Answer: Eggshells are made primarily of calcium carbonate. The acid in vinegar softens the calcium of the eggshell. Adding a little vinegar to the water when boiling eggs is an old cook’s trick that makes them easier to peel.
More Info: A child’s science experiment to conduct with eggs and vinegar demonstrates the effect of acidic substances on calcium.
- Place an egg (boiled or raw) in a clear glass or small jar.
- Pour enough white vinegar into the container to completely cover the egg.
- Set the container somewhere that it will not need to be moved for about three days.
- Check the egg daily to observe the changes, but do not remove it from the vinegar.
- After three days, carefully lift the egg from the container with a plastic spoon.
- Try dropping the egg from a height of four or five inches and watch it bounce.
The vinegar has dissolved the outer shell of the egg and thickened the inner membrane. The result is a rubbery, naked egg.
An interesting variation on the egg trick is to soak chicken bones in vinegar for 24 hours. Take them out and tie them into a knot. Leave them out of the vinegar in the open air and they will get hard again. This makes a great show and tell for kids to take to school.
These activities can also be applied to discussions of the effects of acidic drinks on teeth, how acidic water forms limestone caves or the problems brought about by environmental pollution and the resulting acid rain.
“Ask the Van – Illinois Dept. of Physics.” The Physics Van!. N.p., n.d. Web. 14 May 2010. http://van.physics.illinois.edu/qa/listing.php?id=461.
“Is Vinegar Stronger Than Bone?.” TASK. N.p., n.d. Web. 14 May 2010. www.task.uaf.edu/docs/AlaskaDiscoveryLessons/Is%20Vinegar%20Stronger%20than%20Bone.pdf.
“Science of Eggs: Making Naked Eggs Activity.” Exploratorium: the museum of science, art and human perception. N.p., n.d. Web. 14 May 2010. http://www.exploratorium.edu/cooking/eggs/activity-naked.html.