Methods of Separation - Definition, Mixtures, FAQs

Methods of Separation - Definition, Mixtures, FAQs

Team Careers360Updated on 02 Jul 2025, 04:49 PM IST

What is Separation?

A separation is a process where the compounds of interest are removed from the other compound in a sample that may or may not react similarly and interfere with a quantitative determination. The process of separation is done to remove unrequired component(s) or obtain desired component(s) from a mixture. In other words, done for separating components of a mixture. Separation techniques are used in the preparation of pure compounds and almost every chemical substance we see around us. A common example is separation of sand and water. A mixture of sand and water can be separated by filtration method.

Filtration method

Some methods of separation of substances are discussed below:

  1. Winnowing

This is a separation process in which the mixture of substances is blown in air so that the lighter substances get dispersed by wind and the heavy substances can be separated. Example- separation of grain from husk is done by farmers using winnowing shovels. Winnowing drawing is given below:

Winnowing

  1. Threshing

Threshing is one of the methods of separation involving beating the stalk of grains against an object to separate grains from stalks. This process is typically used in farming.

  1. Sieving

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Sieving is a separation process in which a semi porous barrier (or sieve) is used to separate the mixture to obtain the required portion of mixture. Example- Sieves are used to remove impurities from flour.

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  1. Handpicking

Handpicking is a separation process involving selective picking of unwanted particles by hand. Example- picking marbles from a bucket of water.

  1. Magnetic Separation Method

This method is used in separating components of a mixture of magnetic substances or mixtures containing magnetic components. In this method, the substance which needs to be separated is passed through a conveyor belt attached to magnetic rollers. The magnetic rollers attract the magnetic portion of the substance which is collected in separator drums. In this way, the magnetic component(s) is separated from the non-magnetic component(s). This is often used in separation of solid solid mixture. Magnetic Separation images are given below:

Magnetic separation

Other common methods of separation are sedimentation, evaporation and filtration.

Commonly Asked Questions

Q: Why is separation important in chemistry?
A:
Separation is crucial in chemistry for several reasons: it allows us to purify substances, isolate desired products from reactions, analyze complex mixtures, and extract valuable components from natural sources. It's fundamental in both research and industrial applications of chemistry.
Q: What are methods of separation in chemistry?
A:
Methods of separation in chemistry are techniques used to isolate individual components from a mixture. These processes exploit differences in physical or chemical properties of the substances, such as size, solubility, boiling point, or magnetic properties, to separate them from each other.
Q: What's the difference between a pure substance and a mixture?
A:
A pure substance consists of only one type of atom or molecule, while a mixture contains two or more different substances that are physically combined but not chemically bonded. Pure substances have consistent properties, while mixtures' properties can vary based on composition.
Q: What is the principle behind using a Dean-Stark apparatus?
A:
The Dean-Stark apparatus is used for the separation of water from organic compounds through azeotropic distillation. It collects and measures the water produced in a reaction or removed from a mixture, allowing for both separation and quantification.

Separation Techniques for Mixtures

Separations are complex and may require several different methods and much time before the final determinative step. The separation process used depends on the component of the mixture and their characteristic properties.

There are various methods of separating mixtures, they can be categorized as:

  • Separations involving phase changes

  • Separations involving extraction

  • Separations involving chromatography

  • Separations involving ion exchange resins

  • Separations involving floatation

Separation Involving Phase Change

There are 3 phases of matter that we see in everyday life namely solid, liquid and gas. When a liquid changes into a gas, this gas is called a vapor. When a component of a mixture can undergo phase change, separating components of a mixture becomes easier. The simplest separation process example is the removal of water from any solid substance. When the substance is heated the water (liquid) changes to vapor and separates from the solid compound. This separation process is called volatilization. Another important method for separating the components of a mixture is distillation. Distillation is a separation process in which vapor is produced by heating a liquid in a vessel. The vapors are then condensed followed by collection in another vessel.

Separations Involving Extraction

An extraction is a separation process involving the selective transfer of a compound(s) from one liquid to another immiscible liquid (liquid-liquid extractions) or from a solid to a liquid (solid-liquid extraction).

Separating Funnel Method

Separating funnel method is a common method used for separating the components of a mixture. A separatory funnel is the simplest type of extraction vessel. This method of separation is utilized to separate two immiscible liquids. Example - Oil and water mixture. Separating funnel diagram is given below:

Seperating funnel

Image of separating funnel

Separations Involving Chromatography

Chromatography is one of the multistage separation techniques based on the principle of different rates between compounds in adsorbing on a surface or dissolving in a thin film of liquid. The two major chromatographic separation techniques at work used for separating the components of mixture are displacement and partition chromatography. Other common chromatographies are paper, thin layer, high performance, gas chromatography and gel permeation.

Also, students can refer,

Separation Involving Ion Exchange Resins

Ion exchange is a separation process used for separating mixtures in which one type of ion in a compound is exchanged for a different type i.e., cation for cation and anion for anion. For example, calcium, iron and magnesium ions can be removed from water by using sodium ions.

Separation Involving Flotation

Flotation is a separation process performed by using a gas to cause selected solid particles to rise to the surface from a mixture of particles suspended in a liquid. Flotation without involving a gas can be done by using a liquid that will selectively coat the solid particles.

Also check-

NCERT Chemistry Notes:

Commonly Asked Questions

Q: How do you choose the appropriate separation method for a mixture?
A:
Choosing a separation method depends on the physical and chemical properties of the components in the mixture. Consider factors like particle size, solubility, boiling point, and magnetic properties. The goal is to exploit the largest difference in properties between the components.
Q: What is filtration, and when is it used?
A:
Filtration is a method used to separate solid particles from a liquid or gas. It's used when there's a significant size difference between the particles and the fluid. The mixture passes through a filter that allows the fluid to pass while retaining the solid particles.
Q: How does distillation work?
A:
Distillation separates liquids with different boiling points. The mixture is heated, causing components to vaporize at different temperatures. The vapors are then cooled and condensed back into liquids. This process allows for the separation of liquids with different volatilities.
Q: What is chromatography, and how does it separate mixtures?
A:
Chromatography is a versatile separation method that relies on the different affinities of mixture components for a stationary phase and a mobile phase. As the mixture moves through the system, components separate based on how strongly they interact with each phase.
Q: How does centrifugation separate mixtures?
A:
Centrifugation uses centrifugal force to separate components based on their density. When a mixture is spun at high speeds, denser components move outward while less dense components remain closer to the center, allowing for separation.

Frequently Asked Questions (FAQs)

Q: How does field-flow fractionation separate particles?
A:
Field-flow fractionation separates particles or macromolecules based on their diffusion properties in a fluid flowing through a thin channel. An external field (gravitational, electrical, thermal) is applied perpendicular to the flow, causing particles to separate based on their interaction with this field.
Q: What is the difference between analytical and preparative chromatography?
A:
Analytical chromatography is used to identify and quantify components in a mixture, typically using small amounts of sample. Preparative chromatography is used to isolate and collect larger quantities of purified components for further use or analysis.
Q: How does vacuum filtration differ from gravity filtration?
A:
Vacuum filtration uses a pressure difference created by a vacuum to force liquid through a filter, while gravity filtration relies solely on gravitational force. Vacuum filtration is faster and more efficient, especially for separating fine particles or viscous liquids.
Q: What is the principle behind using a centrifugal extractor?
A:
A centrifugal extractor combines the principles of centrifugation and liquid-liquid extraction. It uses centrifugal force to rapidly mix and then separate two immiscible liquids, allowing for efficient extraction of compounds from one liquid phase to another.
Q: How does size-exclusion chromatography separate molecules?
A:
Size-exclusion chromatography, also known as gel filtration, separates molecules based on their size. The stationary phase consists of porous beads. Smaller molecules can enter the pores and take longer to pass through the column, while larger molecules are excluded and elute faster.
Q: What is the difference between distillation and pervaporation?
A:
Distillation separates liquids based on boiling point differences, while pervaporation uses a membrane to selectively allow one component of a liquid mixture to permeate and evaporate. Pervaporation can separate azeotropic mixtures that distillation cannot.
Q: How does ion exchange chromatography work?
A:
Ion exchange chromatography separates ions and polar molecules based on their charge. The stationary phase contains charged functional groups that interact with oppositely charged ions in the mixture. Ions are then eluted by changing the mobile phase composition.
Q: What is the principle behind using a hydrocyclone?
A:
A hydrocyclone uses centrifugal force to separate particles or droplets from a liquid stream. The mixture enters tangentially, creating a vortex. Heavier components move to the walls and exit at the bottom, while lighter components exit from the top.
Q: How does salting out work as a separation technique?
A:
Salting out involves adding a salt to an aqueous solution to decrease the solubility of certain compounds, causing them to precipitate. This technique is often used in protein purification or to separate organic compounds from water.
Q: What is the difference between normal-phase and reverse-phase chromatography?
A:
In normal-phase chromatography, the stationary phase is polar and the mobile phase is non-polar, while in reverse-phase chromatography, the stationary phase is non-polar and the mobile phase is polar. This affects how different compounds are retained and separated.