Of state. Contents and Concepts 1. Comparison of Gases, Liquids, and Solids Changes of State

Boiling Point and Melting Point

The temperature at which the vapor pressure of a liquid equals the pressure exerted on the liquid (atmospheric pressure, unless the vessel containing the liquid is closed)

is called the boiling point of the liquid. As the temperature of a liquid is raised, the vapor pressure increases. When the vapor pressure equals the atmospheric pressure, stable bubbles of vapor form within the body of the liquid (Figure 11.8). This process is called boiling. Once boiling starts, the temperature of the liquid remains at the boiling point (as long as sufficient heat is supplied). Because the pressure exerted on a liquid can vary, the boiling point of a liquid can vary. For instance, at 1.00 atm (the average atmospheric pressure at sea level), the boiling point of water is 100_C. But at 0.83 atm (the average atmospheric pressure in