The tarnishing of silver is a chemical change. This occurs when silver reacts with sulfur compounds in the air, forming silver sulfide, which appears as a dark coating on the silver surface.
In a physical change, the substance might change in appearance, shape, or state, but its chemical identity remains the same. However, in the case of tarnishing, the actual composition of the silver changes because the silver ions react chemically with sulfide ions to form a new compound.
Once tarnished, the silver cannot simply return to its original state by physical means, such as wiping it clean. It requires a chemical process, such as polishing or using special cleaners, to remove the tarnish and restore the silver’s shine. This distinct alteration in composition and the necessity for a chemical reaction to reverse it firmly classify tarnishing as a chemical change.