The penny turned silver because a layer of zinc was deposited on its surface through a chemical process.
The Science Behind the Silver Penny
When a copper penny undergoes a specific chemical reaction, it can appear to turn silver. This isn't magic, but rather a demonstration of chemistry in action. Here's a breakdown of the process based on the reference:
The Process: Zinc Coating
- The Setup: A copper penny is placed in a solution of sodium hydroxide and zinc dust.
- The Reaction: When heated, small amounts of zinc dissolve into the surface of the penny.
The Result: A Silver Appearance
The reference states that "When a copper penny is heated in a solution of sodium hydroxide mixed with zinc dust, small amounts of zinc dissolve into the surface of the penny. This causes the penny to look silver since there is now a layer of zinc over the outside of the penny." This zinc coating is what gives the penny its silvery appearance. So, the copper of the penny isn't actually changing; it's simply being covered by a thin layer of zinc.
