While this science activity might not be accurate in respect to learning about dinosaurs, it is a wonderful experiment to teach young children about polymer materials and scientific principles:
engineering practices - designing a product to fail/fracture at specific points
Procedure: Remove egg from package and submerge in a container of water.
Day 0: The egg sinks to the bottom of the container as it takes on water through the small holes in the shell, releasing air bubbles on the way down.
Day 1: As the dinosaur slowly expands it pushes against the inside of the egg, and the stress causes the eggshell to fail along the preexisting, manufactured crack lines. The dinosaur breaks through the shell after 24 hours.
Day 2: The dinosaur continues to expand. Its entire upper body is visible. Patience wears thin and children manually remove the dino from its shell. :)
The dinosaur is made of a superabsorbent polymer that absorbs a large amount of water relative to its size. As the polymer absorbs water it expands, putting stress on the thin wall of the shell (the shell is also designed to fail at specific points and even seems to break apart somewhat in water). The dinosaur's head "magically" emerges.
This activity tested my children's patience. Each morning during the experiment they would wake up and eagerly view the progress of the dinosaur hatching. They were very excited to find that each of their dinosaurs was a different color and shape. The variety surprised me as well, as I did not realize the dinosaurs were different when I bought them. The dinosaur's texture is rubbery and a little slimy and my kids were a little hesitant to touch their dinos. We changed the water several times during the growing period because it became cloudy from various particulates breaking off the egg and dinosaur.
After we removed the dinos from their eggs we placed them in a bowl of water so they could continue growing for several more days. Later, after we removed the dinosaurs from the water, they slowly shrunk back to a smaller size as the water evaporated. If I were to try out this experiment out again, I would have the kids measure their dinosaur after we removed it from its shell and continue the measurements every 12 hours as the dino grew in the water. I would also have them record how long it takes for the dino to shrink back down and the final, baseline size so that we could calculate the percentage of expansion.
This is my first attempt at participating in Science Sunday. If you enjoyed this post you can find more science experiments involving kids at http://adventuresofmommyness.blogspot.com/search/label/Science%20Sunday and even join in the weekly meme if you like!