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What is Vaporization?

Vaporization is the stage of an element or compound turning to a gaseous state from the liquid state. There are two types of vaporization and they are evaporation and boiling.

Evaporation is the surface process wherein sprinkles of liquid spread on the ground turn to steam when the surface is hot. However, boiling is a bulk phenomenon, meaning, this process occurs when the vessel filled with water is kept on high flame and the liquid turns to steam.

In this article, we will discuss how vaporization occurs, types of vaporization, in detail.

Vaporization

One thing to note is that heat is required to convert solid or liquid into a gaseous (steam) state.

When a system captures hear from its surroundings, there is a temperature rise. So, when there is a temperature rise, the atoms or molecules of a liquid or solid that are held together by cohesive forces, turn to adhesive forces, which in turn,  separate the atoms or molecules to form the vapor; therefore, the heat of vaporization is a direct measure of these cohesive forces.

It means more is the cohesive force between molecules, the more is heat required to vaporize the solid or liquified elements.

Now, let’s understand the types of vaporization:

Types of Vaporization

There are three types of vaporization, and these are as follows:

  • Evaporation

  • Boiling

  • Sublimation

Evaporation

It is a phase transition from the liquid to the vapor phase, i.e., a state of substance/material below the critical temperature occurs. 

Evaporation occurs at temperatures lower than the boiling temperature at a given pressure, it always occurs on the surface. That means the water suddenly escapes into the atmosphere (no formation of bubbles or something).

Drying your clothes on the roof is an example of evaporation.

Point to Note:

Evaporation occurs only when the partial/incomplete pressure of vapor of a substance/material is lower than the equilibrium vapor pressure. 

Another example, due to continuously decreasing pressures, vapor pumped out of a solution eventually leaves behind a cryogenic (cancer-causing) liquid at temperatures below the boiling temperature at a given pressure. 

Boiling

Boiling is similar to evaporation. It is also known as the phase transition from the liquid to the gas phase, but boiling is the formation of vapor as bubbles of high-temperature water below the surface of the liquid just like we keep the water jar on a high flame, it turns to bubbles and then the steam escapes into the atmosphere. 

Point to Note:

Boiling occurs only when the equilibrium vapor pressure of the substance is greater than or equal to the environmental/atmospheric pressure

Hence, the temperature at which boiling occurs is the boiling temperature or boiling point. The boiling point varies with the pressure of the environment or the atmospheric pressure.

Sublimation

We all know that firstly ice converts to liquid and then this liquid turns into steam; however, there is a process that directly converts solid into gaseous form without turning to the liquid phase. So, the direct transition of solid into the gaseous state is sublimation.

Uses of Vaporization

The term vaporization was being used in colloquia/hyperbolic manner to allude to the physical destruction of an object/element that is exposed to intense heat or explosive force, where the object of large mass is split into small pieces rather than converting into gaseous form. 

The example includes the usage of the "vaporization" in 1952 the Ivy Mike thermonuclear test that was performed in the uninhabited Marshall Island of Elugelab.

Vaporization or Ablation

Vaporization occurs when a laser heats the material above or equivalent to its boiling point. The high-power densities generated by short-pulsed lasers let the vaporization occur with minimum thermal damage to the surrounding material. This, in turn, allows fine features to be formed without the production of any notable heat-affected zone or recast layer.

Point to Note:

In the process of laser drilling, the term ablation is usually used to indicate a vaporization-dominated process. Though, the term is not well-defined; however, this term applies to processes in which there is also significant melting.

Saturated Vapour

When evaporation occurs in a closed container, it proceeds until all the molecules inside the liquid escape. At this juncture, a vapor is said to be saturated. The pressure of the saturated vapor is expressed in mmHg; this pressure is also called the saturated vapor pressure.

Since the molecular pressure and the kinetic energy of each molecule inside the container is high because of the high temperature; therefore, more molecules escape the surface, and the saturated vapor pressure also increases.

The below diagram shows how the saturation occurs:

[Image will be Uploaded Soon]

Vapor Lock

A Vapor lock is a partial/complete interruption/disruption of the fuel flow in an internal-combustion engine that is caused by the formation of vapor or bubbles of gas in the fuel-feeding system. 

Vapor lock disrupts the operation of the fuel pump, leading to the loss of feed pressure to the fuel injection system, resulting in transient loss of power or complete stalling/stoppage.

FAQs (Frequently Asked Questions)

Q1: Define the Enthalpy of Vaporization.

Ans: The enthalpy of vaporization, i.e., symbolized as ∆Hvap, is known as the latent heat of vaporization/heat of evaporation. It is the amount of energy or enthalpy added to a liquid substance to transform a given quantity of that substance into a gas phase. 

The vaporization of a liquid is closely associated with a significant increase in the distance between molecules and a reduction in their interactions. The average molar enthalpy of vaporization or ΔHvap for nonpolar compounds is given by the following empirical Hildebrand's rule:

 ΔHvap ≈ 11 R Tvap 

Where Tvap is the temperature of vaporization.

The enthalpy of vaporization is generally considered for the normal boiling temperature of the substance whose value is usually corrected to 298 K. 

Q2: Describe Electrochemical Vaporization.

Ans: It is a type of vaporization in which a small amount of material, i.e., 5-100 L of the substance is deposited in the electrically conductive vaporization cell. A small magnitude of electric current is supplied to the cell. 

This causes resistive heating to occur and drying of the sample. After this, a high current is passed for a short time, i.e, around 5 seconds to completely vaporize the sample.

Q3: How does Vapor Lock occur?

Ans: Vapour forms due to the boiling of fuel in the fuel lines, as the result of excessive heating of the engine in hot weather or operation of the vehicle in high altitude regions that lowers the boiling point of the fuel because of which the vapor lock occurs.

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