What is reached when the vapor pressure of a liquid equals atmospheric pressure at its surface?

The boiling point of a liquid is defined as the temperature at which its vapor pressure equals the atmospheric pressure surrounding it. At this temperature, the liquid transitions into its gaseous state. When the vapor pressure equals atmospheric pressure, bubbles of vapor can form within the liquid, allowing it to boil. This is a critical concept in both fire protection and emergency services, as understanding the behavior of combustible liquids at varying temperatures can inform safety protocols during fires and hazardous material incidents.

In contrast, the evaporation point does not involve the entire liquid reaching a specific temperature; it occurs at any temperature when molecules at the surface gain enough energy to escape into the vapor phase. The condensation point refers to the temperature at which a gas transitions back to a liquid. The melting point is the temperature at which a solid becomes a liquid, which is not relevant to the context of vapor pressures. Thus, boiling point is the correct answer as it specifically relates to the conditions under which boiling occurs due to the balance of vapor pressure and atmospheric pressure.