Which of the following is the BEST evidence that rusting is a chemical property rather than a physical property of iron? Rust can form on any iron. Rust forms slowly. Rust cannot turn back into iron. Rust does not look the same as iron
The Correct Answer and Explanation is:
The best evidence that rusting is a chemical property rather than a physical property of iron is:
Rust cannot turn back into iron.
Explanation:
Rusting is a chemical reaction in which iron reacts with oxygen and water to form iron oxide (rust). This process involves a change at the molecular level, where new substances are formed, and the iron itself is chemically altered. The key to understanding why rusting is a chemical property lies in the fact that once rust has formed, it is not possible to reverse the process and return the rusted iron back to its original metallic form. This irreversibility indicates that a chemical change has taken place.
In contrast, physical properties involve changes that do not alter the chemical identity of the substance. For example, if you bend, crush, or stretch iron, these are physical changes because the iron remains iron and no new substance is formed. Similarly, the color or texture of a material can change, but as long as the chemical structure stays the same, it’s considered a physical property.
Rusting, on the other hand, forms a new substance (iron oxide) with different properties than the original iron. Iron oxide has different physical and chemical properties from iron, such as a different color, texture, and reactivity. The fact that rust cannot be undone, or that iron cannot be recovered from rust without going through a complex chemical process (like reduction in a furnace), confirms that rusting is a chemical change.
Thus, rusting involves a transformation of the material into a new substance, which is the hallmark of a chemical property rather than a physical one.
