What liquid changes the color of a penny faster vinegar or saltwater?

Vinegar is an acidic liquid, while saltwater is a basic liquid. Acids react with metals to form salts, and this reaction is what causes the penny to change color. The copper in the penny reacts with the vinegar to form copper acetate, which is a blue-green salt. The reaction between vinegar and copper is much faster than the reaction between saltwater and copper, which is why vinegar changes the color of a penny faster than saltwater.