What is defined as the temperature at which the vapor pressure of a liquid equals or exceeds the atmospheric pressure?

The boiling point is the temperature at which the vapor pressure of a liquid matches or exceeds the surrounding atmospheric pressure. At this point, the liquid can transform into vapor. As temperature rises, molecules in the liquid gain kinetic energy and begin to move more freely. When the vapor pressure reaches atmospheric pressure, bubbles form within the liquid, leading to boiling.

This concept is crucial in hazardous materials operations, as many substances can emit vapors that pose health risks or contribute to explosive environments at or below their boiling points. Understanding this temperature helps responders anticipate changes in the state of the hazardous materials they might encounter.

The other terms refer to different phenomena: the melting point relates to the transition from solid to liquid, the freezing point is concerned with the transition from liquid to solid, and critical temperature refers to the temperature above which a substance cannot exist as a liquid regardless of pressure. Each of these definitions serves a distinct purpose in physical chemistry and material handling, underscoring why the boiling point is specifically significant in the context of vapor and pressure dynamics.