What is defined as the temperature at which a liquid's vapor pressure equals atmospheric pressure?

The temperature at which a liquid's vapor pressure equals atmospheric pressure is known as the boiling point. At this temperature, the liquid begins to transition into a gas, allowing bubbles of vapor to form within the liquid itself. This process occurs because the vapor pressure, which is the pressure exerted by the vapor in equilibrium with its liquid, reaches a level high enough to overcome the atmospheric pressure pressing down on the liquid.

Understanding the boiling point is crucial in many applications, including cooking, chemical processing, and environmental science, because it dictates the conditions under which a substance changes from liquid to gas. Different substances have different boiling points, determined by their molecular structure and intermolecular forces.

The other terms—freezing point, melting point, and condensation point—are related to different phase changes and do not describe the specific condition of vapor pressure equalizing with atmospheric pressure. This clarification reinforces the distinct characteristics of phase transitions among solids, liquids, and gases, helping to fully grasp the concept of boiling in the context of hazardous materials and their handling.