Evaporation vs Vaporization
Though the two processes, evaporation and vaporization, sound similar in meaning, there is some difference between vaporization and evaporation. When we closely look at those two processes at molecular level, we can realize that these two processes have distinct features and they are not identical. Both evaporation and vaporization take place in liquids by escaping molecules from the liquid phase to its gas phase, but in two different ways. Vaporization is a surface process whereas the evaporation is a bulk process. In this article, we will discuss the features in each process and compare them in order to find the differences between vaporization and evaporation in terms of how they occur and what are the special features in the process. Moreover, this focuses on the factors that affect the evaporation and vaporization and how those factors change the rate of each process.
What is Vaporization?
Vaporization is a spontaneous process which occurs at the surface of a liquid. It is the conversion of a liquid to its vapor; it is the reverse of the process of condensation. The rate of vaporization increases as the temperature increases. Vaporization depends on the external factors such as wind speed, humidity, temperature and the surface area of the liquid. When the liquid has strong inter-molecular forces, the evaporation rate becomes slow. Because it holds molecules together in the liquid phase, it needs more energy to escape from the liquid phase to the gas phase. The natural water cycle starts from the vaporization of water from open water surfaces in the presence of sunlight. Vaporization takes place at a faster rate when the external pressure is low. When evaporation takes place, the external environment gets cool down, because heat is absorbed for this process to occur.
Example: For 1 mol (18 g) of liquid water to be completely vaporized, it needs 44.10 kJ (10.54 kcal) of energy.
H2O (l) + 44.10 KJ —> H2O(g)
Note: This is an endothermic reaction. Heat is absorbed for this reaction to occur.
What is Evaporation?
Evaporation is a phase transition, where liquid phase changes to its gas phase at its boiling point. Evaporation is independent of the temperature, but it depends on the atmospheric pressure since the boiling point mainly depends on the atmospheric pressure. Different liquids have different boiling points and it depends on the strength of intermolecular forces. When the vapor pressure of a liquid equals to the external pressure upon the liquid, it starts to boil. This is called evaporation and it depends on the atmospheric pressure. At high altitudes, the atmospheric pressure is less and, therefore, the boiling point is lowered, which means the liquid starts to boil at a low temperature than its normal boiling point. An industrial application of evaporation is the use of steam in boilers as an energy source.
What is the difference between Evaporation and Vaporization?
- Vaporization is the process of changing a liquid to its vapors at a temperature below its boiling point. Evaporation is the process of changing a liquid to its vapors at its boiling point.
- Vaporization can take place at any temperature. Evaporation takes place at the boiling point.
- During the vaporization, temperature of the liquid changes. During the evaporation, temperature is a constant (=boiling point).
- Vaporization is a surface process. It takes place only at the surface of a liquid. Evaporation takes place over the entire mass of the liquid.
- Vaporization is a slow and silent process. Evaporation is a speed and violent process.
- The rate of vaporization depends on the surface area of the liquid, speed of the wind, humidity and the temperature. The rate of evaporation is independent of the surface area of the liquid, wind speed, humidity and the temperature.
Evaporation vs Vaporization Summary
Evaporation and vaporization take place in liquids, changing liquid phase into the gas phase. Evaporation takes place at any temperature, but vaporization occurs only at the boiling point. Evaporation is a surface process and it happens slowly whereas vaporization is a bulk process and it is speedy. Evaporation depends on the external factors including temperature, but vaporization is independent of those external factors. The temperature changes when evaporation takes place and the temperature is constant during the vaporization. Evaporation is the main step in natural water cycle. Both evaporation and vaporization have practical applications.