First, we put 2 raw eggs in 2 cups of vinegar (1 for each girl). The girls were excited to see that the eggs were immediately covered in thousands of teeny, tiny bubbles.
After a day or so, the shell mostly disintegrated, and we rubbed the rest of it off. The girls loved carefully holding their naked eggs!
We put each egg back into the cups and added water and food coloring. E(2) chose red food coloring and O(5) chose black. Elliott went into a detailed explanation of osmosis, etc., and they seemed to get it to a certain extent.
The girls were interested to see how the eggs grew when they were in the water.
We put the eggs in cooking oil, and there was no change (we should have used corn syrup). Then we drained the oil and left the eggs in the cups. The eggs deflated after we left them in the cups.