Boiling occurs when the vapor pressure equals the atmospheric pressure.

Boiling occurs when the vapor pressure equals the atmospheric pressure.

• A. Vapor pressure is greater than atmospheric pressure
• B. External pressure is irrelevant
• C. Vapor pressure is less than atmospheric pressure
• D. Vapor pressure equals the atmospheric pressure

Answer: (D)

Boiling happens when the vapor pressure of the liquid matches the pressure of its surroundings. As you heat a liquid, its vapor pressure increases. When it reaches the surrounding atmospheric pressure, bubbles of vapor can form inside the liquid and rise to the surface, so the liquid boils. If the vapor pressure is still below atmospheric, only surface evaporation occurs. If the vapor pressure exceeds atmospheric, boiling is already underway, but the defining moment is the equality of the two pressures.

Boiling happens when the vapor pressure of the liquid matches the pressure of its surroundings. As you heat a liquid, its vapor pressure increases. When it reaches the surrounding atmospheric pressure, bubbles of vapor can form inside the liquid and rise to the surface, so the liquid boils. If the vapor pressure is still below atmospheric, only surface evaporation occurs. If the vapor pressure exceeds atmospheric, boiling is already underway, but the defining moment is the equality of the two pressures.