Give Me Back My Copper! A Simple, but Multi-Faceted Lab Activity to Review Lab Skills in Week One of AP Chemistry

copper lab

In the lab, students are given a 1.5 gram samples of copper. The copper is taken through a series of five chemical reactions ending with the precipitation of solid copper. After the five reactions, students are asked to return their 1.5 gram samples of copper to the teacher.

My dear friend and fellow AP chemistry teacher suggested that I use this lab during the first week of AP chemistry to review and reinforce lab techniques, for example, making solutions, diluting solutions, and decanting liquids. The experience prepared students for kinetics, equilibrium, and titration labs to come. 

Here is a brief overview of the lab, and you’ll find my co-worker’s lab instructions attached.

Conversion 1: Convert copper turnings to copper(II) nitrate

Students dilute 15.8 M nitric acid to 8 M. They then react the given copper turnings with the diluted acid. Warning! Nitrogen dioxide, a brown gas, is released, which requires using the fume hood. When the reaction is complete, students will have a beautiful, blue solution of copper(II) nitrate.

Skills: measurement, dilution, selection of appropriate glassware, selection of appropriate tools for measurement, use of the fume hood

Conversion 2: Convert copper(II) nitrate to copper(II) hydroxide

Using pH paper or litmus paper, students test the copper(II) nitrate solution. Then, they make a solution of 6 M NaOH and test the solution with pH paper or litmus paper. The reaction of copper(II) nitrate and NaOH is slowly performed in an ice-water bath. Students use the indicator to test the progress of the reaction. The reaction is complete when the pH paper or litmus paper color matches the NaOH’s test result. The reaction forms a pale blue precipitate, copper(II) hydroxide.

Skills: using indicator paper, measurement, making a solution, selection of appropriate glassware, selection of appropriate tools for measurement, and set up and use of an ice water bath

Conversion 3: Convert copper(II) hydroxide to copper(II) oxide

Students wash the blue precipitate with distilled water and heat the mixture to a gentle boil. The heat initiates the decomposition of the hydroxide compound forming a black, solid copper(II) oxide. When the oxide cools, students decant any remaining liquid and wash twice with distilled water.

Skills: measurement, using hot plates, and proper decanting

Conversion 4: Convert copper(II) oxide to copper(II) chloride

Students dilute a solution of hydrochloric acid to 6 M. The solution is poured over the copper(II) oxide causing an instantaneous change. The black sludge-like solid dissolves, leaving a crystal-clear green solution. Students love this conversion!

Skills: dilution and measurement

Conversion 5: Convert copper(II) chloride to copper

Students add small amounts of aluminum to displace the copper from solution. As the solution returns to a colorless liquid, students remove any unreacted aluminum and decant the fluid. The resulting copper is washed with distilled water and transferred to a watch glass. The product is dried in the drying oven and mass when cool and dry.

Skills: collection of product, use of drying oven, and measurement

 

A special thanks to Karen Heiges, our fellow AP chemistry teacher, who allowed me to share her work. Do you have a lab activity to share? Please post ideas as we finish this AP year and begin looking ahead. Do you have ideas for adding particle-level modeling to the lab? I look forward to reading your thoughts!

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Comments 6

Deanna Cullen's picture
Deanna Cullen | Tue, 05/03/2016 - 08:47

Hi Allison,

 When you say "thimble" in conversion five, is that actually a sewing thimble? Looking forward to trying this out!

Allison Tarvin's picture
Allison Tarvin | Thu, 05/05/2016 - 17:22

 A local drug testing company went out of business and donated supplies to our lab.  The "aluminum thimbles" look exactly like sewing thimbles, and they are 100% aluminum.  I'm not really sure what the drug testing industry uses them to do!  I'll get a mass of the Al tomorrow and post it.  

Allison Tarvin's picture
Allison Tarvin | Tue, 05/10/2016 - 08:09

The mass of a single Al thimble is 0.8290 grams on the analytical balance.  The thimbles are glorified Al foil.  I suspect that a similar mass of foil would react similarly.

Deanna Cullen's picture
Deanna Cullen | Tue, 05/10/2016 - 14:30

Thanks for this! I just used the lab with my AP students now that the AP exam is over. I wanted to pilot it before I use it next year. I plan to use your suggestion and have students complete the lab very early in the curriculum next year. 

I used aluminum wire since I did not have thimbles. The wire worked just fine. The students seemed to enjoy the lab and the challenge of getting a good percent yield. Groups that used good practices earned good results. A couple of groups had more than 5% error, but I had witnessed bad practices that clearly explained the error.  

Thanks again!

Allison Tarvin's picture
Allison Tarvin | Wed, 05/11/2016 - 14:44

I'm glad to know that the wire worked.  We won't have this box of thimbles forever!

John Yohe | Wed, 05/11/2016 - 14:34

If you set up conversion one in a flask with tubing to allow the nitrogen gas to flow into a second beaker of water, that will capture the gas (reforms dilute nitric acid). When the beaker starts cooling, the pressure will be lower in the first flask with the copper turnings, which will cause the water to be pushed back into the first flask, diluting your copper nitrate.

This will allow you to do the experiment without a fume hood.  Here is a link to Flinn's version of that step: https://www.flinnsci.com/media/621474/91624.pdf

We do a similar lab to look for evidence of chemical change using aluminum wire and it works well.