Difference Between Evaporation and Boiling

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Have you tried cooking Maggi at the top of a mountain? Not yet? Well cooking Maggi at the top of the mountain will not only test your cooking skills but Chemistry knowledge as well. So, before you reach the top of the mountain and test your cooking skills, let us tell you the Chemistry behind it to make your experience better.

Water boils at 100 at sea level while at higher altitudes such as at the top of a mountain, water starts boiling at lower temperature. When we try to cook Maggi at the top of a mountain, water boils at lower temperature and evaporates quickly. Due to this Maggi remains half cooked and we need to add more water to cook it nicely. Thus, it takes more time to cook Maggi at the top of a mountain.

In this article, first we will discuss evaporation and boiling separately at a length and then the difference between them to understand the concept clearly.

What is Boiling?

Boiling is the rapid vaporization of the liquid when it is heated to its boiling point. For example, when we heat water up to 100 at sea level, it starts boiling and converts into vapor. Boiling water is used to kill microbes present in it and to make it soft. It is used in several cooking methods as well.

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In the boiling process, vapor pressure of the liquid can overcome atmospheric pressure. That’s why bubbles can form and rise upwards in boiling.

What is Boiling Point?

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. Boiling point of a substance can vary according to the surrounding environmental pressure. A liquid at higher pressure has a higher boiling point and at lower pressure has a lower boiling point for example, at sea level water boils at 100 while at higher altitudes where the atmospheric pressure is lower water boils at lower temperature than 100

Factors Affecting Boiling Point

Following factors affect the boiling point –

• Atmospheric Pressure – Boiling point of a substance changes according to the pressure of its surroundings. At higher atmospheric pressure more energy is required to break the bonds between particles which results in increase of boiling point. Thus, higher pressure elevates the boiling point while lower pressure depresses the boiling point.

• Impurities – Boiling point of a compound is used as a reference property of its pure form. For example, pure water boils at 100 while water with various other substances or impure water boils at higher temperature. Thus, impurities in a pure substance elevates the boiling point.

What is Evaporation?

Take a beaker and put water in it. Now put this beaker on the flame and keep heating it. After some time, you will notice that water starts boiling and changes into vapor. This phenomenon is called vaporization. Now have you noticed that if a glass of water falls on the floor and no one wipes it but still after some time it dries. In the same way wet clothes dry up after some time. Do you know how? Well as we know that particles of matter are always moving and are never at rest it means they possess different amounts of kinetic energy at different temperatures. In the case of liquid as well a small fraction of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction of other particles and gets converted into vapors. This phenomenon of change of a liquid into vapors at any temperature below its boiling point is called evaporation.

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Factors Affecting Evaporation

Following factors affect rate of evaporation –

• Surface Area – Evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation also increases. For example, we spread clothes out to dry them faster. Relation between rate of evaporation and surface area can be written as –

Rate of Evaporation $\propto$ Surface area

• Temperature – Rate of evaporation increases at higher temperatures. As with increase of temperature, a greater number of particles get enough kinetic energy to go into the vapor state. For example, wet clothes dry quickly under sunlight. Relation between rate of evaporation and temperature can be written as –

Rate of Evaporation $\propto$ Temperature

• Humidity – Humidity is the amount of water vapor present in air. Air cannot hold more than a definite amount of water vapor at a given temperature. If the amount of water in air is already high or maximum, the rate of evaporation decreases. Relation between rate of evaporation and surface area can be written as –

Rate of Evaporation $\propto \frac{1}{{Humidity}}$

• Wind Speed – With increase in wind speed, the particles of water vapor move away with the wind, decreasing the amount of water vapor in the surrounding. Thus, increase in wind speed increases the rate of evaporation as well. For example, clothes dry faster on a windy day. Relation between rate of evaporation and surface area can be written as –

Rate of Evaporation $\propto$ Wind Speed

Differences Between Evaporation and Boiling

 S.No. Evaporation Boiling 1. It is the process of changing liquid into vapor. It is a process in which vapor pressure of the liquid becomes equal to its surrounding pressure and liquid changes into vapor. 2. It can take place at any temperature. It does not have a specific temperature. It occurs at boiling point. The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. 3. It takes place below the boiling point temperature. It takes place above the temperature at which evaporation takes place. 4. It is a surface phenomenon. It means it takes place on the surface of the liquid. It takes place from the whole liquid mass. 5. In evaporation, liquid does not form bubbles. In this process liquid forms bubbles which rise upwards. 6. It is a slow process. It is a rapid process. 7. Generally, an external heat supply is not required. Molecules collide with each other and that energy is used to escape to the vapor state. It requires a high amount of heat.

This ends our coverage on Difference between evaporation and boiling point. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to answer questions related to this topic. If you are looking for solutions to NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.