Final answer:
Silver tarnishes due to a chemical reaction with hydrogen sulfide gas which produces silver sulfide on the surface. Removing tarnish involves special polishes that can also remove some silver, and tarnishing is a specific form of corrosion.
Step-by-step explanation:
When silver is not polished often, it will tarnish due to a chemical reaction. Tarnish is the result of silver reacting with hydrogen sulfide gas in the air, which may be produced by various sources including industrial processes or the decay of organic materials. The chemical reaction can be described with the word equation: 2 Ag + H₂S → Ag₂S + H₂. Silver sulfide, commonly known as tarnish, creates dark and streaky black discoloration on the surface of silver objects.
The tarnish can be challenging to remove, and the process usually involves special polishes that contain complexants specific to silver, such as thiourea. Unfortunately, these polishes also remove a small layer of silver along with the tarnished material, meaning that repeated cleaning over time can result in loss of material from the silver object.
Corrosion is a broader term that refers to the deterioration of metals through oxidation; tarnishing is a specific type of corrosion that affects silver. While some metals may rust or develop a patina, silver tarnishes, forming black silver sulfide as a distinctive sign of this process. Protecting silver from tarnish involves regular cleaning and sometimes the use of specially designed agents that protect the metal from the elements.