What is the relationship between boiling and vapor pressure?

Boiling occurs when the vapor pressure of a liquid equals the atmospheric pressure.

In more detail, boiling is a process where a liquid turns into a gas. This happens when the temperature of the liquid increases to a point where its particles have enough energy to overcome the atmospheric pressure acting upon the surface of the liquid. This specific temperature, at which a liquid boils, is known as its boiling point.

Vapor pressure, on the other hand, is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. It is a measure of the tendency of molecules or atoms to escape from a liquid or a solid. The higher the vapor pressure of a substance at a given temperature, the higher the volatility and the lower the normal boiling point of the substance.

The relationship between boiling and vapor pressure is therefore direct. When a liquid is heated, its vapor pressure increases. When the vapor pressure equals the atmospheric pressure, the liquid starts to boil. This is because the pressure exerted by the molecules escaping from the liquid equals the pressure exerted by the air molecules pushing down on the liquid's surface.

For example, water boils at 100 degrees Celsius at sea level, where the atmospheric pressure is standard. However, at higher altitudes where the atmospheric pressure is lower, water boils at a lower temperature. This is because the vapor pressure of the water doesn't need to overcome as much atmospheric pressure in order to start boiling.

In summary, the boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure. The relationship between boiling and vapor pressure is therefore a crucial concept in understanding phase transitions in Chemistry.