Praxis II General Science (5435) Practice Test

Silver tarnishing is an example of a chemical change because it involves a chemical reaction between silver and sulfur compounds in the atmosphere, resulting in the formation of silver sulfide. This process alters the chemical structure of the silver, producing a new substance with different properties. In contrast, breaking a glass, melting ice, and boiling water are all physical changes. These processes do not change the chemical identity of the substances involved; they merely alter their physical state or appearance. For example, when ice melts to become water, or when water boils to become steam, the molecules remain H2O in both liquid and gaseous states, signifying that no new substances are formed. Thus, the transformation that occurs when silver tarnishes is a clear indication of a chemical change, as it results in a substance with unique characteristics and properties.