Rust will form as Iron reacts with Oxygen over time. Which of the following is evidence that a chemical reaction has occurred?

Question

A. Oxygen is present

B. Iron oxide, a new substance is produced

C. The shape of the metal changes

D. The state of matter remains the same

Answer 1

B. Iron oxide, a new substance is produced. This is evidence that a chemical reaction has occurred. The formation of iron oxide, commonly known as rust, is a chemical process where iron reacts with oxygen in the presence of water or moisture to form a new substance with different chemical properties than the original iron. The other options do not necessarily indicate a chemical reaction has occurred. Oxygen may be present without any reaction taking place, the shape of the metal may change due to physical changes like bending or breaking, and the state of matter may remain the same during a chemical reaction (i.e. solid iron reacting with gaseous oxygen to form solid iron oxide).