When water evaporates, which of the following best describes the change that occurs?

• A. Water freezes and becomes solid ice.
• B. Water molecules are broken down into hydrogen and oxygen gases.
• C. Water undergoes a physical change from liquid to gas.
• D. Water undergoes a chemical change and forms a new substance.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the process of evaporation. Evaporation is the change of a substance from the liquid phase to the gas phase at temperatures below the boiling point.
2. Step 2: Recognize that during evaporation, water molecules gain enough energy to overcome intermolecular forces and escape into the air as water vapor, but the molecular structure of H\_2O remains unchanged.
3. Step 3: Differentiate 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.
4. Step 4: Analyze the options: freezing water to ice is a physical change but not evaporation; breaking water into hydrogen and oxygen gases is a chemical change (electrolysis), not evaporation; forming a new substance implies a chemical change, which does not happen during evaporation.
5. Step 5: Conclude that evaporation is a physical change where water changes from liquid to gas without altering its chemical identity, so the correct description is that water undergoes a physical change from liquid to gas.