Final answer:
A copper coin made to look silver undergoes a chemical reaction when dipped into a silver nitrate solution. Copper atoms are oxidized, releasing electrons to reduce silver ions to solid silver, which coats the coin. The total mass of the system remains constant, though the coin gains the mass of the added silver.
Step-by-step explanation:
When a copper coin is made to look silver, the process is typically a chemical reaction where the copper reacts with silver nitrate. During this reaction, copper atoms donate electrons to silver ions, and the silver ions are reduced to silver atoms which coat the copper surface, giving it a silver appearance. This process is described by the half-reactions of oxidation and reduction, occurring simultaneously.
In the reaction, the copper metal is oxidized to copper (II) ions, which dissolve into the solution, often turning it blue. Simultaneously, the silver ions receive electrons and are reduced to solid silver which precipitates and forms a layer on the copper coin. While there is a mass change on the coin due to the silver deposit, it should be noted that the total mass of the copper coin and the newly deposited silver remains constant, as mass is conserved in chemical reactions. However, the coin itself will indeed be heavier due to the added mass of silver.
This phenomenon can be observed when a piece of copper is immersed in a silver nitrate solution. As the solution turns blue, indicative of the presence of copper ions, the copper develops a gray, silver-colored coating due to the deposition of solid silver atoms.