Which phase change occurs for water at 100 °C under standard atmospheric pressure?

• A. Liquid water boils to become water vapor
• B. Ice melts to become liquid water
• C. Water vapor condenses to become liquid water
• D. Liquid water freezes to become ice

Answer: (A)

Verified step by step guidance

1. Identify the temperature and pressure conditions given: 100 °C and standard atmospheric pressure (1 atm).
2. Recall the phase change temperatures of water at 1 atm: ice melts at 0 °C, and liquid water boils at 100 °C.
3. Understand that at 100 °C and 1 atm, water reaches its boiling point, where it changes from liquid to gas (water vapor).
4. Recognize that boiling is the phase change from liquid to vapor, so water will boil and become water vapor at this condition.
5. Conclude that the correct phase change is liquid water boiling to become water vapor.