1.The alchemist's dream. Talk about alchemy as you do the experiment.
2.Place very shiny pennies in hot 3M NaOH and powdered zinc solution (IN THE HOOD). A hot plate is used, keep solution near boiling temperature. Brand new shiny pennies work great.
Pennies remain in solution 3 to 5 minutes until pennies appear to be completely silver. Talk about the difference between pre-1982 and post-1982 pennies and how we make silver and gold pennies as follows.
Pre-1982 pennies contain a much greater percentage of copper. Post-1982 pennies are mostly zinc. Show the broken penny which is mostly zinc inside. Show them a copper, "silver" and "gold" penny. Talk about how the zinc atoms on top of the copper atoms make the pennies look silver. How do we make the "gold" pennies? We heat the pennies in the flame of a Bunsen burner. As we heat the silver penny the atoms move. The zinc atoms move in between the copper atoms. Help students visualize this be putting one of your hands on top of your other hand the show that if heat makes your fingers move it allows fingers from one hand to move in between the fingers of your other hand. Copper and zinc atoms make brass and looks like gold. Ask if anyone plays a saxophone or a trumpet? These are made of brass.
3. Remove "silver" pennies from solution using tongs and rinse them in water (use 600 mL beaker of water to cool pennies).
The pennies are zinc plated and appear silver in color. Small chunks of zinc are usually stuck on the penny. Students take a penny to the sink and in the tub of water they use their hands to remove all the zinc chunks, until the penny is totally clean.
SAFETY: Do NOT dry the pennies with paper towels. Small pieces of zinc on a paper towel can ignite and cause a fire in the lab.
4. Students take their penny to a Bunsen burner. They use tongs to pick up one penny at a time (the tongs are positioned on the edges of the penny). Adult supervision is required anytime a Bunsen burner is on.
Heat zinc plated copper pennies in the flame of a Bunsen burner. Turn the penny in the flame as it heats. The zinc and copper atoms form brass. The copper and zinc atoms merged to produce "gold" pennies.
SAFETY: Remove from heat immediately when yellow color appears and submerge the penny and tongs in the beaker of water located next to the Bunsen burner. This will cool the tongs and the penny so no one gets hurt.
I am a passionate expert in the field of chemistry, with a deep understanding of various chemical reactions and experimental procedures. My knowledge extends to the fascinating realm of alchemy, a historical precursor to modern chemistry. Allow me to guide you through the alchemist's dream and the transformation of ordinary pennies into silver and gold.
The alchemical experiment described involves the use of a hot 3M NaOH and powdered zinc solution, conducted in a controlled environment (in the hood) with the aid of a hot plate. The objective is to turn shiny pennies into silver and gold replicas. Let's delve into the key concepts and elements involved:
-
Alchemy: Alchemy is an ancient philosophical and proto-scientific tradition that aimed to transform base metals into noble metals, such as gold or silver. It also sought the discovery of an elixir of life and a universal panacea. While alchemy laid the groundwork for modern chemistry, it often involved symbolic language and mystical elements.
-
Chemical Composition of Pennies:
- Pre-1982 Pennies: These contain a higher percentage of copper.
- Post-1982 Pennies: These are mostly composed of zinc. The distinction between these two types is crucial for the experiment, as the properties of copper and zinc play a central role.
-
Silver and Gold Pennies:
- Silver Pennies: The pennies are placed in a solution, and the zinc atoms from the powdered zinc solution move between the copper atoms on the surface, giving the appearance of silver.
- Gold Pennies: By heating the silver pennies in the flame of a Bunsen burner, the copper and zinc atoms merge to form brass, resembling gold. The heating causes atoms to move, and zinc atoms interlace with copper atoms, creating a brass-like appearance.
-
Safety Measures:
- The experiment involves handling hot solutions, so safety precautions include using tongs, adult supervision when using a Bunsen burner, and cooling the pennies in water to avoid injuries.
- Emphasize the importance of not drying the pennies with paper towels due to the risk of small zinc pieces causing a fire.
-
Zinc Plating Process:
- Pennies are zinc plated during the experiment, giving them a silver color. The small zinc chunks on the penny need to be removed in water to ensure a clean and safe result.
-
Brass Formation:
- Heating the zinc-plated copper pennies in the Bunsen burner flame causes the zinc and copper atoms to merge, forming brass and creating the illusion of gold.
This engaging and hands-on experiment not only showcases the principles of alchemy but also provides a practical understanding of chemical reactions, metal properties, and the importance of safety in a laboratory setting.
