Vapor Pressure

Boiling Point, and Normal Boiling Point

What is vapor pressure?

Vapor pressure is the pressure that a gas of a substance exerts on the container of that substance. The value of the amount of vapor pressure depends on the temperature. If the temperature increases the vapor pressure increases and vise versa. Vapor pressure can be calculated from the total gas volume and the mass of the substance vaporized. The pressure doesn't depend on anything else except temperature. It is the indication of the evaporation rate of a substance.


Boiling Point

Boiling point is the temperature where a substance changes from a liquid to a gas at a certain pressure. Boiling point correspondes with the temperature where vapor pressure equals the surrounding environmental pressure. It increases with the increase of pressure up to the critical point where gas and liquid properties are the same. Boiling point depends on where you are at sea level. Down at a lower pressure or below sea level will make the boiling point lower and it won't take as long to boil water. But if you go to a higher sea level then it will be higher and take longer to boil.

Normal Boiling Point

Normal boiling point is where the vapor pressure of a liquid equals the defined atmospheric pressure at sea level. Waters boiling point at sea level is 100 degrees celsius. This is that pressure because it is the temperature at which the vapor pressure is at 760 mmHg (millimeters of mercury) or one atm (atmosphere).