what is the boiling point of a substance?
Boiling is the process in which liquids turn into vapour (water turns into water vapour at a temperature of 100 degrees centigrade). The boiling point of a substance is the temperature at which the vapor pressure of the liquid becomes equal to the surrounding pressure.
Depending on the substance and its surrounding pressures, the boiling point of a liquid can vary significantly. This is because when the surrounding pressures are lower, the boiling point of a liquid is also lower.
The normal boiling point of a compound is the temperature at which one atmosphere of pressure is equivalent to its vapor pressure. This was defined by IUPAC in 1982.
Compounds with a higher boiling point can still exist as a liquid or solid at that given temperature, provided their vapors are contained. Hence, it is important to determine the boiling point of a compound to help in its recognition and characterization.
Boiling points can also be used to differentiate between pure and impure substances. Generally, a pure substance has a distinct melting point, while mixtures of two or more chemicals often have a unified melting temperature range.
The boiling point of a compound can be measured using a thermometer. This is done by bringing a sample of the substance to a temperature below the boiling point, and measuring the amount of heat required to transform the sample into a liquid.