Which of the following could be considered a chemical change?

• A. Breaking a glass window
• B. Iron rusting when exposed to air
• C. Water freezing to form ice
• D. Salt dissolving in water

Answer: (B)

Verified step by step guidance

1. Understand the definition of a chemical change: it involves the formation of one or more new substances with different chemical properties from the original substances.
2. Analyze each option to determine if a new substance is formed:
3. Breaking a glass window is a physical change because the glass is only physically broken into pieces, but its chemical composition remains the same.
4. Water freezing to form ice is a physical change because it is a change in state (liquid to solid) without altering the chemical identity of H\_2O.
5. Salt dissolving in water is a physical change because the salt dissociates into ions but does not chemically react to form a new substance.
6. Iron rusting when exposed to air is a chemical change because iron reacts with oxygen and moisture to form a new compound, iron oxide (rust), which has different properties from iron.