This simple experiment in water density shows a little one how an egg will float in salt water but sink in tap water. Fill two separate containers with tap water. Add 6 tbsp. of salt to one container and stir it until the salt is completely dissolved Place one raw egg in each of the containers and observe which one floats and which one sinks. Explain to the child that he can float more easily when swimming in the ocean than in a pool or lake.
This experiment is a simple lesson in air pressure. Peel a hard boiled egg and show the child that it will not fit into a narrow-mouthed jar. Place a votive candle inside the jar and light the candle. Put the egg back on the mouth of the jar. The egg will be pulled into the jar slowly. Explain to the child that when the candle burns inside the jar, it uses up all the air in the jar. The outside air is now greater than the air inside the jar and it pushes the egg into it.
An egg's shell is made up of calcium carbonate and is decomposed by acidic vinegar. This leaves behind only the inner membrane and gives it a rubber-like feel. Place an egg with the shell still on in a glass of white vinegar. Let the egg sit for two days. Remove the egg from the vinegar and gently rinse off the shell. Allow the child to feel the egg's rubbery texture. Let the child try to bounce the egg outside.
Despite their reputation for being so fragile, eggs are very strong. Place an egg in the palm of your child's hand so that his fingers are completely wrapped around it. Have him squeeze it tight. Now have him hold the egg between the thumb and forefinger and squeeze the top and bottom. It will not break. The egg is strongest at the top and the bottom and won't break when you add pressure to both ends. However, it will crack if pressure is put on its sides.