Enthalpy of Vaporization

What is the Enthalpy of Vaporization?

The enthalpy of vaporization refers to the amount of energy required to transform a quantity of a liquid substance, or a solid, into a gas under consistent pressure.

The enthalpy of vaporization is a function of the pressure at which the transformation takes place.

This process is characterized by the following notation: ∆Hvap.

The ∆Hvap numerical value is expressed in Joule/mole and is equal to the increased internal energy of the vapor phase compared with the liquid phase, plus the work done against the ambient pressure.

In other words, the increase in the internal energy can be viewed as the energy required to overcome the intermolecular interactions (forces of repulsion or attraction between atoms) in the liquid, or solid in the case of sublimation.

What Process does ∆Hvap describe?

∆Hvap is the breakdown of intermolecular forces of a liquid, or solid, resulting in a change in the state of matter immediately to a gas (either evaporation or sublimation).

The breakdown of intermolecular forces of a liquid or solid is the result of a liquid or solid plus heat at a consistent ambient pressure.

The difference in internal energy between the vapor phase and the liquid or solid phase is expressed as a numerical value (____J/mol) and is referred to as the enthalpy of vaporization (∆Hvap).

How Does ∆Hvap Pertain to Vaping?

The ∆Hvapvalue pertains to vaping insofar as it perfectly describes the forces at work when we are “vaping” and refers to the exact amount of energy (heat) required to vaporize a liquid (e-liquid) or solid at a consistent ambient pressure.

This is important because it speaks to a major issue in the vaping industry which is that there is no consensus on the optimal temperature to vaporize an e-liquid, cannabinoids, glycerin, propylene glycol, flavouring, or nicotine.

Often, temperature ranges are given by the purveyors of these products, and the justifications for these suggested values are influenced by a number of factors including, but not limited to, the desired size of vape clouds, the strength of a single dose or draw, the decarboxylation of cannabinoids, the yield from a single draw (nicotine or cannabis), the longevity of the e-liquid, or efficiency of the vape device.

While these may be valid concerns, they should not be the determinants for the ideal temperature to vape either nicotine or cannabis.

Especially, when the enthalpy of vaporization of liquids is a settled science.

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