activity 8: Corrosive Cola Make all your pennies sparkle with a can of cola. It makes you think about what it's doing to your teeth! You will need: 1 can of cola A clean glass jar Some dirty 1 pence pieces A sieve Kitchen towel What to do: Pour the can of cola into the glass jar. Drop the dirty pennies into the cola. Leave for 30 minutes to an hour or until the pennies appear shiny. Whilst holding the sieve over the sink, empty the cola and pennies into it. Rinse them with water then dry them off with a kitchen towel. What is Happening! Old pennies become darker because the copper in the pennies combines with oxygen from the air forming copper oxide on the surface. When pennies have a coating of copper oxide they look dull and dirty. Cola is acidic as it contains phosphoric acid, carbonic acid and citric acid - these acids dissolve the copper oxide revealing the untouched metal beneath.
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