When a nail rusts, what type of change has occurred?

• A. Chemical change
• B. Phase change
• C. Mechanical change
• D. Physical change

Answer: (A)

Verified step by step guidance

1. Understand the definitions of the types of changes: A physical change affects the form of a substance but not its chemical composition, while a chemical change results in the formation of one or more new substances with different properties.
2. Recognize that rusting involves iron reacting with oxygen and moisture in the environment to form iron oxide, which is a new substance.
3. Identify that since rusting produces a new substance with different chemical properties, it is not just a change in appearance or state.
4. Conclude that rusting is a chemical change because it involves a chemical reaction and the formation of a new compound.
5. Note that phase change refers to changes between solid, liquid, and gas states, and mechanical change involves physical forces altering shape or size without changing composition, so these do not apply to rusting.