Tarnishing of silver is a chemical change. It occurs when silver reacts with sulfur compounds in the air or other substances, forming a thin layer of silver sulfide on the surface. This chemical reaction alters the composition of the silver, resulting in a darkening or discoloration that cannot be easily reversed by physical means. 1 2
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Key Takeaways: Is Silver Tarnishing a Physical or Chemical Change?
- Silver tarnishing is a chemical change as it involves a reaction between silver and substances in the environment, resulting in the formation of silver sulfide.
- Tarnishing occurs due to the interaction between silver and sulfur compounds, leading to a chemical transformation at the molecular level.
- Unlike physical changes, tarnishing cannot be easily reversed by physical means and demonstrates the irreversible nature of the chemical reaction.
Why is silver tarnishing a chemical change?
Silver tarnishing is a chemical change because it involves a reaction between silver and substances in the surrounding environment, leading to the formation of a new compound on the surface of the silver. 3 This change is not reversible and alters the composition and properties of the silver.
When silver tarnishes, it reacts with sulfur compounds present in the air, such as hydrogen sulfide (H2S), to form a blackish layer of silver sulfide (Ag2S) on the surface of the silver. This process is known as oxidation.
The silver sulfide layer is different in composition and appearance from the original silver, and it cannot be easily removed by physical means like wiping or washing. 4
The chemical reaction between silver and sulfur compounds is responsible for the tarnishing process. It occurs due to the transfer of electrons between the silver atoms and the sulfur compounds, resulting in the formation of a new compound with different chemical properties.
This change is irreversible, as the silver atoms have bonded with sulfur atoms to form silver sulfide. The tarnished silver may lose its luster and appear dull or discolored, demonstrating the alteration of its physical and optical properties. Therefore, silver tarnishing is considered a chemical change.
Why is silver tarnishing not a physical change?
Silver tarnishing is not a physical change because it involves a chemical reaction between silver and substances in the environment, resulting in the formation of a new compound with different chemical properties. Physical changes, on the other hand, only affect the physical appearance or state of a substance without altering its chemical composition. 5 6
When silver tarnishes, it undergoes a chemical reaction with sulfur-containing compounds, such as hydrogen sulfide or sulfur dioxide, in the air. This reaction leads to the formation of silver sulfide (Ag2S) on the surface of the silver object.
Unlike physical changes, such as melting or bending, where the substance retains its chemical identity, silver tarnishing involves a transformation at the molecular level.
During the tarnishing process, the silver atoms react with sulfur atoms from the surrounding environment to form silver sulfide. This reaction occurs due to the transfer of electrons between the silver and sulfur atoms, resulting in the creation of a new compound with different properties than pure silver.
The formation of silver sulfide changes the chemical composition and properties of the silver object, making it distinct from its original state.
In summary, silver tarnishing is not a physical change because it involves a chemical reaction that alters the composition and properties of the silver. It is a result of the interaction between silver and sulfur-containing compounds in the environment, leading to the formation of silver sulfide and demonstrating the characteristics of a chemical change.
Further reading
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Is Baking Bread a Physical or Chemical Change?
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Is Freezing Exothermic or Endothermic?
Is Evaporation Endothermic or Exothermic?
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References
- Institute, C. C. (n.d.). Understanding how silver objects tarnish – Canada.ca. Understanding How Silver Objects Tarnish – Canada.ca. https://www.canada.ca/en/conservation-institute/services/training-learning/in-person-workshops/understanding-silver-tarnish.html
- JCE staff. (2000, March). Silver to Black – and Back. Journal of Chemical Education, 77(3), 328A. https://doi.org/10.1021/ed077p328a
- Tarnish – Wikipedia. (2019, April 1). Tarnish – Wikipedia. https://en.wikipedia.org/wiki/Tarnish
- Brunning, A. (2013, December 16). Removing Tarnish from Silver. Compound Interest. https://www.compoundchem.com/2013/12/16/removing-tarnish-silver/
- Changes in Matter: Physical vs. Chemical Changes. (n.d.). Changes in Matter: Physical Vs. Chemical Changes. https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes
- Physical & Chemical Changes in Matter – Teachers (U.S. National Park Service). (n.d.). Physical & Chemical Changes in Matter – Teachers (U.S. National Park Service). https://www.nps.gov/teachers/classrooms/physical-chemical-changes-in-matter.htm