Mixtures and Ways of Separating Mixtures
In chemistry, the material is made by the physical combination between two similar or different compounds that are mixed together in the form of a solution, colloids, and suspensions. The identities of such compounds are also retained. This is known as a mixture. But, they do not react chemically and are not certainly in a definite ratio. The various components from which the mixture is formed have their own physical properties. There are two types of a mixture such as homogeneous and heterogeneous.
For example: If a mixture is made by mixing water and sugar then the mixture maintains the properties of both elements.
Types of Mixtures
Homogeneous Mixtures:- These are the types of mixture in which two or more compounds mixed are distributed uniformly throughout the mixture. For example, Air and saline solution
Heterogeneous Mixtures:- These are the type of mixture in which two or more compounds are mixed unevenly or unequally. For example Oil in water and Sand in water.
Methods of Separation of Mixtures
The process or method of separation of different components of a mixture by the physical method is known as the separation of mixtures.
The choice of techniques of separating mixture depends upon mixture type and difference in the chemical properties of the components of the mixture.
Different Ways of Separating Mixtures
Some of the common techniques used in separating mixtures are as follow:
Separating funnel
Chromatography
Evaporation
Simple distillation
Fractional distillation
Centrifugation
Separating Funnel
A separating funnel is mostly used to segregate or separate the mixture's components between two immiscible liquid phases. The mainly aqueous phase and organic solvents are the two immiscible liquid phases found in this method respectively. The mechanism of separation depends upon the unequal density of the liquids. The liquid particles with more density are responsible for forming the lower layer and the upper layer is formed by the liquid having lesser density. This technique is used to separate oil and water.
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Chromatography
The separation technique is used to separate the mixture components by passing them in the suspension or solution or as a vapor over a medium in which the mixture constitutes or components move at different rates. This technique is dependent on the various properties of compounds present in two phases i.e mobile and stationary phases.
The technique involves dissolving the sample in a specific solvent known as a mobile phase which may be liquid or gas. This specific solvent is then passed over another phase present called a stationary phase. The separation is based upon different speeds at which different components of a mixture travels.
Types of Chromatography
Paper Chromatography
Thin layer Chromatography (TLC)
Column Chromatography
Gas Chromatography
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Evaporation
Evaporation is a method used to separate either a homogeneous mixture, usually two dissolved salts, or a solution consisting of a soluble solid and a solvent. The process typically involves heating the solution until the organic solvent evaporates and no liquid remains behind as it turns into a gas and leaves behind the solid components.
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Simple Distillation
An effective method used to separate a mixture that consists of two or more, pure or miscible liquids is known as distillation. It is a purification process in which the components of the liquid mixture are first vaporized and then condensed followed by isolation. In simple distillation, when the mixture is heated then the most volatile component vaporizes first at a lower temperature. The vapor moves through a cooled tube (condenser) and is collected after it gets condensed into a liquid state.
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Fractional Distillation
Fraction distillation is a technique used to separate a mixture that comprises two miscible liquids. The process implicates the heating of a liquid up to its boiling point. But, the difference in the boiling points of both the liquids should be less than 25K.
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Centrifugation
Centrifugation is a technique used for the separation of tiny solid particles from a liquid that can easily pass through a filter paper. Centrifugation is used for carrying out the separation of these insoluble particles where normal filtration fails to work well. The centrifugation depends upon the viscosity of the medium, speed of rotation, shape, size, and density of the particle. This technique is based on the principle that lighter particles stay at the top and heavier or denser particles are forced to move at the bottom when spun rapidly. The apparatus used for the centrifugation technique is called a centrifuge. The centrifuge mainly includes a centrifuge tube holder called a rotary. It holds balanced centrifuge tubes that contain an equal amount of solid-liquid mixtures.
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FAQs on Separation of Mixtures
1. What is meant by the separation of mixtures in Chemistry?
The separation of mixtures is a set of physical processes used to isolate the individual pure substances from a mixture. Since the components in a mixture are not chemically bonded, they retain their individual properties. These processes exploit the differences in physical properties such as boiling point, particle size, density, solubility, or magnetic properties to separate the components.
2. Why is it important to separate the components of a mixture?
Separating mixtures is essential for several reasons:
To remove undesirable or harmful substances: For example, purifying water by removing impurities and contaminants to make it safe for drinking.
To obtain a useful or valuable component: For instance, separating petrol, diesel, and kerosene from crude oil through fractional distillation.
To obtain a substance in its pure form for scientific analysis: Scientists need pure samples to study their properties and chemical behaviour accurately.
3. What are some common methods for separating mixtures with examples?
There are several common methods based on the nature of the mixture's components:
Filtration: To separate an insoluble solid from a liquid (e.g., sand from water).
Evaporation: To separate a soluble solid from a liquid (e.g., salt from saltwater).
Sublimation: To separate a substance that turns directly from solid to gas from one that doesn't (e.g., camphor from salt).
Centrifugation: To separate suspended particles from a liquid based on density (e.g., cream from milk).
Distillation: To separate two miscible liquids with different boiling points (e.g., alcohol from water).
Chromatography: To separate different dissolved components of a mixture (e.g., different pigments in a drop of ink).
4. How can you separate a mixture of ammonium chloride and common salt? Explain the process.
A mixture of ammonium chloride and common salt can be separated using the process of sublimation. Ammonium chloride is a sublime substance, meaning it turns directly from a solid into a gas upon heating, while common salt is not. The procedure is as follows:
The mixture is taken in a china dish and heated gently.
An inverted funnel is placed over the dish to collect the vapours.
As the mixture heats, the ammonium chloride turns into vapour, leaving the common salt behind.
The ammonium chloride vapour rises, cools, and solidifies on the inner walls of the funnel, from where it can be scraped off.
5. What is the difference between evaporation and distillation for separating mixtures?
The key difference lies in what components are recovered. In evaporation, a soluble solid is separated from a liquid by heating the solution until the liquid turns into gas and escapes, leaving the solid behind. You only recover the solid. In distillation, the liquid is heated to form vapour, which is then cooled and condensed back into a pure liquid in a separate container. This method allows you to recover both the liquid and the solid (if non-volatile).
6. How does centrifugation work to separate components like cream from milk?
Centrifugation works on the principle that denser particles are forced to the bottom and lighter particles stay at the top when a mixture is spun rapidly. In a centrifuge, milk is spun at high speed. The denser skimmed milk is forced outwards towards the bottom of the container, while the lighter cream (fat particles) accumulates in the centre and at the top. This allows the cream to be easily separated.
7. How is chromatography used in real-world applications?
Chromatography is a powerful separation technique with many real-world applications due to its high precision. For example:
In forensic science, it is used to separate pigments from ink on a document to identify the pen used, or to detect traces of drugs in blood or urine samples.
In the pharmaceutical industry, it is used to purify drugs and ensure their chemical composition is correct.
In food analysis, it helps identify artificial dyes and flavouring agents in food products.
8. Why can't a simple magnet be used to separate a mixture of salt and sugar?
A magnet can only separate mixtures where one of the components has magnetic properties. This technique works by attracting magnetic materials and leaving non-magnetic ones behind. Neither salt (sodium chloride) nor sugar (sucrose) are magnetic. Therefore, a magnet will have no effect on either substance and cannot be used to separate them. This method is effective for mixtures like iron filings and sand.
9. For the CBSE Class 9 syllabus 2025-26, which separation techniques are most important?
As per the CBSE Class 9 syllabus for 2025-26, students should focus on understanding the principles and applications of several key techniques from the chapter 'Is Matter Around Us Pure?'. These include:
Evaporation
Centrifugation
Separating funnel for immiscible liquids
Sublimation
Chromatography
Distillation and Fractional Distillation
