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Difference between evaporation and boiling
Difference between evaporation and boiling is frequently asked question in interview of a fresh or resent graduated Chemical engineering students. as a fresh Chemical engineer you have to know some basic concepts related to chemical engineering. You must have full knowledge regarding some basic concepts like vapor pressure , boiling point , evaporation , pump head calculation , pump NPSH calculation , heat transfer and mass transfer operations and unit like of pressure and temperature and all types of unit.
This article contains what is boiling , boiling point, Difference between evaporation and boiling , what is evaporation .
Boiling
Boiling is nothing but a process in which we can heat a liquid or liquid get heated due to atmosphere converted in to vapour phase. In simple boiling is a phase change process in which a liquid or fluid or material is converted in to vapour phase . Boiling is happen at its boiling point temperature . Boiling point temperature of every material is different. Some material have same boiling temperature too. Boiling point of any liquid or material is dependent on its type of binding and atmospheric condition. When we mix two mixture like methanol and water , boiling point of mixture is almost 80 degree Celsius (Difference between evaporation and boiling ).
As we know that boiling point of water is 100 degree Celsius and boiling point of methanol is 64 degree Celsius. But boiling point of mixture of methanol and water is almost 80 degree Celsius.
Boiling of any liquid or Component is start when it’s vapour pressure is equal to atmospheric pressure, like boiling point of water is 100 degree Celsius at atmospheric pressure . If we change the pressure boiling point also change. Like if we need to boil the water below 100 degree Celsius we can reduce the pressure below the atmospheric pressure. Roult’s law is useful to calculate boiling point at different pressure. This relationship give a value of change in boiling temperature with respect to change in pressure.
What is boiling point ?
It is temperature when liquid start to boil at a certain surrounding pressure it may be atmospheric or any other pressure.
Boiling point is nothing but a certain temperature of any liquid at equilibrium condition , i.e. it is temperature when po pressure exerted by surrounding is equal to the vapour pressure of of liquid. In short boiling happen when liquid vapor pressure will same as it’s surrounding pressure. Must read .
In normal conditions , boiling point is nothing but temperature of liquid when it start to boil or temperature of liquid when it’s vapour pressure is equal to atmospheric pressure .
Evaporation
Evaporation is a nothing but a process in which liquid go to vapour phase but without boiling. This happen may be due to external heating or natural heating.
Difference between evaporation and boiling
Now we will start with our main or basic question what is Difference between evaporation and boiling ?.
Boiling is fast process as compared to the evaporation or evaporation is slow process as compared to boiling. Boiling happen at a certain temperature only but evaporation does not required a certain temperature . Boiling occurrence is in entire mass or volume of liquid and evaporation occurrence is at only upper surface of liquid.
difference between boiling point and evaporation in chemical engineering
boiling point and evaporation:
| Question | Answer |
|---|---|
| What is the boiling point of a substance? | The boiling point of a substance is the temperature at which its vapor pressure equals the atmospheric pressure, causing the liquid to change into a gas. |
| How does atmospheric pressure affect the boiling point of a substance? | Higher atmospheric pressure increases the boiling point, while lower atmospheric pressure decreases it. |
| How does altitude affect the boiling point of water? | At higher altitudes where atmospheric pressure is lower, the boiling point of water decreases. |
| Can the boiling point of a substance change under different conditions? | Yes, the boiling point of a substance can vary depending on factors such as pressure, altitude, and the presence of impurities or dissolved substances. |
| What is evaporation? | Evaporation is the process by which a liquid changes into a gas or vapor state at a temperature below its boiling point. |
| How is evaporation different from boiling? | Evaporation occurs at the liquid’s surface and can happen at any temperature, while boiling occurs throughout the bulk of the liquid at its boiling point. |
| What factors influence the rate of evaporation? | Factors such as temperature, surface area, humidity, air movement, and vapor pressure affect the rate of evaporation. |
| How does evaporation contribute to cooling? | Evaporation has a cooling effect as it reduces the average kinetic energy and temperature of the remaining liquid. |
| Can evaporation occur in a closed container? | Yes, evaporation can occur in a closed container until the vapor pressure of the substance reaches equilibrium. |
| How is the concept of boiling point and evaporation utilized in various industries and applications? | Boiling point and evaporation are applied in industries such as food processing, distillation, chemical manufacturing, and HVAC systems |
QNA on boiling point and evaporation
What is the boiling point of a substance?
The boiling point of a substance is the temperature at which its vapor pressure equals the atmospheric pressure, causing the liquid to change into a gas throughout the bulk of the liquid.
How does atmospheric pressure affect the boiling point of a substance?
Higher atmospheric pressure increases the boiling point of a substance, while lower atmospheric pressure decreases it. This relationship is explained by the fact that higher pressure requires more energy to overcome, resulting in a higher temperature needed to reach the vapor pressure threshold.
How does altitude affect the boiling point of water?
At higher altitudes where atmospheric pressure is lower, the boiling point of water decreases. This is why it takes less time to boil water at higher altitudes compared to sea level.
Can the boiling point of a substance change under different conditions?
Yes, the boiling point of a substance can vary depending on factors such as pressure, altitude, and the presence of impurities or dissolved substances in the liquid ( Difference between evaporation and boiling ).
What is an evaporation?
Evaporation is the process by which a liquid changes into a gas or vapor state at a temperature below its boiling point. It occurs at the liquid’s surface, as the more energetic molecules escape into the surrounding atmosphere (Difference between evaporation and boiling ).
How is evaporation different from boiling?
Evaporation occurs at the liquid’s surface and can happen at any temperature, whereas boiling occurs throughout the bulk of the liquid and requires the liquid to reach its boiling point.
What factors influence the rate of evaporation?
Factors such as temperature, surface area, humidity, air movement, and the vapor pressure of the liquid affect the rate of evaporation. Higher temperatures, larger surface areas, lower humidity, and increased air movement generally accelerate evaporation (Difference between evaporation and boiling ).
How does evaporation contribute to cooling?
Evaporation has a cooling effect because the more energetic molecules escape as a gas, which reduces the average kinetic energy and temperature of the remaining liquid. This cooling effect can be observed, for example, when sweat evaporates from the skin, creating a cooling sensation.
Can evaporation occur in a closed container?
Yes, evaporation can occur in a closed container until the vapor pressure of the evaporated substance reaches equilibrium. At this point, condensation may start to occur as well.
How is the concept of boiling point and evaporation utilized in various industries and applications?
The understanding of boiling point and evaporation is applied in various industries, including food and beverage processing, distillation processes, chemical manufacturing, air conditioning and refrigeration systems, and many other fields where precise temperature control and phase changes are essential ( Difference between evaporation and boiling ).
Conclusion
From above explanation it is clear that boiling occur in hole volume of liquid while evaporation occur at liquid surface only also boiling is very fast process than evaporation .
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