Which statement about water's physical properties is correct?

• A. Water boils at 100°C and freezes at 0°C
• B. Water boils at 90°C and freezes at -10°C
• C. Water boils at 110°C and freezes at 10°C
• D. Water has no boiling point

Answer: (A)

At standard atmospheric pressure, water changes state at fixed temperatures: it freezes at 0°C and boils at 100°C. The boiling point is the temperature at which liquid water becomes water vapor when the surrounding pressure equals 1 atm, and the freezing point is where liquid water becomes ice. So saying water boils at 100°C and freezes at 0°C matches these well-known values under typical lab conditions. The other statements give temperatures that don’t align with water’s phase-change points at 1 atm—for example, water would still be liquid at 90°C, and it would be ice at -10°C. Also, water does have a boiling point (it does not have “no boiling point” at any given pressure).