Material Science, Percent Comp and Copper

Soda Can in Copper(II)Chloride

What are we doing to help kids achieve?

     Years ago, I took some wonderful material science workshops sponsored by ASM International. They did an amazing job of helping me add some more tools to my teaching tool kit. Materials are all around us and the workshop was a week long adventure into either creating a material science course or tying material science into existing curriculum. The chemistry of materials can easily be introduced into any curriculum.  

     One experiment I remember was creating a "vein" of copper. The person put some dirt (sand) in a tube, added some copper(II)chloride, placed in more sand and then put a nail through all three layer and capped it. I attempted to recreate the experiment and found it worked well with a little added water.

     It made the idea of a copper mine more "visible". The next question is, how do we know if we should dig it up?  A "Chemistry in the Commuity" book years ago had a great percent composition problem. Here is a version of it.

"There are two copper bearing minerals...Azurite which is
2CuCO3·Cu(OH)2 and Tennantite which is Cu12As4S13.   

Which has more copper by mass percent?"

     This is a fun problem. The big misconception is that the tennantite has more copper because of the subscript.  However, when students find the percent by mass, the azurite is the winner. So if you were digging up copper, which mineral would you want and why?

     After percent composition problems, we then start talking about types of reactions. A classic single displacement reaction is copper (II) chloride with aluminum. Years ago, I am not sure where or when, I saw someone sand the paint off of a soda can, empty the soda, fill it with water and placed it carfully in a solution of copper (II) chloride.  The results are dramatic. After a day, the blue solution fades, solid copper forms on the can and if you carefully hold the can up students can see the thin interior plastic liner that is coats the aluminum in the can (something few people have seen or bother to look at...). This is a great time to talk about material science. Do you think it matters how we store chemicals? What happens if we are not carefull or do not pay attention to chemical properties? What would happen if all pop cans did not have plastic liners? Students start to get the point and really like this demonstration. Do you have a neat experiment that has multiple applications? Please share....I would love to hear from you...