Chemical Reactions
Lab: Gold Rush!
Name ______________________
Period ____
PROBLEM
Is turning pennies into silver and then gold an example of a chemical reaction?
HYPOTHESIS
If turning pennies into silver then gold is a chemical reaction, then it will change colors because
copper does that when mixed with the zinc solution.
MATERIALS
250ml Beaker
3 Copper pennies
Ring Stand
Salt/Vinegar Solution
50ml Beaker
Bunsen Burner
Evaporating Dish
Tongs
Balance
Distilled water
3 M NaOH
Zn granular
Tweezers
Goggles
PROCEDURES
1. Get materials. Wear a long sleeved shirt/ lab coat, rubber gloves, and goggles throughout the entire experiment.
2. Place 20ml of sodium chloride/vinegar solution in a clean, 50ml beaker.
3. To clean the cooper pennies, place them in the above solution for 5 minutes.
4. Remove the pennies and rinse them thoroughly with tap water. Dry with a towel.
5. Mix together .5g of zinc, granular, and 30ml of 3M sodium hydroxide solution in a clean evaporating dish.
6. Using a ring stand set up with a Bunsen burner, carefully and gently heat the mixture to steaming.
Do not allow the solution to boil or splatter.
7. Using tweezers, immerse 3 pennies in the mixture until they get completely coated with "silver". You may want
to flip the pennies partway through.
8. Use tweezers to remove the pennies. CAUTION: THE PENNY WILL BE VERY HOT. Carefully dip the pennies
into the 250ml beaker of distilled water. Shine the pennies with a towel. The pennies should now appear silver.
9. Using tweezers, heat one penny in a burner flame until the penny turns gold. Immediately dip the penny
into a beaker of distilled water. The penny will be extremely hot and should be handled with tweezers
until it has cooled for several minutes.
10. Using tweezers, heat the remaining penny in a burner flame until one side of the penny turns gold.
Immediately dip the penny into a beaker of distilled water. The penny will be extremely hot and should be
handled with tweezers until it has cooled for several minutes.
11. When done, using tongs, bring your evaporating dish containing NaOH and Zn granules to the front sink.
DATA
Zinc
+
Zn
+
sodium hydroxide
yields
2NaOH
Sodium zincate
Na2ZnO2
+
+
Oxygen gas
H2
CONCLUSION
When turning a penny into silver, a copper reaction is taking place. When a copper penny is added
to the sodium zincate solution, the zincate ions (ZnO2) migrate to the copper where they are decomposed
and reduced to metallic zinc. The silver color produced is due to the metallic zinc coating the penny.
When the zinc-coated penny is heated, the penny becomes gold in color. The gold color is due to
the zinc and copper combining to form base.
Brass is a copper-zinc alloy. An acid is a mixture of two or more metals (or a metal and a non-metal
fused together) dissolved in each other when molten.