Here is a chemical reaction that is easy and fun to do – cleaning pennies with vinegar and salt! All you need are some dull, dirty pennies, salt, and vinegar. We put our pennies on a paper plate to work with them.

I asked the boys to try cleaning their pennies with soap and water first. They scrubbed, but were not able to get the pennies any cleaner! I explained that pennies get their dull color when the copper in them reacts with oxygen in the air to form copper oxide. Sometimes, pennies even get a greenish hue from the copper oxide.

Since the copper oxidizing is a chemical change and not a physical change (like simply getting dirt on something), soap will not wash it off. It takes a chemical reaction! The acetic acid in the vinegar reacts with the copper oxide and dissolves it.

We sprinkled salt over the pennies, and then used a dropper to coat them with vinegar. We rubbed the pennies a little with the salt, and they were shiny again!

You can also dissolve the salt in the vinegar and then dip the pennies in the solution. I’m not sure if there is a benefit to using either method.

The boys were impressed with the results!


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  1. Pamalot Jun 16, 2011

    thank you for this idea. In our kindergarten class we have been exploring $$ and had fun washing pennies!

  2. Sally Sep 17, 2012

    I spent over an hour exploring your fun blog last night, which is something I don't usually do! You not only have wonderful ideas, but such a good way with your kids, especially teaching them gospel and Bible truths. We homeschool our 3 boys in Hawaii, and are always looking for more great ideas. You blog is definitely a keeper! Mahalo nui loa

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  6. Jill Oct 20, 2020

    If you are planning on selling them do NOT use this. It ruins them. I tried it and lost a good bit of money...beware


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