Dye eggs with onion skins to teach preschoolers that vegetable skins contain natural dyes. Boil water in a large pot. Wrap hard-boiled eggs in the skins of red onions and secure the skins with a rubber band. Add the eggs to the pot and boil for about 15 minutes. Remove the eggs and allow them to cool. Remove the skins to reveal that the eggs have been dyed a red-purple color.
Perform an experiment which demonstrates that an egg will float when salt is mixed into a volume of water. The dissolved salt increases the density of the water, making the density greater than that of the egg, causing the egg to float. Ask preschoolers what might happen if you drop the egg in the water. Ask preschoolers if they believe the egg will sink or float. Drop a hard-boiled egg into water. Remove the egg and then add salt to the water. Drop the egg in the water. Discuss why the egg floats when salt has been added to the water.
Allow preschoolers to observe an egg as it hatches. Purchase an incubator and a chicken egg designed for hatching. Turn the incubator on 24 hours before putting the eggs in the incubator in order to regulate the temperature to 99 degrees Fahrenheit. Turn the egg three times per day. Mark an "O" on one side of the egg and then an "X" on the other side to keep track of your rotations. Stop turning the egg on Day 18 to allow the chicks to reorient themselves and hatch upward. The chickens will hatch after about 21 days.
Collect the shells from hard-boiled or raw eggs. Clean the eggshells and dry them with a towel. Color the eggshells with drops of food coloring. Allow the eggshells to dry. Put the eggshells into a plastic bag and show preschoolers how to crush the eggshells with a rolling pin or light mallet. Provide each child with a piece of construction paper or card stock cut into the shape of an egg. Encourage children to glue eggshells onto the egg shape to create a collage of eggshells.