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!

## Safety

### General Safety

General Safety

**For Laboratory Work:** Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).

**For Demonstrations:** Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.

#### Other Safety resources

RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies

## NGSS

Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models.

Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.

Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

Assessment is limited to chemical reactions involving main group elements and combustion reactions.

Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.

## Comments 6

## Hi Allison,

Hi Allison,

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

## Excellent Questions, Deanna!

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.

## Mass of Aluminum "thimbles"

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.

## Good Results!

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.

## img_0161.jpg

Thanks again!

## Al wire

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

## Save your lungs

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.