Name: __________________________________________________________________ Date: __________________
Striking It Rich Lab
Introduction
Seeing is believing – or so it is said. In this investigation, you will change the appearance of some
pennies through chemical and heat treatment.
An alchemist was a combination of magician and metallurgist who tried unsuccessfully to convert
common metals into gold. The craft flourished from ancient times until the 18th century. Alchemists were
not early chemists, as some people believed, but their practical knowledge about elements and compounds
contributed to the work of the earliest true chemists. Like the alchemists, you will not turn copper into
gold, but by allowing the copper in a penny to mix with zinc under certain conditions, you may create an
interesting ALLOY, or homogeneous physical mixture of two or more metals, of these two metals. The
Saquajawea dollar coin is an ALLOY of five different metals - copper, zinc, tin, manganese, and nickel.
Although it looks as if it were comprised of one metal, it is simply a physical mixture of these metals.
Mixtures in which the various parts are indistinguishable from one another are called HOMOGENEOUS
MIXTURES, OR SOLUTIONS. Some commonly used alloys are bronze, which is a mixture of copper and tin,
and brass, which is a mixture of copper and zinc.
Procedure
1. Obtain 3 pennies. Use steel wool to clean each penny until it is shiny. Record the appearance of the
pennies in Data Table 1.
2. Set aside one of the cleaned pennies to serve as a control; that is, an untreated sample that can be
compared later to the other two treated coins.
3. Weigh a 2.0-2.2 g sample of granulated zinc or zinc foil. Place it in a 250 mL beaker.
4. Use a graduated cylinder to measure 25 mL of 1 M zinc chloride (ZnCl2) solution. Add the solution to
the beaker that contains the zinc metal. (Caution: 1 M zinc chloride solution can damage skin. If any
accidentally spills on you, notify your teacher immediately; wash the affected area with tap water.)
5. Cover the beaker with a watch glass and place it on a hot plate. Gently heat the solution until it just
begins to bubble, then lower the temperature just to sustain gentle bubbling. Do not allow the
solution to boil vigorously or become heated to dryness.
6. Using forceps or tongs, carefully lower two clean pennies into the solution in the beaker. To avoid
causing a splash, do not drop the coins into the solution. Put the watch glass on the beaker and
keep the solution boiling gently for ten minutes. You should notice a change in appearance of the
pennies during this time.
7. Using forceps or tongs, remove the two coins from the beaker. Rinse them under running tap water,
then gently dry them with a paper towel. Set one treated coin aside for later comparisons and use
the other treated coin in the next step.
8. Using tongs, place one of the pennies from step seven in the Bunsen burner flame until you see a
color change. Remove the penny from the flame, rinse with tap water, and dry with a paper towel.
9. Observe and compare the appearance of the three coins. Record your observations in Data Table 1.
Name: ______________________________________ Date: ____________ Period: ________ Pg#: _______
Data
Data Table 1. Observations of Coins
Condition
Appearance
Untreated Penny
Penny treated with Zn and ZnCl2
Penny treated with Zn, ZnCl2, and place in
Bunsen burner flame
Conclusion Questions
1. A. Compare the color of the three coins – untreated (the control), heated in the zinc chloride
solution only, and heated in the zinc chloride solution and then heated in the Bunsen burner flame.
B. Do the treated coins appear to be composed of metals other than copper? If so, explain.
2. If someone claimed that a pure gold and silver penny was produced in this investigation, how would
you decide if this was correct?
3. Identify at least two practical unique uses for metallic changes similar to those you observed in this
investigation.
4. Identify the following half reactions as reduction or oxidation.
Z2+ + 2 e-  Zn
_________________________
Cu  Cu2+ + 2 e-
_________________________
5. In this experiment, copper and zinc were fused to create an alloy of brass. Describe what an alloy is.
6. What are some other examples of alloys?