Chemistry 1: Gold, Silver and Melting Penny Lab
Alchemy: Can you turn a penny into gold?
Seeing is believing – or so it is said. The modern practice of chemistry started with the
study of alchemy in medieval Europe and the Middle East. Alchemists convinced people that by
doing certain chemical reactions, you could turn cheap metals into gold. The alchemist would
sell them the secret and by the time anyone realized that the “secret” didn’t work, they’d be long
gone with the money.
In this activity you will observe how the properties of metal can be changed. Copper
(Cu), the familiar metal of pennies, will be changed in properties by heating it with Zinc (Zn) in
the presence of a solution of zinc chloride (ZnCl2).
Prelab: Do your lab report on a separate sheet with the following order:
1. Title
2. Purpose
3. Safety - fill in the important safety issues.
4. Materials - read procedure and make a list what materials you need.
5. Data table - Read procedure and make your own inference on data you would require.
Procedure Part 1:
1. Obtain three pennies. Clean pennies in a lemon juice/salt mixture if they are
tarnished.
2. Assemble a ring stand with a ring clamp and wire gauze. Place a beaker on the wire
gauze and surround the beaker with a second ring clamp so that the beaker is
prevented from tipping over.
3. Weigh a 0.5 g sample of granulated zinc. Pour it into beaker.
4. Carefully pour into beaker 20 mL of 0.5 M Zinc Chloride solution.
5. Heat the beaker gently with the Bunsen burner until the solution just begins to bubble.
Then adjust the burner flame to continue gently bubble.
CAUTION: DO NOT ALLOW THE SOLUTION TO BOIL. (Replace the water if too much
evaporate)
6. Using forceps or tongs, carefully add two pennies to the hot ZnCl2 solution. Measure
their mass before drop in the solution. Record the masses. Do not drop the coins into
the solution so that you cause splash. Set the 3rd penny aside as a control-an untreated
sample that can be compared with the treated coins.
7. Observe and record any changes in the appearance of the coins until no further
changes are noted.
8. Fill one beaker with distilled water.
9. With forceps or tongs, remove the two pennies from the solution. Place them in the
beaker of distilled water. Remove heat from the beaker of ZnCl2, but do not discard
the solution.
10. Using forceps or tongs, remove the coins from the beaker of water. Rinse them under
running tap water. Dry the coins with paper towel. Set one treated coin aside to be
used for later comparisons. Measure treated coins’ masses again and record after
reaction. Mass must be changed.
11. Gently heat the other treated, dried coin in the outer cone of burner flame, holding it
vertically with the forceps or tongs.
12. Continue heating the coin for three seconds after its appearance changes. Do not
overheat it. It turns gold if you do this right. Immediately immerse the coin in the
second beaker of distilled water. Record your observations.
13. Remove the coin from the beaker of water. Dry it with a paper towel. Observe the
appearance of the three pennies and record your observation in the data table.
14. Clean up: Ask your teacher before act.
Disposal of ZnCl2: After it has cooled, carefully pour the solution into the sink. Rinse
down the drain with water.
Disposal of Zinc: Once ZnCl2 is out of the dish, pour a little water into the dish, swirl,
and drain. Rinse with water again and drain. Use paper towels to wipe the zinc and
place it in container where it was.
Procedure Part 2:
15. Test the melting point of Zinc and copper by holding a new (after 1983) penny, in a
Bunsen burner flame. Be sure to tilt the burner so the metal does not drip into it. Only
heat the penny to the flexible point. Not to the dripping point. Cool the penny in
water. Heat again and cool slowly. Record observation. Especially how long it takes
to be flexible.
16. Try to repeat step 1 with an old (before 1982) penny.
17. To a different new penny – use triangular file to scratch off outer Cu layer. Make
observations. Note the thickness of the Cu.
18. Clean Table: Wash the table with water and paper towels. Wash your hands.
ANALYSIS QUESTIONS: Use Complete Sentences!!
1. Compare the color of the three coins (untreated, heated in zinc chloride solution,
heated in zinc chloride solution and in burner flame). Do any of the treated coin
appearances remind you of other metals?
2. How could you verify whether you had changed the copper metal to another metal?
(List at least 3 methods)
3. List some (3 or more) practical uses for the metallic changes you observed in this
activity?
4. What happened to the copper atoms originally present in the treated pennies? {Were
the copper atoms used up or destroyed or covered up?}
5. What was the “silver” color made of?
6. What was the “gold” color made of?
7. Explain what you learned about the new pennies vs old pennies in Part 2?
8. Make a connection between element’s physical property (melting points) and
locations of the periodic table. For example, why copper and zinc have different
melting points.
9. Calculate how many atoms of Zn covered the coin. Use your mass data.