Penny Skin Lab

Name ______Date ______Per ______

Penny Skin Lab Goal:  To categorize a penny as a homogeneous or heterogeneous mixture.

Background Information: In 1982, the U.S. Mint changed the composition of pennies from mostly copper to mostly zinc with a thin copper coating. Zinc has a melting point around 400 C and copper has a melting point around 1000 C. A lab burner can reach temperatures around 900 C, enough to melt zinc but not hot enough to melt copper.

Materials: penny, file, tongs, lab burner, goggles, metal tray Safety: Always wear goggles. Do not allow the molten zinc to splatter on bare skin. Allow the zinc to cool completely before handling.

Procedure:  Use the file to score opposite sides of the penny until you see a silvery color appear.

 Light the burner and adjust it to get a hot flame. Tilt the burner at a 45 degree angle.

 Hold the penny with the tongs and place it into the hot flame.

 When the zinc inside melts, allow it to drip out of the penny shell onto the tray.

 Do NOT handle the zinc or the penny shell until you are sure it has cooled sufficiently. Conclusion: What type of mixture is a penny? Use your observations to explain your answer in at least 5 complete sentences. ______