Thursday, September 9, 2010

Pretty as a Penny

     For this project I chose to use a penny because it is an unique object, but also one that is often seen in ones life. I was also very curious to see what affects certain chemicals had on the penny, therefore I observed some physical properties of a penny and some chemical properties as well. My results were as follows:

Physical Properties:
weight: before 1982 a penny weighed 13.1 g and after 1982 it weighed 12.5 g. The reason for this weight difference is because the composition is different between 1982 and present day pennies. Pennies made from 1944-1982 were made out of 95% copper and 5% zinc. Pennies made from 1982-2010 are/were made out 2.5% copper and 97.5% zinc. Thus concluding copper is heavier than zinc.
volume of 1982-2010 pennies: 360mm3.
color: copper brown 
circumference: 19mm
smell: copper iron smell (alike blood) 
density: pre 1982: 3.11g post 1982: 2.50g
diameter: 19mm
radius: 9.5mm  

Discovering Chemical Properties through making Chemical Reactions 
For the first experiment to test the chemical properties of the penny Katherine and I placed a  2010 penny and a penny before 1982  between two layers of the paper towel, which were coated in vinegar. We let the pennies sit between the layers over night. When we checked the pennies in the morning we discovered that a chemical reaction had occurred. The copper reacted with the vinegar creating a green compound called copper acetate on the top of the penny and heavily around the edges. After researching we learned that that the green residue is also on the statue of liberty, except the statue of liberty is copper sulfate. 

When we soaked the pennies in clorox bleach we discovered that a similar chemical reaction occurred when we soaked the pennies in vinegar. A green residue also formed when they were soaked in bleach. Although we do not have proof that this was also the formation of copper acetate. However, there was less green crust on the outside of the penny when it was soaked in bleach than when it was soaked in vinegar.

In our third experiment we decided to soak the pennies in water  and leave them over night. Both rusted however, the older penny rusted mores so than the newer one. 

For the fourth experiment we soaked the pennies in jewelry cleaner which polished both pennies. Who knew that underneath all that dirt the older penny was almost as shiny as the 2010 penny?

Our last and final experiment is somewhat incomplete. We had heard that if you soaked a penny in coke that eventually the penny would disintegrate and be "eaten" completely by the coke. Fascinated by that we tried it. We discovered that after a day of soaking not much had change. We think that there was a slight change in the size and shape of the penny, but we are unsure if the change was accurate. Katherine and I plan to continue the coke experiment, because we feel that over time it will eventually happen, and we are determined to discover the answer.

Work Cited:


  1. It was really helpful that you added the information about the different weights of the pennies before and after 1982 and that you experimented with pennies from different dates. The physical properties were really well done and the chemical properties were very detailed. It would have been a little easier to understand if you made the chemical reaction of each experiment more obvious, but overall you did a really good job. The blog was neat, organized, and easy to follow!

  2. I really liked you blog. It was really cool and creative to do the experiments with different dated pennies, it gives a lot more information to look at! I also liked all the different physical properties you had. It tell us a lot of data that helps us understand you chemical properties. Your chemical changes and reactions were really interesting! It was a very good idea to take pictures of both pennies to show us the difference, and you explained the changes and differences of both very well. Good Job!!!

  3. Emily- your blog is fantastic. That layout is nice and easy to read. The pictures are great, close enough to see the differences in the pennies after the experiments. Good job on citing your information that you got off the internet. Each of your chemical experiments shows a rational thought process to it and explains the experiment well and describes what happened to the penny. With the coke I would have left it in for a longer period of time to see what would happen to it, or if you could not do this find proof that the myth was either true or false. Also I would have tried to explain what had changed with the penny no matter how minor it might have been. Great job!