Final answer:
The temperature at which the vapor pressure of a liquid equals the atmospheric pressure is the boiling point. It's known as the normal boiling point when this temperature is measured at a surrounding pressure of 1 atm.
Step-by-step explanation:
The temperature at which the vapor pressure of a liquid becomes equal to the atmospheric pressure is called the boiling point. At this temperature, bubbles of vapor form throughout the liquid, leading to the rapid evaporation or boiling of the liquid.
The normal boiling point of a liquid is the specific temperature at which it boils when the surrounding pressure is exactly 1 atm (101.3 kPa).
Water, for example, has a normal boiling point of exactly 100°C (373 K) under these conditions.