Strong Eggs!
Here's an activity that my kids loved. It demonstrates how eggs are very strong yet thin enough for the chick (or other bird) to emerge. If you've read my posts on the now-quite-forgotten evolution vs. creation thread, you know that I am a creationist and this is one activity I use to show evidence of a creator by showing how the egg is just the perfect thickness and shape for what it has to do. So, if you have the liberty (ie. at Christian school) to add in "aren't they created well?" all the better.
However, without a philosophical bent, the activity is still a blast. Your comment will probably be, "Wow, they are strong, yet the chick can still get out."
Anyway, get three raw eggs (from the grocery store, these aren't for hatching!) and six plastic bottle caps like you find on bottled water or pop bottles. Also get some paper towels and some cleaner (even hand soap and water is okay) because this is slightly messy.
Arrange three of the bottle caps upside down (so that they look like little cups) on a table in a triangle about 6" or so apart. Put one egg in each cap, the tall way (so it's as tall and narrow as can be, not the short and wide way!). Then put a bottle cap right side up on each egg. The bottle caps don't add any strength, all they do is provide a transition between the flat table and the round eggs (or the round eggs and the books).
Now, the fun part, start stacking big hardcovered books on these three eggs. We always weigh the books as we add them. The last time we did this, we got 72.5 pounds of books stacked on these three eggs before they broke.
Then you can have a fun discussion about the shape of eggs and about birds hatching, etc.
You can also shine a light through a raw egg.
You can also spin both a raw egg and a hard boiled egg. The raw one wobbles and the hard boiled spins evenly. This is due to the sloshing in the raw one!
Another cool thing you can do is put two raw eggs (one fresh and one pretty old -- save one in the frig for a few months if you have time) in a pan of water. The old one, which has lost some of its mass to evaporation (the shells are actually a tad porous) floats while the fresh one is still dense and it floats.
You can also float a raw egg in water. Start by putting the egg in a tall glass of tap water. It should sink. Slowly add lots of salt to the glass (remove the egg so you can stir the water easily) and you'll be able to float the egg because salt water is denser than fresh water.
There's also science (is it long chain polymers??? It's been such a long time) in beaten egg whites (like making a meringue). You might want to do a websearch on this and then beat some whites and discuss why they are different than the unbeaten whites and why you can go from slimy unbeaten whites to foamy beaten whites but you can't go back. Once they are beaten, they stay that way. I honestly forget the science behind it but it's interesting.
A friend of mine just taught her kids about Faberge and the eggs he made. Then, she provided them with wooden eggs from the craft store and paint and sequins and ribbons. They really made some beautiful eggs! This is a great art activity for all ages (and all faiths, since it's an artist study).
Alicia