I know the past two days I did not post a picture of the egg. The main reason was that the egg was not noticeably changing The first two days the egg had the most dramatic, visible changes. But after that, it was kind of hard to notice anything new. But here was the egg this morning.
See. No change, at least nothing that is noticeable.
Today is the day where we take the egg out and examine it! After giving it a good rinse, this is what the egg looked like.
The egg is soft and slightly translucent! The shell is no longer there! It is just the inner membrane of the egg, called a semipermeable membrane. It felt almost like those disposable blue rubber gloves. It was a brilliant feeling!! Not only does it feel cool, it looks cool too! Look at the wondrous egg when I shine a light through it.
You can see the yolk casting a shadow inside the egg! Check this out, you can squeeze the egg just a little.
What happened, then, to our egg? The acetic acid (vinegar) reacted with the calcium carbonate (the shell) dissolving it. What we have left is calcium acetate, water, and carbon dioxide. For those of us (including me) have a hard time visualizing this reaction, Mr. Spangler provides us with the reaction equation.
2 CH3COOH + CaCO3 -> Ca(CH3COO)2 + H2O + CO2
Acetic acid + Calcium carbonate –> Calcium acetate + Water + Carbon dioxide
Remember all of the bubbles that formed around the egg? Those were carbon dioxide bubbles!! Everything becomes so clear, except one thing… didn’t we notice that the egg got bigger? Good news, we weren’t crazy! Mr. Spangler addresses this aspect and it turns out the egg really did get bigger by the process of osmosis! Right now most of you are saying “Huh?”. Let me help you clear it up a bit.
Vinegar is 4% acetic acid and 96% water. The concentration of water in the vinegar was higher than the concentration of water in the egg. So the water passed through the membrane to make the concentrations even. That is osmosis. I remember learning about it in Biology, it is cool science!
After many days of waiting, all mysteries are solved. Before I go I want to show you how fragile this membrane is. After I sealed the egg inside a plastic bag, I went outside. Raising the bag above the ground about a foot high, I dropped it.
Aren’t you glad we have shells to protect our eggs? Me too.
