Vaporisation

The mechanism through which the state of a liquid converts into the condition of a vapour is known as vaporisation. As the temperature rises, the kinetic energy of the molecules rises as well. Because of the increase in kinetic energy, the force of attraction between the molecules decreases. As a result, they escape into the surrounding area as vapours. This method necessitates the use of heat energy.

Factors that Influence Vaporisation Rate

• The amount of an evaporating substance in the air.
• Air Flow Rate – This is linked to the concentration points mentioned above. If ‘fresh’ air (air that hasn’t already been contaminated by a chemical or other substances) is repeatedly blown over the substance, the concentration of the substance in the air is less likely to rise with time, allowing for rapid evaporation. The effect of increasing the velocity of flow on the boundary layer at the evaporation surface reduces the distance of diffusion in the stagnant layer.
• The amount of minerals that have been dissolved in the liquid.
• Intermolecular Forces – The greater the forces holding the molecules together in the liquid state, the more energy is required to escape. The vaporisation enthalpy describes this.
• Evaporation occurs more quickly when there is less effort on the surface to keep the molecules from launching themselves.
• Surface Area – A material with a larger surface area can theoretically evaporate faster since there are more surface molecules per unit of volume that can escape.
• The Temperature of the Substance- The higher the temperature of the substance, the higher the surface kinetic energy of the molecules and the faster they evaporate.

Types of Vaporisation

There are two types of vaporisation: evaporation and boiling. Boiling is a bulk phenomenon, whereas evaporation is a surface phenomenon.

Boiling

Boiling is the creation of vapour below the liquid surface as bubbles of vapour, not a phase transition from the liquid to the gas phase. When the equilibrium vapour pressure of a substance is greater than or equal to the ambient pressure, it boils. The boiling temperature, often known as the boiling point, is the temperature at which water starts to boil. The boiling point varies depending on the pressure in the surroundings.

Applications

• Most forms of refrigeration and some types of air conditioning work by compressing a gas until it becomes liquid and then allowing it to boil. This absorbs heat from the environment in order to cool the refrigerator or freezer, as well as the air entering the home. Typical liquids include propane, ammonia, carbon dioxide, and nitrogen.
• To Make Potable Water – The oldest and most efficient method of disinfecting water is to bring it to a boil at 100 degrees Celsius (212 degrees Fahrenheit), because it has no taste, is effective even if pollutants or particles are present, and is a one-step process that removes the majority of microbes that cause intestinal disease.
• Boiling is a culinary technique that involves heating food in boiling water or other water-based liquids such as stock or milk.

Vaporisation Examples

• Salt is extracted from seawater using a vaporisation method in the industrial sector.
• Wet garments can be dried using the vaporisation technique.
• In many production processes, the approach is used to isolate the components of a mixture.

Did You Know?

Sublimation is an endothermic process that takes place at temperatures and pressures below a substance’s triple point, which is the lowest pressure at which the substance can exist as a liquid. The reverse sublimation process involves deposition or sublimation, in which a substance goes directly from a gas to a solid state. Sublimation has also been used as a catch-all phrase to describe a transition from solid to gas followed by a transition back to solid (deposition).

High Vaporisation Heat

The heat required to transform 1 gramme of liquid into the gaseous state is known as the high heat of vaporisation. The hydrogen bonds in liquid water begin to break as the temperature rises. The highest known heat of vaporisation is that of water. When heat is applied to water, the molecules begin to disintegrate and evaporate. Water has the highest heat of vaporisation because the surface molecules cool and more kinetic energy is required to evaporate it.

When a liquid in a closed container is heated, the liquid that is being converted to a gaseous state is impossible to escape through evaporation. This process continues until the liquid state has the same number of molecules as the solid state. The vapour is said to be saturated vapour at this point, and the pressure associated with it is said to be saturated vapour pressure.

Conclusion

Vaporisation facilitates the transition from a liquid to a gaseous state. Boiling and evaporation are the two kinds of vaporisation. The vaporisation graph declines with temperature until it reaches a critical point known as Critical temperature. Condensation is the reversal of the vaporisation process. Nils Wallerius was the first to use scientific methods to investigate the evaporation and vaporisation of liquids.