Have you ever noticed how the tea is being filtered before it is served? This is done to remove the waste products which cannot be consumed. Separation methods include removing stones from rice and separating tea leaves from tea and so on. Separation methods are utilized to get the desired product after removing harmful or unwanted substances from the mixture. To learn more about methods of separation, read the below article.

Need of Separation

The mixtures are separated into their components for various purposes, such as;

1. To remove an undesirable component
2. To remove a harmful component
3. To obtain the pure sample of a substance
4. To obtain a useful component

Methods of Separation

Many of the materials around us are mixtures. These mixtures have two or more substances mixed in them. It may not be possible to use a mixture as such in homes and industries. Different substances in a mixture possess different properties like size, hardness, density, solubility, texture, weight, etc. These differences in their physical properties are used to separate them from a mixture.

Depending on the type of mixture, different methods of separation are used. Some of the common methods of separation are;

1. Filtration
2. Hand-picking
3. Threshing
4. Winnowing
5. Sieving
6. Sedimentation and decantation
7. Magnetic separation
8. Centrifugation
9. Evaporation
10. Distillation

Now let’s discuss each separation method in detail.

Filtration

Filtration is the process of separating insoluble solids from a liquid mixture by using a filter. The filter could be in the form of a strainer, a sieve, a muslin cloth or filter paper.

Filtration Process

The insoluble solid mixture and the liquid are poured into a filter paper cone fixed in a funnel by using a glass rod as a guide. The liquid flows through the filter paper and collects in the beaker beneath the funnel. Solid particles do not pass through the filter paper and remain on it. The solid substance left behind on the filter paper is called the residue. The clear liquid obtained is called filtrate. In this way, a mixture of insoluble solids in a liquid is separated into a solid and clear liquid.

Applications of Filtration

1. When boiling tea is poured over a strainer, the tea leaves remain in the strainer and tea gets collected in the cup below. This process of separation of tea leaves from the prepared tea is called filtration. In this, the strainer acts as a filter.
2. A mixture of chalk and water is separated by filtration. When a mixture of chalk and water is poured on the filter paper fixed in a funnel, then clear water passes through the filter paper and collects as filtrate.
3. A mixture of sand and water can also be separated by filtration.
4. Filtration is also used for separating paneer.
5. Fruit pulp and seeds can be separated from the fruit juice by using a sieve.
6. For lab experiments, filter paper is used as a filter.

Hand-picking

Hand-picking means taking it out by hand. Hand-picking is a method of manually separating small substances visible to the naked eye from a mixture. It is used to separate substances that differ in size, shape, or colour and that can be picked up by hand because they are typically present in small quantities.

For example, the hand-picking method is used to separate small stones from food grains like pulses, rice and wheat. The pieces of stone are picked up from the food grains by hand and thrown away.

Threshing

Threshing is the process in which stalks (such as stalks of wheat, paddy, etc.) are beaten to separate grains from the stalks and from the chaff that covers the grains. The separation method is based on the fact that crop plant stalks and chaff are soft materials, whereas grains are extremely hard. Because stalk and chaff are soft, they can be broken into pieces when beaten, but the grains are unaffected.

Threshing is accomplished by holding bundles of stalks in your hands and hitting them against a hard surface. Threshing is accomplished with the assistance of bullocks or a machine known as a thresher.

Winnowing

Winnowing is the method of separating heavier and lighter components of a mixture with the help of wind or blowing air.

In this process, a mixture of grain and husk is made to fall from a height with the wind blowing over it. The husk, being lighter, blows away and forms a heap some distance away. The heavier grains fall to the ground and form a separate heap.

Applications of Winnowing

1. The winnowing method is used to separate the husk from various types of grains like wheat, rice, etc.
2. Winnowing can be used to separate sand from sawdust or sand from dried leaves. Sawdust and dried leaves being lighter get blown away by wind and form a separate heap at a distance.

Sieving

Sieving is a method of separating substances of different sizes using a sieve. A sieve is a type of strainer that consists of a fine iron mesh attached to a wooden or iron frame. The sieves could be of different sizes depending on the size of the substances to be separated. Sieving is used to separate substances that cannot be easily hand-picked due to their small size or presence in large quantities.

In the separation of substances by sieving, the mixture is placed in a sieve and the sieve is continuously moved back and forth. Smaller and finer particles pass through the holes on the sieve and can be collected below, while larger particles remain in the sieve.

Applications of Sieving

1. The flour that we get from the flour mill has some bran mixed in a fine flour. Sieving is used to separate the bran from fine flour.
2. We require fine sand to be mixed with cement before plastering the walls of a house. The sieving method is used to obtain fine sand.

Sedimentation and Decantation

The Sedimentation and Decantation process has been explained in detail below:

Sedimentation

Sedimentation is the process of settling down of heavier solids in water when the mixture is allowed to stand undisturbed for some time. It is used to separate insoluble solids from a solid-liquid mixture. For example, rice and pulses commonly contain small stones and dust particles. Water is added to the pulses after small stones are removed by hand. The heavier pulses settle down, while water with dissolved impurities from the upper layer rises. This is referred to as sedimentation. The pulses that settle at the bottom are called sediments.

Decantation

Decantation is a process of pouring out the top layer of liquid into a separate container leaving behind the solid particles or sediments at the bottom.

For example,

1. In cleaning rice and pulses, the pouring out of dirty water containing impurities is called decantation.
2. Decantation is also used to separate water after boiling the vegetables.

Magnetic Separation

Magnetic separation means ‘separation of a mixture by using a magnet’. We know that a magnet attracts iron. This property of iron is used to separate it from a mixture. For example, a magnet can be used to separate a mixture of iron filling and sulphur powder. This is because iron filings are magnetically attracted, whereas sulphur powder is not.

Evaporation

The changing of a liquid into vapour is called evaporation. Evaporation is used to obtain a solid substance that has dissolved in water. Although evaporation takes place at room temperature, it is much faster when the water is heated.

When the mixture is heated till all the water evaporates in the air, only the dissolved substance is left behind as a solid residue. For example, The common salt dissolved in water can be separated by the process of evaporation. The process involved is as follows:

In a porcelain dish, a solution of common salt and water is gently heated using a burner. The water present in the salt solution will form water vapours and escape into the atmosphere. When all of the water in the common salt solution evaporates, the common salt is left in the porcelain dish as a white solid.

The process of evaporation is used to obtain common salt from seawater. Seawater contains a variety of salts, including common salt, which is dissolved in it. The trapped seawater is allowed to stand in the shallow pits. Water is left to dry in these pits. The heat of the sun gradually evaporates the water leaving behind the solid salts. This solid salt is a mixture of salts from which common salt is obtained by further purification.

Distillation

Distillation is the process of heating water to form water vapour and then cooling the hot water to get back liquid water. Distillation can be represented as;

\(\mathop {{\text{Water}}}\limits_{\left( {{\text{Liquid}}} \right)} \mathop  \rightleftarrows \limits_{{\text{Cooling}}}^{{\text{Heating}}} \mathop {{\text{Water}}\,{\text{vapour}}}\limits_{\left( {{\text{or}}\,{\text{steam}}} \right)} \)

The changing of water into water vapour on heating is called evaporation. And the changing back of hot water vapour into liquid water on cooling is called condensation. Thus, distillation involves two processes: evaporation followed by condensation.

For example,
Saltwater contains salt and water. We can obtain pure water from the salt solution by the method of distillation. The water obtained is also known as distilled water.

Centrifugation/Churning

It is a method of separating the lighter substances from the heavier ones by churning or rotating the mixture quickly. It is a common method at home to separate butter from the cream. The cream is churned at high speed. On churning, the butter particles separate and being lighter, come on top of the liquid.

FAQs

Q.1. What are the \(7\) methods of separating mixtures?
Ans: The seven methods of separating mixtures are as follows:
1. Hand-picking
2. Threshing
3. Winnowing
4. Sedimentation and decantation
5. Filtration
6. Evaporation
7. Magnetic separation

Q.2. What are \(3\) examples of separation techniques?
Ans: Examples of separation techniques are evaporation, distillation and filtration.

Q.3. What are the \(4\) physical separation techniques?
Ans: The four physical separation techniques are as follows;
1. Hand-picking
2. Threshing
3. Winnowing
4. Filtration

Q.4. Why do we need for separation?
Ans: The need of separation of mixture is as follows:
1. To remove an undesirable component.
2. To remove a harmful component
3. To obtain the pure sample of a substance
4. To obtain a useful component

Q.5. What are some examples of physical separation?
Ans: Examples of physical separation are filtration, magnetic separation, evaporation, distillation, centrifugation, threshing, hand-picking, winnowing.

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