Polishing Pennies

3 12 2010

Have you ever noticed that new pennies are shiny and old pennies are darker and sometimes even green. When copper is exposed to oxygen it oxidizes creating a darker layer of Copper Oxide on the outside of the penny. I experimented with several liquids to see if they could make the pennies shiny again.

Get several clear cups and dirty pennies. Try to find pennies that are similar in color, so you can compare how the liquids affect the pennies. Put a different liquid in each cup. I used lemon juice, vinegar, water, and dishwasher detergent mixed with water.

Put the pennies into the cups and wait of five minuets. I put two pennies in the liquids, so I could see if they came out the same. You could use more or only one. After the five minuets I took out the pennies and cleaned them off with a paper towel.

Look how shiny the pennies that were in the lemon juice are! Lemon juice has acidic acid which dissolves the copper oxide. Share your results with us in a comment. What liquids did you use?




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