Saturday, February 18, 2012

President's Day Science

President's Day is coming up and we thought we would honor the day with a little science experiment. This activity used to occupy me for many an afternoon when I was a kid. We would go to Taco Bell, load up on burritos and hot sauce, and use the packets to clean pennies. The acidic hot sauce would eat off all the dirt and grime from the pennies, leaving shiny new pennies in their place. I wasn't sure how it all worked, but I loved to watch the brown dirty pennies get all clean and shiny.


Now I can show my kids the same cool trick. We started out with a handful of dirty pennies and a bowl of vinegar and salt. We placed our pennies one by one in the vinegar solution and then rubbed the grime off with q-tips.


So what's happening? After a while the copper in the pennies begins to react to the air to form copper oxide. When pennies are new the copper is bright and shiny, but the copper oxide changes them. It gives them a dull patina. The acid from the vinegar dissolves the copper oxide and makes them shiny and new again!

Here you can see where the vinegar has started to clean off the copper oxide. The brown parts are where the vinegar hasn't touched yet.
 
We experimented with other forms of acids to see how well they cleaned the pennies. We used lemon juice and salsa. Both cleaned the copper oxide off the pennies, although, I have yet to find something that cleans as well as the Taco Bell hot sauce.

Once all the pennies were clean we took them out of the vinegar and rinsed them off. Then we had bowls full of vinegar with copper oxide floating around in it. We rummaged around in the garage until we found these nails. We soaked the heads of the nails in our vinegar  and after about 10 minutes we had copper plated nails!


Happy President's Day!

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