Tag: Evaporation

Introduction

Evaporation is the transition from the liquid to the vapour phase that takes place at pressures and temperatures below the boiling point (a condition of a substance just below its critical temperature). Evaporation occurs only when a substance’s relative vapour pressure is less than its equilibrium state vapour pressure. However, rather than a phase shift from liquid to gaseous, boiling is the formation of vapour as vapour bubbles immediately below the surface of the liquid. Rather than the literal conversion of the substance to gas, the term “vaporisation” has been used informally or hyperbolically to represent the actual physical disintegration of an object when subjected to high temperature or explosive force.

What is Vaporization?

Vaporization can be thought of as the transformation from a liquid to a gaseous state. When the temperature is raised, the kinetic potential of the molecules also increases. The force of attraction between molecules weakens as their kinetic energy increases. Because of this, they become airborne and spread over the area. This process requires the use of thermal energy.

Types of Vaporization

There are three types of vaporisation:

Evaporation

If you lower the temperature of a liquid below its critical point, you can cause a phase transition is known as evaporation to occur, in which the liquid changes into a gas.

The top is the primary site of evaporation. To begin evaporating, a substance must have a partial vapour pressure less than its equilibrium. So, for instance, if you continuously sucked the air out of a solution, you’d eventually be left with just a cryogenic liquid.

Boiling

Boiling is not a phase transition from the liquid state to the gaseous state but rather the creation of vapour below the surface of the liquid as vapour bubbles. Boiling occurs when the chemical’s equilibrium vapour pressure is higher than or equal to the ambient pressure. The boiling point of a substance is the temperature at which boiling occurs. The boiling point is affected by atmospheric pressure.

Sublimation

We know that ice melts into a liquid, and subsequently, the liquid evaporates into steam. However, there is a process through which matter can transition from its solid state into its vapour state, bypassing the liquid state entirely. Sublimation is the direct transformation of a solid into a gas.

Factors affecting the Rate of Vaporization

The rate of vaporization is affected by several factors, such as:

• The concentration of minerals in the solution.
• The amount of a substance that evaporates into the air.
• Due to the increased interactions between the molecules, more energy is needed to escape the liquid state.
• The point at which the liquid or gas begins to evaporate is called the vaporisation temperature. 
• Reduced surface tension allows molecules to escape the surface faster, leading to increased evaporation rates.
• Evaporation rate is proportional to the surface kinetic potential of the molecules, which increases with temperature.
• Width of the Surface: Evaporation rates are proportional to the number of particles on the surface, so a bigger surface area means higher evaporation.
• If “clean” air (wind that is not yet laden with a drug or even other chemicals) is constantly passing across the substance, allowing for rapid evaporation, the amount of the chemical in the atmosphere is less likely to rise over time.
• Humidity refers to the amount of water vapour in the air.
• Because warmer air can hold more water vapour than cooler air, the evaporation rate will increase if the wind speed and humidity stay constant.

Examples of Vaporization in Our Daily Life 

• Clothing that has been soaking wet can be dried through evaporation.
• This occurs when moisture in damp garments is evaporated when exposed to the sun’s thermal radiation.
• Separating the components of a mixture using this method is a common practice in many industrial processes.
• Using a vaporisation process, salt is produced from seawater in an industrial setting.
• Evaporation is used to remove salt from saltwater to produce table salt.

 

Frequently Asked Questions

1. What is the significance of the latent heat of vaporisation?

Ans: During a change of condition, heat energy is effectively hidden.

Latent heat, a form of hidden power used only during phase transitions, is also called the latent heat of vaporisation when it happens during the phase transition from liquid to gas.

2. What is critical temperature?

Ans. It is possible to define the critical temperature of a substance as the greatest temperature at which the substance can be in a liquid state.

No amount of pressure can cause a gas to turn into a liquid after it has reached a temperature over its critical temperature.

3. Does latent heat of vaporisation depend on the mass of the substance?

Ans. No, the latent heat of vaporisation does not depend on the mass of the substance. It has a fixed value at a given temperature and is not affected by the substance’s mass or volume. 

Introduction

A “mixture” is a combination of two or more substances, such as water and sand, salt and water, or a solution of two solutes, for example. These mixtures are not chemically linked. Hand-picking, winnowing, filtration, distillation, and other techniques are used to separate them. The mixture can be solid in solid, liquid in liquid, gas in gas, and so on. Seawater is also a salt-water mixture. The “evaporation method” is used to separate salt from seawater. Different techniques are used to separate different types of mixtures.

Methods of Separating Mixtures:

Depending on the type of mixture, there are various methods for separating it. In 1840, some prospectors used water to separate gold from a mud mixture; the mud containing gold was filled with water in a pan.

After a while, the pan was twisted to remove the dissolved material, and gold settled in the pan due to its weight. Panning is the process of separating gold from water.

Substances in our environment exist as mixtures, of which there are two types: “homogenous” and “heterogeneous” mixtures.

Different techniques are used to separate them.

Hand-picking: 

The hand-picking method is used to separate the mixtures that are less in quantity and the size of the particle is big. It is usually used to separate stones from grains, rice pulses, etc at home and groceries shops. In this type both the components are in solid form, these are big enough to separate them by hand.

Threshing:

This method is widely used to separate grains from twigs. Farmers use this method to separate hard wheat, rice, pulses, and other grains from their stalks. When food grains reach maturity, the farmer harvests and dry them in the field.

Winnowing:

This method is used to separate the husk from grain or pulses with the help of “ wind” that’s why it is named “winnowing”. 

• In this method, the grains separated by the threshing method contains small twigs, and a husk that is quite thin and light in weight. 
• The grains containing husk are taken in a winnowing basket. The farmer stands at a particular height, taking that basket in the direction of the wind. 
• The farmer falls the grains, the husk, and the twigs get separated by the flow of wind and the grains get cleaned.

Evaporation

1. To separate the mixture into liquid form, “the evaporation technique” is used. The volatile material evaporates, leaving behind a non-volatile solid in the container.
2. The mixture is heated in this method until the liquid portion of the mixture evaporates.
3. The mixture’s solid component is left in the container.
4. This method separates salt from seawater.

Distillation

The “distillation method” is used to separate two or more mixed liquids.

1. A “distillation apparatus” in this method is a plant that contains a flask, a thermometer, a condenser, and a collecting flask (distillate).
2. The mixture is heated to a specific temperature in the distillation flask.
3. The liquid begins to boil and turns into vapour.
4. This vapour is collected in a “distillate” after being condensed in a condenser.

Filtration 

It is a common technique for separating liquids from insoluble solids.

1. The “filter paper” is used in the filtration process to separate liquid from the mixture that is large enough to become trapped in the porous material.
2. To separate water from a sand and water mixture.
3. Heavy impurities are settled down during the sedimentation process.
4. The first liquid, which is above, is then slowly separated from the flask.
5. This method is used to separate mud and water mixtures.

Summary

The elements in the environment are found in combination with other elements. These are both homogenous and heterogeneous mixtures. The mixture can exist as a liquid, solid, or gas. The two materials are not chemically bonded. Depending on the type of mixture, different methods are used to separate it.

Frequently Asked Questions

1. How are the essential oils extracted from the flowers?

Ans. Steam distillation is used to separate the essential oils. The liquid is converted into steam in this process, and the steam vaporises the material with it before being condensed and separated in a retort.

2. Which mixture is separated using cryogenic distillation?

Ans. This method is used to separate the acid gas mixture from the gaseous mixture, LPG, and is similar to removing CO2 from LPG.

3. How are fatty acids, resins, and wax separated from the mixture?

Ans. Drugs, esters, fatty acids, tocopherols, resins, and wax are separated from mixtures using short-path distillation.