Final answer:
In the given sentence, 'tarnish' is used as a verb. It refers to the chemical reaction where silver reacts with sulfur compounds in the air, forming silver sulfide that darkens the silver surface. Removing tarnish with polish also results in a slight loss of silver.
Step-by-step explanation:
In the sentence "Silver will tarnish if it is not polished often," the word "tarnish" acts as a verb. As a verb, it describes the action that happens to silver when it is exposed to sulfurous gases in the air and not maintained properly. The reaction between silver and sulfur compounds, specifically hydrogen sulfide gas, leads to the formation of silver sulfide, commonly known as tarnish, which causes the surface of silver items to become dark and streaky black.
Chemical Reaction of Silver Tarnishing
The tarnishing process can be represented by a word equation: 2Ag + H2S → Ag2S + H2. This indicates that silver metal reacts with hydrogen sulfide to form silver sulfide and hydrogen gas. While the tarnish can be removed using various polishes, this process invariably removes a small amount of silver along with the tarnish.