Evaporation

Evaporation occurs when a liquid turns into a gas. Have you ever noticed that when a glass is left on the counter, the water begins to evaporate? It’s evaporation, not thirsty fairies dwelling in your kitchen. Evaporation is the process by which molecules undergo a spontaneous transition from the liquid phase to the gas phase. Evaporation is the opposite of condensation.

A type of vaporization called evaporation involves the transfer of liquid particles into the gaseous phase and typically takes place on the surface of liquids. As a result, it is stated that this process involves a change in the matter state of liquids.

What is Evaporation?

Evaporation is a process where the liquid state of matter is converted into a gaseous state of matter in the presence of heat. 

Many people get confused between evaporation and boiling, as in boiling, liquid also changes to a gaseous state. But, there is a difference. The very first is boiling of liquid happens at a particular temperature, while evaporation can happen at any temperature below the boiling point. Also, boiling is a bulk phenomenon, whereas evaporation is a surface phenomenon, which means evaporation can happen only at the surface of the liquid. 

During evaporation, the molecule having higher kinetic energy only dissipated from the topmost layer of the liquid. There is also one unique property of evaporation that causes a cooling effect. The earthen pot was used to store cool water in summer as the water got oozed out from tiny pores of the pot causing evaporation and leading to the cooldown of the water inside the pot. Desert cooler also works on the principle of evaporation.

For evaporation to occur, molecules in a liquid must be near the surface, must be moving away from the body of the liquid, and must have enough kinetic energy to escape the interface. When molecules do escape, the average kinetic energy of the remaining molecules is lowered. This lowers the temperature of the liquid and is the basis for the phenomenon of evaporative cooling.

Evaporation depends on some factors too, like temperature, the surface area of the liquid, wind speed, and humidity. We will discuss this in detail in this article.

Examples of Evaporation

There are many examples of evaporation but here we are discussing only a few of them:

• Drying of clothes in sun: We all dried up our clothes in the sun, the wet clothes get dries up because of evaporation where the water turns into water vapor.

• Drying of water bodies: We have seen in summer water in the ponds and lake get decrease or sometimes dried up due to evaporation.

• Water cycle: This is a very good example of evaporation, in the above two we discussed how evaporation turns water into water vapor. This water vapor further goes to the sky and gets condensed to form a cloud, and later it got precipitated. So, evaporation is significant to regulate the water cycle.

• Salt formation: Naturally or industrially salt forms due to evaporation where the water gets evaporated to leave us salt.

• Drying of a Mopped Floor

• Working in the desert cooler in summer.

Process of Evaporation

A liquid evaporates when it is heated. This implies that the molecules in the liquid must acquire kinetic energy. A liquid’s molecules expand out and vibrate more quickly as it acquires kinetic energy. The liquid turns into a gas as a result, changing its state of matter.

Water is a common substance where evaporation occurs. Water changes from a liquid to a gas when energy or heat is applied because the bonds keeping the molecules together start to weaken. The boiling point of water, which is 212 degrees Fahrenheit or 100 degrees Celsius, is the point at which it transforms from a liquid to a gas.

Factor affecting Evaporation

Evaporation eases our life in many ways, and even it is contributing to the water cycle too. But evaporation is dependent on some factors which will be going to control the rate of evaporation. One more thing to note evaporation is a slow process but some external factors increase or slow down the rate of evaporation. Let’s discuss all these factors of evaporation:

Temperature

The very first factor is temperature since we know evaporation can happen at any temperature before the boiling point, but the temperature has a role in evaporation too. It will determine the rate of evaporation, the more the temperature more is the rate of evaporation. Now the question is how? We all know the temperature will increase the kinetic energy, as the energy used to break intermolecular forces that bind the liquid molecule. So, when we apply more temperatures the molecule rapidly breaks its intermolecular forces and get evaporated. 

This implies,

Temperature ∝ Evaporation

For Example, we all have seen in the hot summer clothes get quickly dried up than on normal days. This is due to the Temperature factor.

Must Check

• Unit of Temperature
• Relationship Between the Celsius and Kelvin Scale of Temperature
• Effect of Change of Temperature

Surface Area of the Liquid

Earlier we discussed that evaporation is a surface phenomenon, and the surface plays a role in the rate of evaporation. The more a surface area more will be the rate of evaporation. So, if more surface area will be there then more liquid molecules will present on the surface, meaning more molecules break their intermolecular bonds which will increase the rate of evaporation. So we can write it as;

Surface area of liquid ∝ Evaporation

For example, the same amount of water gets evaporated more quickly in a plate than the water in a shallow cup, this is because the plate offers a greater surface area for the liquid than the shallow cup.

Humidity

Humidity refers to the amount of wetness or water vapor in the air. The more water vapor in the air we will say more humidity. With more humidity, the rate of evaporation gets decreased.

Humidity ∝ 1/Evaporation

For example, in the rainy season when our surrounding is more humid than it is very difficult to dry up our clothes.

Wind Speed

Wind speed is directly proportional to evaporation means with the increase in wind speed there would be an increase in the rate of evaporation.

Wind Speed ∝ Evaporation

For example, on a windy day, clothes get quickly dried up than on normal days. This is because the wind decreased the humidity which will increase the rate of evaporation.

Also Read

• Effects of Relative Humidity and Wind Speed

Difference between Evaporation and Boiling

Below is the major differences between Evaporation and Boiling.

Evaporation	Boiling
Evaporation is a natural process in which the liquid changes into gaseous form due to an increase in either temperature or pressure or both.	Boiling is simply the vaporization, which turns liquid into gas by continuous heating.
Evaporation occurs only on the surface of the liquid.	However, boiling occurs throughout the large mass of the substance.
In case of the evaporation, the temperature does not cross the Boiling point of the liquid.	However, in boiling, the process occurs only at the boiling point of the liquid.
Hence, it is a Slow Process.	Hence, this is a rapid process.
Rate of evaporation increases with an increase in the open surface area of the liquid.	Rate of boiling is independent of the open surface area of the liquid.

Difference between Evaporation and Vaporization

The difference between evaporation and vaporization is tabulated below:

Evaporation	Vaporization
Surface phenomenon	Bulk phenomenon
Occurs at any temperature	Occurs at specific temperature
Occurs only at the surface of a liquid	Occurs throughout the bulk of the liquid
Process is slower	Process is relatively faster
Not easily visible	Visible during boiling
Heat required for evaporation is less	Heat required for vaporization is more
Examples: Drying clothes, puddles	Examples: Boiling water, steam formation

Must Read

• Evaporation Causes Cooling 
• Separation by Evaporation
• Crystallization

Evaporation – FAQs

What is the difference between Evaporation and Vaporization?

The phase change of a substance or element that takes place during the boiling or sublimation process is known as vaporisation. Simply said, evaporation is a form of vaporization that primarily takes place when the temperature is below the boiling point. A substance’s state can shift from a solid or liquid to a gas by vaporization.

What are the Factors affecting Evaporation?

Following are some factors that determine the rate of evaporation:

• Surface area of the liquid: More is a surface area more will be the rate of evaporation. Thus, the Surface area of liquid ∝ Evaporation.
• Humidity: With more humidity, the rate of evaporation gets decrease, means Humidity ∝ 1/Evaporation.
• Wind Speed: Wind speed is directly proportional to evaporation means with the increase of wind speed there would be an increase in the rate of evaporation

How does Evaporation differ from Boiling?

The process of evaporation is very much different from boiling in many ways. Evaporation is a natural process in which the liquid changes into gaseous form due to an increase in either temperature or pressure or both. However, boiling is not a natural process, it is simply the vaporization, which turns liquid into gas by continuous heating. 

How does evaporation occur in water cycle?

When sunlight warms the water’s surface, evaporation takes place as part of the water cycle. The sun’s heat causes the water molecules to travel ever-faster until they are able to escape as a gas. A water vapour molecule spends roughly 10 days in the atmosphere after it has evaporated.

What is Evaporation? Give an example.

Evaporation is a process where the liquid state of matter converted into a gaseous state of matter in the presence of heat. For example, We all dried up our clothes in the sun, the wet clothes get dries up because of evaporation where the water turns into water vapor.

Why it is very difficult to dry up clothes in the humid season?

Since we know that humidity refers to the amount of wetness or water vapour in the air. The more water vapour in the air we will say more is humidity. With more humidity the rate of evaporation gets decrease Thus, it will become very hard to dry up the clothes in the humid season.

Write four examples of evaporation.

Examples of evaporation are as follows:

• Drying of water bodies
• Water cycle
• Salt formation
• Drying of a Mopped Floor

How increase in temperature affects the rate of evaporation?

The more the temperature more is the rate of evaporation. This is because temperature will increase the kinetic energy, and the energy used to break intermolecular forces that bind the liquid molecule. So, when we apply more temperature the molecule rapidly break their intermolecular forces and get evaporated. 

What is opposite of evaporation?

Condensation is the opposite of evaporation. A type of vaporization called evaporation involves the transfer of liquid particles into the gaseous phase and typically takes place on the surface of liquids. As a result, it is stated that this process involves a change in the matter state of liquids.