If water boils at 100 °C at 1 atm pressure, which of the following statements is correct?

• A. At higher altitudes, water boils at a temperature higher than 100 °C.
• B. At higher altitudes, water boils at a temperature lower than 100 °C.
• C. The boiling point of water is always 100 °C, regardless of pressure.
• D. Water cannot boil below 100 °C under any circumstances.

Answer: (B)

Verified step by step guidance

1. Understand that the boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure.
2. Recall that at 1 atm pressure, water boils at 100 \( ^\circ C \).
3. Recognize that at higher altitudes, atmospheric pressure is lower than 1 atm.
4. Since boiling occurs when vapor pressure equals external pressure, a lower external pressure means water will boil at a lower temperature.
5. Therefore, at higher altitudes, water boils at a temperature lower than 100 \( ^\circ C \).