Penny Lab - or, Copper, Silver, Gold
Objective: In this lab we will explore interactions of metals and observe the formation of an alloy.
1M Zinc Chloride solution - caution - can damage skin. If contacted, rinse promptly
Zinc metal Pennies
250 mL Beaker watch glass
Hot Plate Graduated Cylinder
Tongs, forceps, scoopula
Safety: Goggles, closed toe shoes, aprons recommended. Caution: burning hazard: don’t touch hot plate;
don’t touch hot pennies – they stay hot a long while. Cool under running water if desired.
1) Clean three pennies – use steel wool if necessary, then wipe off with acetone and then touch only
2) Save one as control - use to compare later
3) Measure 25 mL of Zinc Chloride into 250 mL beaker using 100 mL graduated cylinder
4) Weigh 2 g of granular zinc and add to the zinc chloride in the beaker
5) Cover beaker with watch glass (round side down) and then heat solution on hot plate to boiling
6) Add two pennies to boiling solution with forceps or tongs - do not splash (note - if both partners
want pennies to keep, add four.)
7) Carefully turn pennies from time to time using forceps, and/or end of scoopula. Do not splash
liquid, get burnt by steam or hot plate, and do not knock over and break beaker. When change is
complete, take pennies out, rinse in water, and dry gently on a paper towel.
8) Save one penny, take the other and lay it on the hot plate. Watch closely, and as soon as the color
change is complete, take off with forceps. Overheating will cause pennies made after 1982 to melt.
9) Using beaker tongs, pour waste into 1000 mL beaker on bench shelf and rinse beaker in sink.
1) List your observations - what appearance changes do you see?
2) Is this an example of an alchemical change (making one element from another)? Why or why not?
3) Identify at least two practical uses for the changes you saw (on pennies or something else).
4) Do you think you could get the pennies to "go back" to copper color? How?