Place a few eggs in a container so the eggs aren't touching. Slowly pour white vinegar into the container until the eggs are completely submerged. Bubbles should form on the eggs. Cover the container and store it in a refrigerator for 24 hours. After 24 hours, the shells of the eggs will have dissolved enough so they appear mostly transparent. The eggs' membranes will still be intact, which keeps the eggs firm in their shapes. The transparent shells will allow the inside of the eggs to be visible. Carefully remove the eggs from the container and discard the white vinegar solution. Put the eggs back in the container and fill the container with fresh white vinegar. Cover the container and store it in the refrigerator for another 24 hours. This time, after 24 hours, the eggs will be completely translucent and the membrane will flex when squeezed. The eggs are still breakable and can cause a mess, so have paper towels ready.
Fill one cup with hot water and another cup with cold water. Place 3 sugar cubes into the hot water and have the kids stir until the cubes dissolve. Time it to see how long it takes. Put 3 sugar cubes into the cold water and stir. Have the kids tell you which took longer to dissolve. The hot water should dissolve the cubes faster because moving molecules are spread further apart, which allows more sugar molecules to fit in between.
You'll want a safe area to perform the diet soda geyser; this experiment can get pretty explosive. Drop a Mentos candy into a 2-liter bottle of diet cola and watch the soda rocket out of the bottle. The gelatin and gum arabic from the dissolving candy disrupts the water mesh, and the expanding bubbles come shooting out of the top. You can also roll up a piece of paper and insert it in the top of the soda, which allows you to drop in more Mentos. This will create a higher geyser.
Place a sauce pan over medium heat and stir together sugar, corn syrup, water and cream of tartar with a wooden spoon until the sugar crystals dissolve. Use a pastry brush soaked in warm water to help any sugar crystals on the side dissolve. When the mixture reaches 300 degrees, remove it from the heat and let it cool just a bit. Add flavor, color and citric acid. Stir the mixture. Quickly pour into molds or tiny pools on an oiled cookie sheet. Have the kids insert a lollipop stick into each one. Let it cool for 10 minutes until they are hard and have the kids wrap them in cellophane. Store in a cool, dry place until they are ready to eat.