WEIRDLY COOL EGG
This is a two-step project that develops over six days with little effort.
For Step One you need:
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1 raw egg in its shell
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1 jar with lid that can hold the egg
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Clear vinegar
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Piece of string
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Pen and/or scissors
For Step Two you need:
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The egg as it is after Step One
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The same jar, washed clean
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Spoon
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Toothpick
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Corn syrup
Step One
1. Measure around the center of the egg with the string, using a pen to mark the egg’s circumference on the string, or cutting the string to the exact size.
2. Make sure that the egg is uncracked.
3. Carefully put the egg into the jar and cover it with vinegar. Close the lid.
4. Check on it periodically over the next 72 hours (three days). Things to notice:
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Bubbles of CO2 form on the shell immediately and increase over time. The shell is made of calcium carbonate, also called limestone. It interacts with the vinegar to create carbon dioxide – those bubbles.
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The shell dissolves and bits float on the surface of the vinegar.
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The see-through membrane stays intact. It does not dissolve in the vinegar.
5. Carefully lift the egg out of the vinegar and put it on a small plate covered with a paper towel. Gently wrap the string around it, and you will see the egg has become bigger.
The water in the vinegar has moved into the egg through the tiny holes in the membrane. But the contents of the egg were too big to pass out through those holes. (The selectivity of materials moving through the membrane is called “semi-permeability.”)
6. Throw out the vinegar remaining in the jar, and wash and dry the jar to get ready for Step Two.
Step Two
1. Pour 3 inches of corn syrup into the clean jar.
2. Carefully place the egg into the jar. Close the lid.
3. Check on it periodically over the next 72 hours (three days). Notice how the egg appears to grow smaller and change shape.
4. Carefully lift the egg out of the jar and put it on the small plate again. (Paper towel covering not necessary this time.) Things to notice:
The egg now has a rubbery outer skin with less content inside. Test it by poking it gently with a spoon, or by trying to lift it from the top with a toothpick. Weirdly cool, right?
Why is the egg smaller now? Because the excess water inside the egg has moved out, but the thicker corn syrup cannot move in. (This time the “semi-permeability” works the other way.)
5. When you are finished examining the egg, throw it and the corn syrup away and wash the jar and spoon.
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Special thanks to Janice VanCleave