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Volatility (chemistry)

 

 
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Volatility (chemistry)
 
 
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Volatility in the context of chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and thermodynamics
Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
 is a measure of the tendency of a substance to vaporize. It has also been defined as a measure of how readily a substance vaporizes. At a given temperature, substances with higher vapor pressure
Vapor pressure

Vapor pressure , is the pressure of a vapor in Thermodynamic equilibrium with its non-vapor Phase s. All liquids and solids have a tendency to evaporate to a gaseous form, and all gases have a tendency to Condensation back into their original form ....
s will vaporize more readily than substances with a lower vapor pressure.

Although usually applying to liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
s, volatility can apply to solid
Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
 materials such as dry ice
Dry ice

Dry ice is solid carbon dioxide. It is commonly used as a versatile cooling agent.Dry ice Sublimation , changing directly to a gas at atmospheric pressure....
 (solid carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
) and ammonium chloride
Ammonium chloride

Ammonium chloride is, in its pure form, a clear white water-soluble crystalline salt of ammonia. The aqueous ammonium chloride solution is mildly acidic....
, which can change directly from solid to vapor
Vapor

A vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature.This means that the vapor can be condensation to a liquid or to a solid by increasing its pressure, without reducing the temperature....
 without becoming liquid.






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Volatility in the context of chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and thermodynamics
Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
 is a measure of the tendency of a substance to vaporize. It has also been defined as a measure of how readily a substance vaporizes. At a given temperature, substances with higher vapor pressure
Vapor pressure

Vapor pressure , is the pressure of a vapor in Thermodynamic equilibrium with its non-vapor Phase s. All liquids and solids have a tendency to evaporate to a gaseous form, and all gases have a tendency to Condensation back into their original form ....
s will vaporize more readily than substances with a lower vapor pressure.

Although usually applying to liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
s, volatility can apply to solid
Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
 materials such as dry ice
Dry ice

Dry ice is solid carbon dioxide. It is commonly used as a versatile cooling agent.Dry ice Sublimation , changing directly to a gas at atmospheric pressure....
 (solid carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
) and ammonium chloride
Ammonium chloride

Ammonium chloride is, in its pure form, a clear white water-soluble crystalline salt of ammonia. The aqueous ammonium chloride solution is mildly acidic....
, which can change directly from solid to vapor
Vapor

A vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature.This means that the vapor can be condensation to a liquid or to a solid by increasing its pressure, without reducing the temperature....
 without becoming liquid. The direct transition of a solid to a vapor is called sublimation
Sublimation (physics)

Sublimation of an element or compound is a transition from the solid to gas phase with no intermediate liquid stage. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below the triple point ....
.

Relation between vapor pressures and normal boiling points of liquids



Vapor pressure is the pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
 of a vapor which is in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid's tendency to evaporate. It is a measure of the tendency of molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s and atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s to escape from a liquid or a solid. A liquid's atmospheric pressure
Atmospheric pressure

Atmospheric pressure is sometimes defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere....
 boiling point corresponds to the temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point.

The higher the vapor pressure of a liquid at a given temperature, the higher the volatility and the lower the normal boiling point of the liquid.

The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids. As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points.

For example, at any given temperature, propane
Propane

Propane is a three-carbon alkane, normally a gas, but compressible to a transportable liquid. It is derived from other petroleum products during oil or natural gas processing....
 has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point (-43.7 °C), which is where the vapor pressure curve of propane (the purple line) intersects the horizontal pressure line of one atmosphere (atm
Atmosphere (unit)

The standard atmosphere is an international reference pressure defined as 101,325 Pascal and formerly used as unit of pressure . For practical purposes it has been replaced by the Bar which is 100,000 Pa....
) of absolute vapor pressure.

See also

  • Clausius-Clapeyron relation
    Clausius-Clapeyron relation

    The Clausius-Clapeyron relation, named after Rudolf Clausius and ?mile Clapeyron, who defined it sometime after 1834, is a way of characterizing the phase transition between two phases of matter, such as solid and liquid....
  • Distillation
    Distillation

    Distillation is a method of separation process mixtures based on differences in their Volatility in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
  • Fractional distillation
    Fractional distillation

    Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compound by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate....
  • Partial pressure
    Partial pressure

    In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
  • Raoult's law
    Raoult's law

    Established by Fran?ois-Marie Raoult, Raoult's law states:Once the components in the solution have reached chemical equilibrium, the total vapor pressure p of the solution is:...
  • Relative volatility
    Relative volatility

    Relative volatility is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes. In effect, it indicates the ease or difficulty of using distillation to separate the more Volatility components fro...
  • Vapor-liquid equilibrium
    Vapor-liquid equilibrium

    Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquid and its vapor are in Chemical equilibrium with each other, a condition or state where the rate of evaporation equals the rate of condensation on a molecular level such that there is no net vapor-liquid interconversion....
  • Vapor pressure
    Vapor pressure

    Vapor pressure , is the pressure of a vapor in Thermodynamic equilibrium with its non-vapor Phase s. All liquids and solids have a tendency to evaporate to a gaseous form, and all gases have a tendency to Condensation back into their original form ....
  • Volatile organic compound
    Volatile organic compound

    Volatile organic compounds are organic chemical compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the atmosphere....


External links

  • Definition of volatile from Wiktionary