Sean fell while riding his green bicycle last year. He bent the fender and scratched the paint down to the metal. Sean’s bicycle was outside all winter and now is beginning to rust where the fender is damaged. Which evidence tells Sean that a chemical change is taking place on his bike?

Answer 1

The evidence that suggests a chemical change is taking place on Sean's bike is the formation of rust. Rusting occurs when iron (in the metal of the bike) reacts with oxygen in the presence of moisture, resulting in the formation of iron oxide. This reaction is a chemical change because it alters the chemical composition of the metal, resulting in a new substance (rust) that has different properties from the original metal. The appearance of rust indicates that a chemical change has occurred, as it cannot be reversed simply by physical means.