Mr. Weber and I have been working on a project that has to do with the Periodic Table of Elements. As part of this big investigation, we decided to work on an experiment about copper pennies and their reaction with air. First, we collected a bunch of materials: pennies (old ones, that had reacted with the oxygen in air to produce copper oxide), nails, paper clips, vinegar, salt, a cup and spoon.
Once we’d collected our materials, we poured some vinegar in a cup, and then mixed a lot of salt into it – until we had full saturation (when no more salt would mix in.) Then we dipped one penny in, half way, to see how it would react. What happened? The half that was in the liquid turned totally shiny! Why did this happen? The vinegar dissolved the copper oxide that had been on the exterior of the penny, and left us with just the shiny copper exposed. Then we dumped in a bunch of pennies, and stirred them up for about a minute. All the pennies turned shiny, and the vinegar turned kind of grey, because it had all the copper oxide from the pennies mixed into it.
We took out all the new-looking pennies, and split them into sections: one section we rinsed off very carefully with water, and then we just left the other section non-rinsed. We wanted to wait to see if there would be a difference between these two groups.
With the left-over vinegar, we mixed in the shiny, new paper clips and nails. The paper clips and nails turned very dull and dark, because the copper oxide that had been left in the vinegar, was attracted to the new metal of the clips and nails.
After coming back a week later, the pennies that had been left non-rinsed were dull and had turned greenish in colour. That’s what happens when the copper, oxygen, and chlorine (from the salt) combine – speeding up the oxidation process. You can see this same process happening on the Statue of Liberty, or on the copper pipes on the sides of St. George’s Junior School. The rinsed-off pennies stayed pretty shiny and new-looking. We know, though, that over time, these pennies will react again with the air, and form a layer of copper oxide on their exteriors, turning them dull. Check out the pictures which display the results of our experiment: