thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...

, the bubble point is the

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

(at a given

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

) where the first bubble of

vapor In physics, a vapor (American English) or vapour (Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R ...

is formed when heating a

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

consisting of two or more components. Given that vapor will probably have a different composition than the liquid, the bubble point (along with the

dew point The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to produce a relative humidity of 100%. This temperature depends on the pressure and water content of the air. When the air at a temperature above the ...

) at different compositions are useful data when designing distillation systems. For a single component the bubble point and the dew point are the same and are referred to as the

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

Calculating the bubble point

At the bubble point, the following relationship holds:
:

\sum_^ y_i = \sum_^ K_i x_i = 1

where
:

K_i \equiv \frac

. K is the ''distribution coefficient'' or ''K factor'', defined as the ratio of mole fraction in the vapor phase

\big(y_\big)

to the mole fraction in the liquid phase

\big(x_\big)

at equilibrium.
When

Raoult's law Raoult's law ( law) is a relation of physical chemistry, with implications in thermodynamics. Proposed by French chemist François-Marie Raoult in 1887, it states that the partial pressure of each component of an ideal mixture of ''liquids'' is ...

and

Dalton's law Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This empirical law was observed by John ...

hold for the mixture, the K factor is defined as the ratio of the vapor pressure to the total pressure of the system:
:

K_i = \frac

Given either of

x_i

y_i

and either the temperature or pressure of a two-component system, calculations can be performed to determine the unknown information.

References

{{Reflist Temperature Phase transitions Gases

Calculating the bubble point

See also

References