What does the boiling point signify for a substance?

The boiling point of a substance signifies the temperature at which it transitions from the liquid phase to the gas phase. This occurs when the vapor pressure of the liquid equals the atmospheric pressure surrounding it, allowing bubbles of vapor to form within the liquid and rise to the surface. At this point, the liquid becomes a gas throughout the entire mass of the liquid, not just at the surface.

Understanding this concept is crucial in thermodynamics and physical chemistry, as it relates not only to how substances behave under different temperature and pressure conditions but also to practical applications such as distillation, atmospheric science, and material safety. The boiling point is specific to each substance and can be influenced by external pressure, which explains why liquids boil at lower temperatures at higher elevations.