a glass of water, will it sink or float? Now, what if you drop a fresh egg into water? Sink or float? (Both fresh and boiled eggs will...sink!)
So, now have your child pour a few Tablespoons of salt into the water with the fresh egg in it (count the number of Tb). The salt makes the water more dense than the egg...and voila! Floating egg!
Now, how many Tb does it take to make a boiled egg float?
You will need:
Glass bottle with narrow opening just smaller than the boiled egg
match or lighter
Place two birthday candles in the top of a boiled egg. Light the candles and hold the bottle over the candles to heat up the air a little bit. Now place the bottle on top of the candles. The fire will burn out the oxygen from the bottle, creating a lower pressure area and a vacuum will form. Up goes the egg, sucked up into the bottle! (http://kitchenpantryscientist.com/?tag=egg)