Which of the following is an example of a chemical reaction?

• A. Iron rusting to form Fe2O3
• B. Water freezing to form ice
• C. Salt dissolving in water
• D. Breaking a glass bottle

Answer: (A)

Verified step by step guidance

1. Understand the definition of a chemical reaction: it involves the rearrangement of atoms to form new substances with different chemical properties.
2. Analyze each option to see if new substances are formed: for example, iron rusting involves iron reacting with oxygen to form iron oxide (Fe2O3), which is a new compound.
3. Consider water freezing to form ice: this is a physical change where water changes state from liquid to solid, but the chemical composition (H2O) remains the same.
4. Evaluate salt dissolving in water: this is a physical process called dissolution, where salt dissociates into ions but no new chemical substances are formed.
5. Look at breaking a glass bottle: this is a physical change involving breaking the glass into smaller pieces without changing its chemical composition.