If we decrease the pressure of a substance, its boiling point decreases.

If we decrease the pressure of a substance, its boiling point decreases.

• A. False
• B. Not enough information
• C. Depends
• D. True

Answer: (D)

Boiling occurs when a liquid’s vapor pressure reaches the pressure surrounding it. If you lower the external pressure, the vapor pressure needed to reach boiling is achieved at a lower temperature, so the liquid boils at a lower temperature. This is why water boils at temperatures below 100°C at higher elevations where air pressure is lower. In general, decreasing pressure lowers the boiling point, so the statement is true.

Boiling occurs when a liquid’s vapor pressure reaches the pressure surrounding it. If you lower the external pressure, the vapor pressure needed to reach boiling is achieved at a lower temperature, so the liquid boils at a lower temperature. This is why water boils at temperatures below 100°C at higher elevations where air pressure is lower. In general, decreasing pressure lowers the boiling point, so the statement is true.