Question

1. rust forming on a piece of iron is an example of which of the following:

a. a violation of the laws of physics because new mass has been created.
b. the natural process of decay as metallic ions age.
c. a chemical change because oxygen atoms from the atmosphere bonded with the iron atoms.
d. a physical change because the process can be reversed.

Explanation:

• Option A: Rusting doesn't violate physics laws. Mass isn't "created"; it's just redistributed in a chemical reaction (iron + oxygen → rust).
• Option B: Rusting isn't "metal aging" in a biological - like decay sense. It's a chemical reaction between iron and oxygen.
• Option C: Rusting is a chemical change. Iron (\(Fe\)) reacts with oxygen (\(O_2\)) in the air. The chemical equation for rusting (a simplified form of iron oxidation) is \(4Fe + 3O_2

ightarrow 2Fe_2O_3\) (rust). New substances (iron oxides) are formed with different chemical properties than pure iron.

• Option D: Rusting is not a physical change. Physical changes don't form new substances. Rust (\(Fe_2O_3\)) is a new substance with different properties than iron. And while some rust removal processes exist, they involve chemical reactions (e.g., using acids to dissolve rust) rather than reversing the rusting process in a simple, non - chemical way.

Answer:

C. a chemical change because oxygen atoms from the atmosphere bonded with the iron atoms.