Thursday, May 13, 2010

Science Time (success and failure): Eggs-periment Take the Shell off a Raw Egg

There are two parts to this science experiment (I can only recommend the first).

It's very easy:
1. Supplies needed: white vinegar, water, two egg and two containers.
2. Put one egg in each container, cover one with vinegar and one with water. 
3. Label and set the timer for about 3 hours.
4. Check on the eggs the one in the water will look the same, the one in the vinegar has no shell!
The reason: Vinegar is an acid.  The egg shell is calcium carbonate (the same stuff sea shells are made of). The acid breaks apart the molecules of the shell so it dissolves into the vinegar.  The calcium part floats way from the egg into the vinegar and the carbonate releases carbon dioxide. See the bubbles on the egg? That's the carbon dioxide.

At this point you can gently touch the egg, the outside feels soft - that is the membrane of the egg.
5. Now for the failed part of our experiment...I had read if you kept the egg in the vinegar for 7 days it would be rubbery and squishy, even able to bounce and at least we could pick it up. Nope.  After 7 days (about a hundred years for 6 year-olds) we got the egg out again.  The membrane was more firm and felt much less fragile.  Alas, upon attempted to pick it up, the egg burst.  Maybe a good time to talk about the structure of a cell, but the disappointment was great...I'm trying to figure out if refrigerating it was a bad idea and somehow slowed the reaction...any ideas from you scientists out there? Maybe our expectations were too high.
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JRoberts said...

I found your blog through a friend (her roommate was your sister, maybe? or something like that...)

Anyway, I homeschool and we did this for one of our experiments. It was awesome and we did have ours bounce. We kept ours out on the counter (nasty stinky!) and didn't cover it. We also found that it bounced on lino, but not on grass or cement.

Super cool experiment though. :) Glad I was passed your blog link...I will be back.

Joanna said...

Sounds cool - the shell part anyway! To bad about the non-bouncy egg, but I think its better that you didn't try to bounce it and have a nasty messy to clean up!