Evaporation: Definition, Process and Examples

Jul 7, 2022

Evaporation

Imagine you spraying your perfume in the morning before you go to work. You could have felt the wetness of the spray when you did that. It stays like that for a little while. Now, after a few minutes, do you think the wetness is still there? The answer is no. However, the smell would be there and could last for hours depending on the perfume or body spray. So, what happens to the liquid is that it evaporates and is turned into a gas.

The evaporation is mainly due to exposure to the surroundings. Let’s discuss more on evaporation in the following passages of this article.

What is Evaporation?

One can define evaporation as a process that transforms liquid into gas or vapour when exposed to the environment. Simply put, evaporation is the change of water state to its gaseous state. For example, when you use body spray, your body will feel mildly cold. The same thing occurs for acetone and water. It is because the water state changes into its vapour state.

Moreover, the only difference is the feeling of coolness. Due to the higher evaporation rate in acetone compared to perfume or water, the body part that is in contact with liquid will be immediately cooled.

Process of Evaporation

Evaporation is a simple form of vaporisation that takes place on the liquid’s surface. It usually involves the transition of a liquid phase into a gaseous one. Hence, one can say that this process includes a state change of liquid particles. The gas that surrounds the liquid should not contain evaporating substances.

Furthermore, they are capable of transferring energy between each other as the liquid molecules collide. It also depends on how they collide with one another. The particles present in liquid escape and go inside the surrounding air. It then turns fully into gas when a molecule is present close to the surface and consumes essential energy to outperform the vapour pressure.

In addition, the energy obtained from the vapourised liquid will reduce the liquid’s temperature due to the evaporation process. It will further result in a phenomenon called evaporative cooling.

Evaporative cooling

The other name for evaporative cooling is adiabatic cooling. It works based on the principle of evaporation of water. Here, the air will be cooled down to a comfortable temperature. Evaporative cooling is a cooling and ventilation technique that utilises water as its refrigerant.

Moreover, during this process, we can tell that the water has evaporated in an airstream. It then passes from a liquid phase to a gaseous state. To make this transition happen, we need energy. We can extract this energy from the air, which is in the form of heat. Due to that, the air will be cooled down.

The following are some of the ways in which this cooling process is applied:

Direct adiabatic cooling
Indirect adiabatic cooling
Indirect/direct adiabatic cooling

Relationship between Evaporation and Cooling

Let us take a look at how evaporation is capable of causing cooling in the following points:

Evaporation can cause natural cooling. The matter should be able to gain or lose energy in order for it to change its state. When the phase change occurs from liquid to gas, the matter molecules will need to overcome their potential energy with the help of kinetic energy. As a result, the liquid is obliged to take this energy from the environment.
In general, when there is an occurrence of energy transfer, it will result in a rise or fall in the substance’s temperature. However, it all depends on the location where there is a transfer of energy from the substance to the surroundings or in reverse. In addition, there are some exceptions as well to this rule.
Furthermore, there tends to be a rise in the substance’s temperature until it reaches its boiling point during evaporation. During that time, the change of phase will result in a non-observable heat transfer.
The substance’s molecules are capable of absorbing heat energy continuously from the environment. It further cools the surroundings down until their boiling point is reached. After that, the molecules tend to break free from the liquid and transform into vapour. The temperature will not change until the completion of the evaporation process.
The whole liquid is transformed into vapour, and energy requirements for this phase are termed latent heat of vaporisation. The meaning of ‘latent’ is ‘hidden’. It indicates that there will be no change in the thermometer’s temperature reading.

Examples of Evaporation

There are enormous amounts of real-world applications of evaporative cooling. Following are some of them:

As living organisms, we sweat to reduce heat in our bodies. The process of sweating is termed perspiration, and it generally means evaporation. When we do daily tasks, our bodies sweat. It denotes that our bodies release energy in the form of sweat. Sweating is very much helpful in lowering the temperature of our bodies. It will make us feel a little relaxed as well.
It is common to wear cotton clothes and dresses during the summer. It is because cotton is an excellent absorber of liquid and sweat. It enables more sweat to be in contact with the atmosphere, which further enhances the evaporation process. As a result, we might feel a little cooler in cotton clothes compared to polyester or other fabric clothes.
We use earthen pots for storing water and for making it cool. The earthen pot’s pores are capable of providing a huge amount of surface area for increased evaporation, just like cotton clothes.
An ideal application of evaporative cooling can be found in air coolers. We utilise air conditioners and coolers on many different occasions. They are highly effective on hot and dry summer days. The basic working principle of an air cooler involves evaporative cooling. It is very common to have low humidity and high temperature during hot summer days. Due to that, the rate of evaporation can also be found to be higher. The water fetches the air’s energy and transforms into vapour, which makes the air cooler.

Condensation

While learning the concepts and applications of evaporation, knowing the basics of condensation is a must.

We can conclude condensation is the opposite process of evaporation. What happens in condensation is that gas is turned into a liquid. During this process, there will be a loss in heat energy. An ideal example of condensation is the droplets of water on the surface of a cup containing ice-cold coffee.

In simple words, when the vapour of water formed during the evaporation process engages with the cold objects, it loses its energy. It transforms into the water again, in the form of droplets.

Conclusions

In conclusion, evaporation is a much-needed process for our environment because it helps the surroundings. Evaporation determines the occurrence of rain. For example, the places with water resources experience higher rainfall than others. It is because of the evaporation of those water into the atmosphere.

From this blog, we have understood the evaporation meaning, how to define evaporation, and how it can be applied in real-life situations.

Frequently Asked Questions

Q. Mention the steps involved in the water process.

There are four crucial phases in the water cycle. They are:

Evaporation
Condensation
Precipitation
Collection

Q. How does an evaporative cooling system work?

In this system, hot air from the outside is forced to pass through the cooling pads with the help of a motor-driven fan. A water pump is utilised to moisten the cooling pads so that it can deliver the water. The pre-cooled air from the water pump is then blown inside the building.

The resulting air is further cooled between 60% and 90% of the wet-bulb temperature. It depends on the evaporative media’s effectiveness. The air that comes from it has higher humidity levels, and its temperature is between 10 and 15 ℃. Hence, it is not advisable to use direct evaporative cooling in residential buildings due to safety concerns.

Q. What is the importance of evaporative cooling?

Evaporative cooling is an indirect/direct system. It is very sustainable. It consists of an energy-efficient cooling technique capable of providing a comfortable and survivable climate for various business centres like distribution units, production facilities, assembly units and office buildings.

Furthermore, this evaporative cooling process utilises 10% of the energy required for mechanical cooling. However, it can deliver almost the same temperature as traditional mechanical cooling systems.