The key difference between evaporation and vaporization is that evaporation of a liquid occurs at a temperature that is below the boiling point of that liquid, whereas vaporization occurs at the boiling point of the liquid.
Both evaporation and vaporization refer to processes in which a liquid converts into its gaseous phase. Although evaporation occurs only in liquids, vaporization can occur in solids as well; we call this sublimation (conversion of solid phase directly into the gas phase without going through a liquid phase).
CONTENTS
1. Overview and Key Difference
2. What is Evaporation
3. What is Vaporization
4. Side by Side Comparison – Evaporation vs Vaporization in Tabular Form
5. Summary
What is Evaporation?
Evaporation is the conversion of a liquid into its gaseous phase at a temperature that is below the boiling point of the liquid. The molecules in a liquid have different kinetic energies. When we provide energy from outside to the liquid (such as heat), the kinetic energy of these liquid molecules increase. When the energy is enough for the molecules in the surface to overcome the intermolecular forces between them, the molecules tend to escape the surface and convert into gas state.
Figure 01: Evaporation Occurs at the Surface of the Water
However, some of the molecules that enter the gas phase through evaporation can rejoin the liquid via condensation. This makes up an equilibrium between the evaporation rate and the condensation rate. Moreover, constant vapour pressure is established in this stage. If we increase the temperature of the liquid at this points, it leads to an increase in the rate of evaporation since the kinetic energy of the molecules increases. Therefore, the amount of molecules occupying the space above the liquid increases.
What is Vaporization?
Vaporization is the conversion of a liquid phase into a gas phase at the boiling point of the liquid. Therefore, vaporization occurs at the boiling temperature of the liquid.
Figure 02: Boiling Water
In order to boil a liquid, the vapour pressure of the liquid should be equal to the external pressure surrounding the liquid. This means the molecules at the surface of the liquid should have a kinetic energy that is sufficient to overcome the intermolecular forces between the liquid molecules; therefore, these molecules can leave the liquid by converting into the gas phase.
What is the Difference Between Evaporation and Vaporization?
Evaporation and vaporization are processes where a liquid substance is converted into its gaseous phase. The key difference between evaporation and vaporization is that evaporation of a liquid occurs at a temperature that is below the boiling point of that liquid, whereas vaporization occurs at the boiling point of the liquid. Moreover, evaporation occurs when the vapour pressure of the liquid is lower than the external pressure surrounding the liquid while vaporization occurs when the vapour pressure of the liquid is equal to the external pressure.
Furthermore, during evaporation, the molecules at the surface of the liquid leave first while vaporization can occur at any location of the liquid (that is why we can see bubbling of water at the bottom of the container when heating it).
Summary – Evaporation vs Vaporization
Both evaporation and vaporization refer to processes in which a liquid substance converts into its gaseous phase. The key difference between evaporation and vaporization is that evaporation of a liquid occurs at a temperature that is below the boiling point of that liquid, whereas vaporization occurs at the boiling point of the liquid.
Reference:
1. Helmenstine, Todd. “Heat of Vaporization Example Problem.” ThoughtCo, Jan. 29, 2020, Available here.
2. Helmenstine, Anne Marie. “Evaporation Definition in Chemistry.” ThoughtCo, Jan. 29, 2020, Available here.
Image Courtesy:
1. “Vaporization” By Tristan Schmurr (CC BY 2.0) via Flickr
2. “Boiling water in pan” By Appliance City (CC BY 2.0) via Flickr