Aluminum - Copper Tradeoff

Materials

Bottle of Copper Chloride Solution (about 30g / Liter)

Aluminum Pie Plate (foil is too light & will disintegrate during the reaction) 

1 Liter Glass Graduated Cylinder

Gloves and Goggles

Procedure

1. Cut a strip from an aluminum pie pan. Twist into an interesting shape and put in graduated cylinder. (It is best to wedge it tightly into the cylinder so it will remain submerged when the copper chloride solution is added).
2. Pour the copper chloride solution into the cylinder.
3. The aluminum will go into solution and the copper sill precipitate out, leaving the reddish precipitate on the aluminim foil.

Reaction

This demonstration is a replacement reaction in which the more active metal, aluminum, replaces the copper ions in solution.

2Al(s) + 3Cu²⁺ (aq) --> 2Al³⁺ (aq) + 3Cu(s)

NOTES

• During this reaction, three observations of a chemical reaction may be made:
  1. The copper chloride solution changes color from green-blue to almost colorless;
  2. The reaction evolves heat;
  3. A new colored solid forms.
• Encourage students to write their observations. Help them to avoid saying that the aluminum "turned to a new substance" or that it "rusted."
• The spongy copper that forms on the surface of the aluminum can be identified bacause it will not react with hydrochloric acid.
• The spongy copper can be fused by a hot flame to form the more recognizable metallic copper. Take the copper to a welding facility.

QUESTIONS FOR STUDENTS

1. Identify three changes to indicate that this is a chemical reaction.
2. What change has taken place in the copper atoms that reacted?
3. What change has taken place in the aluminum atoms?
4. Will any other metal react in a similar way when placed in a solution of copper chloride?