Boil enough eggs so each science group in the classroom can have one egg. Give each group a small jar that is big enough to hold the egg while it is covered in liquid. Pour enough vinegar into the jar to cover the entire egg. Leave it in the vinegar for 24 hours, then check it. The shell should be dissolved because eggshells are made of calcium carbonate and vinegar is an acid. This experiment can be done with a raw egg but it may be messier.
Break the small end of four eggs and pour out the liquid. Place clear tape around the center of the eggs and cut them in half with a knife or scissors. Discard the broken end of the eggs. Place the eggshells, open side down, on a table, forming a square with the shells. Demonstrate the amazing strength of the arch shape. Place library books on the eggs and see how many they can hold before they break.
Place a raw egg in a plastic bag and hold it in your hand. Squeeze the egg with even pressure on all sides. The egg will not break. Squeeze the top and bottom of the egg at the same time and you will get the same result. Squeeze the egg on only one side. The egg will break. The shape of the egg keeps it from breaking under even pressure.
Collect extracted teeth from a dentist. Wear rubber or latex gloves while handling the teeth. Thoroughly clean them, then let them dry completely. Brush one side of the teeth with clear nail polish. Place each tooth in a different container. Add a different liquid to each container, including water, sugar water, cola, tea and vinegar. Watch the teeth for a few days and compare the reaction each liquid causes on each tooth. Use this to discuss the effects of good diets and dental care.