Which of the following best describes what happens to water when it freezes?

• A. Water undergoes a chemical change, forming a new substance with different chemical properties.
• B. Water decomposes into hydrogen and oxygen gases.
• C. Water undergoes a physical change, turning from a liquid to a solid without altering its chemical composition.
• D. Water evaporates and becomes a gas.

Answer: (C)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form of a substance but not its chemical composition, while a chemical change results in the formation of new substances with different chemical properties.
2. Recall the process of freezing water: When water freezes, it changes from liquid to solid (ice) due to a decrease in temperature, but the molecular structure of H\_2O remains the same.
3. Analyze the options given: Freezing does not break water molecules into hydrogen and oxygen gases, so decomposition is incorrect; it also does not involve evaporation, which is a phase change from liquid to gas.
4. Conclude that freezing water is a physical change because the chemical identity of water remains unchanged, only its physical state changes from liquid to solid.
5. Therefore, the best description is that water undergoes a physical change, turning from a liquid to a solid without altering its chemical composition.