Cu Again: A Copper Cycle
Introduction
Chemical reactions are often accompanied by formation of a precipitate, evolution of
gas, change in color, or pronounced temperature change. In this activity, you will
observe these characteristics of chemical reactions and observe some copper
compounds. Enjoy the variety!
Purpose
To recognize that change of state, change in color, formation of a precipitate, or the
evolution of heat are associated with a chemical change; to study reactions and
compounds of copper.
Safety
Wear protective glasses and an apron at all times. Tie back hair. Wear closed
13. toed
shoes.
Avoid skin contact with solids and solutions. Dispose of all solutions in the waste
container provided by your teacher. Wash your hands before leaving the laboratory.
Add the safety that is included in the procedure
Materials: Read the Procedure and list the materials.
Procedure: First, prepare a data table. Record what you see throughout the laboratory activity.
1. Your teacher will demonstrate for the class the reaction of metallic
copper with concentrated nitric acid, HNO3. This must be done in the
fume hood. (Caution: Avoid breathing poisonous gases. Avoid contact
of skin with nitric acid. It burns skin and clothing.) The products
formed are copper(II) nitrate solution, Cu(NO3)2(aq), and nitrogen
dioxide gas, NO2(g). Record observations.
2. A solution of copper(II) nitrate was prepared earlier. Half fill a thinstem pipet with this solution. Transfer all of the solution to your
labeled test tube.
3. Half fill another thin-stem pipet with sodium hydroxide solution,
NaOH(aq). (Caution: Avoid contact with sodium hydroxide; it burns
skin.) Add this slowly to the test tube. Add another portion of NaOH.
This reaction may give off heat. Touch the test tube to observe this.
Record observations.
4. Use a glass stirring rod to mix the solutions, well from top to bottom.
5. Add about 1/3 of a pipet of distilled water. Stir to mix. The solid
material is copper(II) hydroxide, Cu(OH)2(s).
6. Place your test tube in a hot water bath. Remove the test tube when
you see no further change occurring. Record observations. This
product is copper(II) oxide, CuO(s). Run cold water over the outside
of the test tube to cool it.
7. Bring the tube to the centrifuge for your teacher to spin the solution.
Use the pipet labeled “waste” to remove the clear liquid (supernatant
liquid) above the copper(II) oxide. Do not remove any of the solid. Put
the liquid in the waste container.
8. Add about half a pipet of distilled water. Stir to mix. Centrifuge the
solid again. Then remove and discard the liquid, in the waste
container.
9. To the precipitate, add hydrochloric acid, HCl, from the final thinstem pipet. (Caution: Avoid contact of both skin and clothing with
hydrochloric acid.) Stir to mix. All the solid must dissolve. Add more
HCl if needed. This new product is copper(II) chloride solution,
CuCl2(aq). Record observations.
*****Grading: Prep(Title, Purpose, Safety, Materials, Procedure, Data Table) = 10; Data = 10;
Data Analysis =14;
Imp/App = 6
Total = 40 points
10. Add a precut piece of aluminum wire (3-4 pieces) to the test tube. Place
the test tube in a cold water bath. This reaction could be fast or take a
time! Be sure to use a test tube holder to hold the test tube since the
reaction gives off considerable heat. The products forming in this step are
hydrogen gas, H2(g), aluminum chloride solution, AlCl3(aq), and metallic
copper, Cu(s). Record observations.
11. The blue color will be gone when the reaction is finished. Remove and
discard the colorless liquid, in the waste container.
12. Wash the solid with half a pipet of distilled water. Discard the liquid.
Wash the solid again with half a pipet of fresh distilled water, and place
the solid on a filter paper over funnel while you holding it waste
container.
14. Use tweezers to remove any leftover pieces of aluminum wire. Observe
the final product.
15. Take the paper towel with your product and a spatula to the fume hood,
with your lab partners. Your teacher will test a small sample of your
product with concentrated nitric acid. Record observations.
16. Clean the pipets and test tube. Return the wire, pipets and test tube to the
designated locations.
17. Clean the countertop. Put away equipment. Wash hands thoroughly
before leaving the laboratory.
__________________________________________
Data Analysis
and Concept
Development
1.
Cu
(solid)
CuCl2
2.
3.
4.
Cu(NO3)2
CuO
5.
6.
Use your observations to complete a drawing similar to
the one to your left. Alongside each arrow, write in the
chemicals used. Also near each arrow, write in key
words to convey what you saw.
As chemical changes occurred, what observations did
you note? List the observations that alerted you that
some type of chemical change was occurring.
Did each reaction show all of the kinds of changes you
listed above? For each step, use your observations to
justify your answer.
What happened to the hydrogen gas generated in the
last reaction? Add hydrogen gas to the cycle.
What happened to the aluminum chloride? Show this
on the cycle.
What did you enjoy most about this activity?
Cu(OH)2
__________________________________________
Implications and
Applications
1.
2.
3.
Reread the title of this laboratory activity. Why is this
series of reactions often called the “copper cycle”?
How did the last part of the procedure (Step 15)
complete the cycle?
Recycling is one important way to conserve precious
natural resources.
a) What common metals have you observed being
collected for recycling?
b) Think about all types of materials that you know are
recycled. Compose a list of the materials.
c) What types of materials might prove too difficult or
costly to recycle?