In this article, you will have an Introduction to Separation of Substances. In our daily lives, we use items such as sugar, table salt, water, milk, and so on. In many circumstances, we must separate the beneficial components from the undesirable or even hazardous components in any ratio. For example, the air we breathe contains a variety of gases.

Separation of substances is carried out to eliminate non-useful or hazardous components, extract valuable components, or remove contaminants to produce a pure sample. Varied materials have different properties, which can be used to distinguish mixes. Let us now study different methods used to separate the components of various types of mixtures.

Purposes of Separation of Substance

Before we use a substance, we need to separate harmful or non-useful substances mixed with it. Sometimes, we separate even useful components if we need to use them separately.
The substances to be separated may be particles of different sizes or materials. These may be solids, liquids or even gases.
Separation of substances can be done for the following purposes:(i) To remove an undesirable thing.
(ii) To obtain a desirable component.
(iii) To obtain a useful component.
(iv) To obtain a pure component.

Separating or dividing one thing from another is called separation, e.g. separation of stones from rice, tea leaves are separated from the liquid with a strainer while preparing tea, milk or curd is churned to separate the butter.

Methods for Separating Mixtures

There are several methods of separation. The separation method depends upon the nature of the property of constituent substances present in the mixture. When we want to separate the components of a mixture, we should first find some properties that would be different for different components. We can use some methods for separation which can be used in our daily life. These are discussed below:

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Handpicking

A method of separation to take out useless material by hand is known as handpicking. This method separates undesirable substances such as small stones from wheat, rice, pulses, etc. In other words, the process of separating slightly larger-sized particles (impurities) like stone, husk, dirt, etc., from the grains of wheat, rice, pulses, etc., is known as handpicking.

Threshing

When a farmer harvests wheat or paddy crop, he gets many stalks mixed with grains. Many grains are attached to the stalk. These grains have to be separated from the stalks. To separate them from stalks, the stalks are threshed (beaten) on a wooden board. Machines (threshers) and bullocks are also used to separate the grains. The process used to separate grains from stalks is called threshing.

Winnowing

Winnowing is the process of separating heavier and lighter components of a mixture by wind or by blowing air.
Farmers separate grains from the husk by the method of winnowing. They stand on a high platform and release the mixture of husk and grains from a winnow. Grains being heavy, fall nearer, and the husk is blown a little away by the wind. The separated husk is used for many purposes, such as fodder for cattle.
This method is used when one of the two components of a mixture is heavier than the other.

Sieving

A sieve is a shallow vessel having small holes at its bottom. We need to remove impurities from flour by using a sieve. The method of separating a mixture by using a sieve is called sieving. Sieving is used to separate those mixtures which have components of different sizes. Sieving allows the fine flour particles to pass through the sieve holes while the bigger particles remain above the sieve.

On a large scale, impurities like unwanted particles or husk are removed from grains before grinding them. Normally, a bag full of wheat is poured on a slanting sieve. The sieve removes stones, stalks and husk that may remain with wheat grains after threshing and winnowing.

Magnetic Separation

In this method, a magnet is used for picking up iron pieces, nails, pins, etc., from grains or any other commodity. On a larger scale, a powerful magnet is employed for separating scrap iron from nonmagnetic waste materials.

Sedimentation, Decantation and Filtration

We observed that sometimes, separation of mixture is not possible with the help of winnowing and handpicking. So, we use another process for the separation of a mixture. These are as follows:

Sedimentation

The process of settling of heavy solid particles in a mixture at the bottom of the vessel is known as sedimentation, e.g. when we mix up sand and water in a glass and stir it with a spoon or any other tool and wait for some time, we see that the sand lies at the bottom and clear water stands on it. The solid below is sediment, and the clear liquid above is known as the supernatant layer.

Decantation

The transfer of clean liquid from one vessel to another without disturbing the sedimented particles is decantation.
The same principle is used for separating a mixture of two liquids that do not mix, e.g. oil and water can be separated from their mixture by this process. If a mixture of such liquids can stand for some time, they form two separate layers. The component that forms the top layer can then be separated by decantation.

Filtration

Decantation is not enough for the complete separation of a solid-liquid mixture. This can be done better by filtration, in which the mixture is dropped on a porous material known as a filter. The liquid passes through the filter and comes down as filtrate. The insoluble solid left behind is known as the residue.
When you make tea, you filter it through a strainer having a wire gauze. The tea extract comes down as filtrate, and the boiled tea leaves are left behind as residue.
Filters may be a wide variety of materials like fine cloth, plastic gauze, cotton wool, filter paper, glass wool, sand, etc. They are used for different solids according to the size of their particles.

Loading

Sometimes the water of a river or canal is muddy or turbid due to hanging very fine clay particles. They cannot be removed by decantation or filtration. In such a case, loading is useful.
A piece of alum (phitkari)tied with a thread is moved in the turbid water. The alum dissolves in water, and the water begins to clarify. The clay particles become bigger and heavier and settle down. Now they can be removed using decantation or filtration.
The alum, in a way, loads (make heavy) the clay particles. Hence, the process is called loading. Instead of alum, many other soluble salts can also be used for loading.

Evaporation

Evaporation is the process by which we can separate soluble solids from a liquid-solid mixture. The process of conversion of water into its vapour is called evaporation.
This method is used when the unwanted component is in a liquid, say water, and when the component we require is solid in nature. In this method, the mixture is heated on a stove. The impure liquid evaporates, leaving behind the required solid component.
This process is used in making common salt near sea coasts. Seawater is allowed to be collected near the seashore in shallow and large pits. The sun rays heat the water, due to which it undergoes evaporation. The evaporating water leaves behind the salt. The residue left on evaporation is a mixture of salts. Common salt is separated from this mixture by further purification.

Centrifugation

Centrifugation is the process by which we can remove fine insoluble solids from a liquid-solid mixture in a machine called a centrifuge, which rotates at high speed. Due to the machine’s high speed, the solids are pushed towards the walls of the machine, and the liquid remains at the Centre. Thus, the mixture is separated.

Uses of Centrifugation

(a) In dairies, this process is used to separate cream from milk.
(b) In washing machines, this principle is used to squeeze out water from wet clothes.

Summary

Separation is necessary when we need to remove unwanted things. For example, you can remove unwanted chillies from food by picking them with your hand. There are many other instances where we need to separate one substance from another. This article taught us handpicking, threshing, winnowing, evaporation, loading, sedimentation, decantation, filtration, sieving, magnetic separation, and centrifugation.

FAQs

Q.1. What is Separation of Substances?
Ans: Separating or dividing one thing from another is called separation, e.g. separation of stones from rice, tea leaves are separated from the liquid with a strainer while preparing tea, milk or curd is churned to separate the butter.

Q.2. How would you obtain clear water from a sample of muddy water?
Ans: We will obtain clear water from a sample of muddy water by the process of filtration.
In this process, we use a piece of cloth for filtering muddy water. Because in a piece of cloth, small holes or pores remain in between the woven threads. These pores in a cloth can be used as a filter.
If the water is still muddy, impurities can be separated by filter paper with even smaller pores. A filter paper is one such filter that has very fine pores in it. A filter paper folded in the form of a cone is fixed onto a funnel. The mixture is then poured on the filter paper.
Solid particles in the mixture do not pass through it and remain on the filter paper, and finally, clear water is obtained.

Q.3. Why do we need to separate different components of a mixture? Give two examples.
Ans: Among different components of the mixture, many substances are harmful or not useful for us. To remove these harmful or useless components, we need to separate them. Examples:
(a) Tea leaves are separated from the liquid with a strainer while preparing tea.
(b) Stone pieces from wheat, rice or pulses are picked out by hand.

Q.4. How will you separate sand and water from their mixture?
Ans: We will separate sand and water from their mixture by the process of sedimentation and decantation.
Sedimentation: During this process, we leave the mixture for some time. After that, the heavier sand is settled down at the bottom.
Decantation After the above process, water is poured into another vessel and sand is left in the first vessel. Thus, sand and water will be separated from their mixture.

Q.5. Can water dissolve substances?
Ans: Water can dissolve a wide range of compounds, which is why it is such an effective solvent. And, because it dissolves more things than any other liquid, it is known as the “universal solvent.” This is critical for all living things on the planet.

Q.6. What is winnowing? Where is it used?
Ans: Winnowing separates heavier and lighter components of a mixture by wind or by blowing air. This process is used by farmers to separate lighter husk particles from heavier seeds of grain.

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