Which temperature does pure water boil at under standard conditions?

Which temperature does pure water boil at under standard conditions?

• A. 80°C
• B. 90°C
• C. 100°C
• D. 110°C

Answer: (C)

Boiling occurs when the liquid’s vapor pressure equals the surrounding pressure. At standard conditions, the surrounding pressure is 1 atmosphere (about 101 kPa). For pure water under that pressure, the temperature at which it boils is 100°C, when bubbles form throughout the liquid. The other temperatures would correspond to different pressures: lower pressures boil at temperatures below 100°C, higher pressures raise the boiling point above 100°C.

Boiling occurs when the liquid’s vapor pressure equals the surrounding pressure. At standard conditions, the surrounding pressure is 1 atmosphere (about 101 kPa). For pure water under that pressure, the temperature at which it boils is 100°C, when bubbles form throughout the liquid. The other temperatures would correspond to different pressures: lower pressures boil at temperatures below 100°C, higher pressures raise the boiling point above 100°C.