Boiling point is reached when the vapor pressure of the liquid equals what?

Boiling point is reached when the vapor pressure of the liquid equals what?

• A. Internal vapor pressure
• B. External pressure
• C. Atmospheric humidity
• D. Liquid weight

Answer: (B)

Boiling occurs when the vapor pressure of a liquid reaches the pressure exerted on it by its surroundings. As temperature rises, the liquid’s vapor pressure increases. When it becomes equal to the external pressure (such as atmospheric pressure), bubbles form throughout the liquid and it boils. This is why boiling point depends on ambient pressure: higher external pressure means a higher temperature is needed, while lower external pressure lowers the boiling temperature. The other ideas don’t set the boiling point: internal vapor pressure isn’t a defined external pressure, humidity doesn’t determine the liquid’s vapor pressure, and the liquid’s weight doesn’t affect the temperature at which vapor pressure matches the surrounding pressure.

Boiling occurs when the vapor pressure of a liquid reaches the pressure exerted on it by its surroundings. As temperature rises, the liquid’s vapor pressure increases. When it becomes equal to the external pressure (such as atmospheric pressure), bubbles form throughout the liquid and it boils. This is why boiling point depends on ambient pressure: higher external pressure means a higher temperature is needed, while lower external pressure lowers the boiling temperature. The other ideas don’t set the boiling point: internal vapor pressure isn’t a defined external pressure, humidity doesn’t determine the liquid’s vapor pressure, and the liquid’s weight doesn’t affect the temperature at which vapor pressure matches the surrounding pressure.