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| An egg floats after its shell dissolves |
This activity complements my website's Ocean Acidification Kids' Page. Ocean acidification is happening because about a third of the carbon dioxide released from the burning of fossil fuels ends up in the ocean, where it reacts with ocean water, causing the water to grow more acidic.
The creatures most likely to be affected by ocean acidification are corals, shellfish, and some types of plankton that have shells or skeletons made of calcium carbonate. This is because acid is corrosive to calcium carbonate.
Bird eggshells are also made from calcium carbonate. In the following experiment you will see what happens when you put an egg in vinegar.
Ages 7 and up; click here for PDF
You will need:
egg
cup or jar
bowl
white vinegar
knife
Preparation
Place the egg in a cup, and cover with vinegar overnight.
Observation
Look at the egg. Do you notice anything unusual about it? For one thing, it now floats. For another, it is probably covered with tiny bubbles. Carefully pick it up and place it in a bowl. The egg’s surface feels soft because the calcium carbonate shell has dissolved, and all that is left is an opaque white membrane. The egg looks and feels hard boiled, but if you puncture the membrane, you'll see that it is raw.
Look at the egg. Do you notice anything unusual about it? For one thing, it now floats. For another, it is probably covered with tiny bubbles. Carefully pick it up and place it in a bowl. The egg’s surface feels soft because the calcium carbonate shell has dissolved, and all that is left is an opaque white membrane. The egg looks and feels hard boiled, but if you puncture the membrane, you'll see that it is raw.
What’s Happening?
Bird eggshells are made from calcium carbonate. Acid is corrosive to calcium carbonate, so vinegar dissolves the shell. All that is left is the membrane that lines the inside of the shell. Since the egg isn’t as dense without its shell, it now floats. Air bubbles form when the dissolved carbonate from the shell reacts to form carbon dioxide gas.
More to Try
Like eggshells, seashells are made from calcium carbonate. Try putting a seashell in vinegar and see what happens. Don’t do this with a seashell you like, however, because chances are it won’t look the same when you are done!
Bird eggshells are made from calcium carbonate. Acid is corrosive to calcium carbonate, so vinegar dissolves the shell. All that is left is the membrane that lines the inside of the shell. Since the egg isn’t as dense without its shell, it now floats. Air bubbles form when the dissolved carbonate from the shell reacts to form carbon dioxide gas.
More to Try
Like eggshells, seashells are made from calcium carbonate. Try putting a seashell in vinegar and see what happens. Don’t do this with a seashell you like, however, because chances are it won’t look the same when you are done!
Very nice...
ReplyDeleteIts really very interesting. You blog is full of interesting stuff for all of us...
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