Look Ma! No hands! (Deshell an Egg with Vinegar)

 I know.  I hate it too.  You try to peel that hard-boiled egg and it takes forever, it's messy, and you lose some of the good stuff with the shell.  Well, try this instead.  It takes a little longer (OK, a lot longer...about 2 days), but it's still pretty neat.

What you need:  2 hard-boiled eggs; 2 short glasses; white vinegar; water.

What to do:  Fill one glass with vinegar and one glass with water.  Leave enough room in each so that you can put one hard-boiled egg in each and no liquid overflows

after 6 hours

(hmmm...what volume of liquid will a boiled egg displace?...perform the experiment is a measuring cup to find out).  Next, wait...for a good long while...come back in 6 hours to check it, and you'll see bubbles forming.  Wait up to 48 hours and you'll see the finished product.  Carefully pour the liquids off from the eggs and rinse the eggs with water.  The shell of the one which soaked in vinegar is completely gone!

What happened?  97% of the eggshell consists of a salt called calcium carbonate.  As you might guess, calcium carbonate does not dissolve in water alone.  If it did, you would never be able to boil the egg in the first place.  However, vinegar is actually a 5% solution of acetic acid in water (you can use your cabbage juice indicators to check the pH).  Calcium carbonate is soluble in an acidic solution. When the shell starts to dissolve, the calcium carbonate is converted into calcium salt, carbon dioxide, and water.  The carbon dioxide creates the bubbles around the egg.  When the shell finally dissolves, the egg floats (it is less dense than the solution).

Basically anyone can do this activity, as long as they have a little patience.  To understand some of the concepts of acids and bases, we recommend this activity for 6th - 8th grade students. Thanks to Nam Tran of U.T. Arlington for contributing this activity.  Nam credits the great lesson he obtained from the "Science Junction" home experiments website hosted by N.C. State University (there are a couple of other activities there, which we will cover later, too).  Tell us what you think.  (You can even eat it afterward...we didn't, but tell us how it tastes)