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Separation of Mixtures

  • Last Updated : 14 Jul, 2021

A mixture is composed of more than one pure form of matter. A mixture is a non-chemical combination of two or more substances. The majority of the materials in our environment are composites of two or more components. Mixtures are classified as either homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition, whereas heterogeneous mixtures are not.

Air is a homogeneous mixture, whereas oil in water is heterogeneous. Several physical methods can be used to separate homogeneous and heterogeneous mixtures into their constituents. The separation techniques used are determined by the type of mixture and the differences in the chemical properties of the constituents of a mixture.

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We’ve understood that the majority of natural substances are not chemically pure. To separate individual components from a mixture, various separation methods are used. Separation allows you to study and use individual components of a mixture. Heterogeneous mixtures can be separated into their constituents using everyday physical methods such as handpicking, sieving, and filtration. Separation of the components of a mixture may necessitate the use of specialized techniques.



Method of Separation of Mixtures:

  • Handpicking
  • Threshing
  • Winnowing
  • Sieving
  • Evaporation
  • Distillation
  • Filtration or Sedimentation
  • Separating Funnel
  • Magnetic Separation

Let us go over them in more detail below.

Handpicking

Handpicking is used to separate mixtures where one of the components is in small quantities. Handpicking is a technique used to separate undesirable substances such as small pieces of stone from wheat, rice, and pulses. Foodgrains with small pieces of stone are transported in a flat container. Hands pick up the stones from the grains one by one and throw them away. Only food grains remain after all the stone fragments have been removed.

Threshing

When a food grain crop, such as wheat or paddy, reaches maturity, it is harvested from the field. The harvested crop is then sun-dried. We receive bundles of dried crop plant stems or stalks with grains attached at the top. A thin layer of chaff covers the grains attached to the stems or stalks. Each stalk is densely packed with chaff-covered grains. Grains are separated from stems and stalks, as well as chaff.

The process of threshing separates the grains from the stems or stalks. Threshing is the process of beating wheat or paddy stems to separate grains from the stems and the chaff that covers the grains. Crop plant stalks and stems, as well as chaff, are soft materials, whereas grains are extremely hard. Because the stalks and chaff are soft, they can be broken into pieces when beaten, but the grains are unaffected. Threshing is accomplished by holding bundles of stems in one’s hands and striking them against a hard surface. As a result, the grains separate from the stems.

Threshing is also done with the assistance of cattle. The harvested and dried crop plants are spread on the ground in a small area, and various cattle such as buffaloes and camels are made to walk in circles over them for an extended period of time. The cattle’s feet crush the stems or stalks, separating the grains from the stems. This crushing also breaks the chaff surrounding the grains, allowing the grains to be separated from the chaff. During the threshing process, the stalks are reduced to very small pieces known as hay, which is used as a dry fodder for cattle. The husk is made up of broken chaff. For the threshing process, a motorized machine known as a thresher is used.

Winnowing

When a farmer threshes wheat in his field, he gets a mixture of wheat grains and husk. Husk must be removed from wheat grains before they can be used. The husk is separated from the wheat grains by winnowing.



Winnowing is the process of separating husk from grains using the wind. Wheat grains are heavy, whereas husk is light. Winnowing is accomplished with a winnowing basket. The farmer stands on a higher platform than the ground and shakes his winnowing basket continuously to allow the mixture of wheat grains and husk to fall from a height.

Because wheat grains are heavy, they fall vertically to the ground and form a heap of wheat grains. Because husk particles are lighter, they are carried further by the wind. As a result, the husk forms a separate heap away from the wheat grain heap. In this manner, the husk is separated from the wheat grains.

Winnowing is a technique used to remove the husk from grains such as wheat and rice. We cannot separate small stone particles from wheat using the winnowing process. This is due to the fact that stone particles are quite heavy and cannot be carried a long distance by wind.

Sieving

A sieve is a shallow container with small holes at the bottom. In some cases, an iron mesh can also be used as a sieve. Sieving is the process of parting a mixture using a sieve. Sieving is used to separate solid mixtures that contain components of varying sizes.

The mixture, which contains components of varying sizes, is placed in a sieve, and the sieve is continuously moved back and forth. The larger particles of the mixture cannot pass through the sieve’s small holes and thus remain trapped in the sieve.

The mixture separates into two components: one with small particles and one with larger particles. The size of the sieve’s holes is determined by the size of the particles of the material to be separated from the mixture. Different substances are separated using sieves with varying sizes of holes.

  • Wheat brought from the fields still contains impurities such as stones, stalks, and husks. Impurities are removed from wheat before grinding in a flour mill via a sieving process. A bag of wheat is poured through an iron mesh slanting sieve. The wheat grains pass through the Sieve, leaving behind pieces of stone, talk, and husk.
  • Sieving is used to obtain fine sand. Coarse sand with larger particles and pebbles is placed on a sieve made of a large iron held in a slanting position. Fine sand particles pass through the iron mesh but are left behind.
  • Sieving is also used to separate similar objects of varying sizes. Cashew nuts of various sizes are separated in cashew nut factories through the sieving process.

Evaporation

Evaporation is a technique for separating a mixture, most commonly a solution of a solvent and a soluble solid. The solution is heated until the organic solvent evaporates, turning into a gas and mostly leaving behind the solid residue in this method.



Evaporation is a method of separating homogeneous mixtures containing one or more dissolved salts. The method separates the liquid from the solid components. Typically, the process entails heating the mixture until no liquid remains. Unless it is not necessary to isolate the liquid components, the mixture should only contain one liquid component before using this method. This is due to the fact that all liquid components will evaporate over time. Evaporation is an effective method for separating a soluble solid from a liquid.

Distillation

Distillation is a fast way to separate mixtures of two or more pure liquids. Distillation is a purification method that involves vaporizing the constituents of a liquid mixture, then condensing and isolating them. A mixture is heated in simple distillation, and the most volatile component vaporizes at the lowest temperature. The vapor condenses back into liquid after passing through a cooled tube (a condenser). The collected condensate is known as distillate.

Several important pieces of equipment are depicted in the figure above. A heat source, a test tube with a one-hole stopper attached to a glass elbow, and rubber tubing are all present. The rubber tubing is inserted into a collection tube filled with cold water. Other more complicated distillation assemblies can also be used, particularly to separate mixtures of pure liquids with similar boiling points.

Filtration or Sedimentation

The most common method of separating a liquid from an insoluble solid is filtration. Consider the case of a sand-water mixture. In this case, filtration is used to remove solid particles from the liquid. Various filtering agents, such as filtering paper or other materials, are commonly used.

Sedimentation is the process by which heavier impurities in a liquid, typically water, settle to the bottom of the container containing the mixture. It takes some time to complete the process.

Separating Funnel

This method is used with immiscible liquids (those that do not mix together). The mechanism works by exploiting the unequal density of the particles in the mixture. Using this technique, oil and water can be easily separated. In the process, a separating funnel is used.

Separating funnel process

Once the liquids are in the funnel, you must wait for them to form two layers. The denser liquid sinks to the bottom, while the other liquid rises to the surface. At the bottom, a conical flask is placed to collect the denser liquid. The valve allows you to control when and how much liquid is allowed to pass through to the conical flask.



Example: A separating funnel, as shown in the diagram, can separate oil and water.

Magnetic Separation

Magnetization is a method of attracting magnetic materials. Magnetic separation is the process of separating mixtures of two solids, one of which has magnetic properties. It is based on the distinction between magnetic and non-magnetic materials. Iron particles in the mixture of iron and Sulphur are attracted to the magnet and separate from the non-magnetic substance.

Solved Questions

Question 1: What do you mean when you say “mixture separation”?

Answer:

A mixture is composed of more than one pure form of matter. Mixtures are classified as either homogeneous or heterogeneous. Homogeneous mixtures have a uniform composition, whereas heterogeneous mixtures do not. Mixture separation refers to the separation of homogeneous and heterogeneous mixtures.

Question 2: What method will you use to separate a sand and sugar mixture?

Answer:

The sugar would dissolve in water. After that, the solution could be poured off and the remaining sand washed with a little more water. Separate the two by heating the water to separate it from the sugar. In water, the sugar would dissolve. The solution could then be poured off and the remaining sand washed with a little more water. Heat the water to separate it from the sugar, and then separate the two.

Question 3: Explain how to separate a sand-salt mixture.



Answer:

To separate common salt and sand from a mixture, the processes of filtration and evaporation are used. Filtration can separate sand from a sand-salt solution mixture (salt dissolved in water). After filtration, sand remains as a residue on the filter paper. Common salt can now be obtained by boiling the filtrate. When water boils, it evaporates completely, leaving only salt behind. This is referred to as evaporation. 

Question 4: What method will you use to separate a salt and sugar mixture?

Answer:

Evaporation (the process of converting a liquid to vapour) can separate the sugar and salt solution, and if the water is completely evaporated, we will get separated sugar from the mixture, whereas if the solution is dissolved in alcohol, we will get salt while sugar will be dissolved in alcohol.

Question 5: What is the name of the solvent used to separate a Sulphur and Carbon mixture?

Answer:

To separate the carbon and Sulphur mixture, a carbon disulphide solution can be used. Carbon is undissolved in the solution, but Sulphur dissolves. This mixture is then filtered to remove the carbon before being evaporated to extract the Sulphur.

Question 6: What is the method and process to separate a mixture of sodium chloride and sand?

Answer:

The filtration and distillation processes can be used to separate a mixture of sodium chloride and sand in water. When the solution is filtered, the sand remains on the filter paper while the liquid passes through. The solution is then distilled. During distillation, water evaporates, then condenses and cools to become liquid. Water will be collected in the beaker. Meanwhile, salt will remain in the distillation flask as a residue.

Question 7: What method will you use to separate iodine from an iodine-and-common-salt mixture?

Answer:

Sublimation is the most effective method for separating iodine from common salt (NaCl). Because iodine is sublimable, it will change from solid to vapour when slightly heated, and the iodine vapours can be collected while common salt remains solid.

Question 8: Explain the method to separate a mixture of iron filling and powdered carbon?

Answer:

Using magnetic separation We can separate a mixture of iron filings and powdered carbon using a magnet. The attraction of magnets by iron serves as the foundation for the separation of iron fillings and powdered carbon.




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