Methods of Separation

Through this concept, the students will get a basic idea about the methods of separation. They will know what dry and wet mixtures are and how the essential elements of different mixtures can be separated.

After reading the concept, students will be able to:

Explain methods of separating mixtures.
Understand what is hand picking.
Define winnowing method and when it is applied.
Define threshing process.
Explain the filtration process.
Analyse when to apply the sedimentation and decantation process to separate mixtures.
Understand why magnets are used during the magnetic separation method.
Explain about water cycle and its basic steps like water evaporation, condensation, precipitation and collection.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept of the Methods of Separation provided in PDF format.

In our day-to-day life, we have to separate different components from mixtures using different methods.

Examples: While making tea, we have to separate tea leaves with a strainer to get the tea, grains are separated from stalks, milk is churned to separate the butter etc.

Separation of substances can be done under two conditions—

i) Dry conditions

ii) Wet conditions

Methods of Separation of Substances Under Dry Conditions:

1. Hand-Picking:

This method involves picking out the impurities by hand and separating them from others.
The separated substances could be the impurities or the separated substances could be useful.
This method is effective in the case of big-sized impurities.

Example: Hand-picking gravels and stones from grains.

2. Threshing:

Threshing is carried out after harvesting crops.
This method is useful in separating the grains from the dried stalks.
Farmers continuously beat the dry stalks. This is how the grains are separated before getting ground.
Traditionally this process is done manually, but nowadays, threshing machines are available that help in separating huge quantities of grains.

Example: Combine harvester.

3. Winnowing:

Once the grains are threshed, the husk is removed before grinding or before sending the grains to the market.
Winnowing helps in the separation of chaffs from grains.
In winnowing, the lighter and heavier particles are separated from any mixture in presence of wind or blowing air.
The mixture is dropped to the ground and meanwhile, the heavier grains get accumulated at a certain place and the lighter chaff blows away.

4. Sieving:

This method is used if someone wants to separate substances of varying sizes from a mixture.
A sieve is used in this method.
The smaller particles of the mixture pass through the sieve, but the bigger particles are left behind on the sieve.

5. Magnetic Separation:

This method is used when one of the components in the mixture is magnetic.
The magnetic components could be iron, cobalt, nickel, steel, or other magnetic substances.

Example: By using magnets, one can separate iron-bearing minerals from sand particles and iron filings from sulphur powder.

Methods of Separation of Substances Under Wet Conditions:

To separate insoluble solid particles from solutions, we use the following methods of separation.

1. Sedimentation and Decantation:

This method is applied when one has to separate insoluble substances heavier than the liquid.
The insoluble substances are allowed to settle at the bottom of the container on their own due to gravity.
It is called sedimentation, and the substances that settle down are called sediments.
The process of decantation involves the transfer of the clear liquid from the container without unsettling the sediment.
The clear liquid obtained is called supernatant.

Example: The separation of soil and sand is done from muddy water by sedimentation and decantation.

2. Filtration Process:

In this process, insoluble solids can be separated from a liquid using filter paper.
Filter papers have tiny pores that let only liquids pass through them.
If we pass any solution through filter paper, all undissolved solid particles get collected on the filter paper, whereas the liquid passes through.

Example: The filtration process can separate a mixture of chalk powder and water.

3. Evaporation:

The conversion of water into vapour by heating it to its boiling point is termed evaporation.
Evaporation is used to separate impurities that are soluble in that particular solvent of the mixture.
The mixture containing the soluble impurities is heated.
Consequently, the solvent evaporates and is collected separately.
The impurities like salt or sugar are left behind as the residue.

Example: Separation of salt or sugar from water is carried out by evaporation.

4. Distillation:

It is used to separate and collect a liquid from a mixture containing a soluble solid.
The solution is gradually heated in a flask till it starts to boil.
The vapour produced in the flask is passed through a condenser, where it condenses into a liquid.
This is how the pure liquid is obtained.

Example: Pure water can be separated from salt water by applying the process of distillation.

New Words:

Chaff: The seed coverings and other residual matter that get separated from the seeds while threshing grains.

Husk: The outer covering of seeds.

Magnetic: Having the ability to attract a magnet.

Did You Know?

The water cycle is nothing but a phenomenon of evaporation and condensation. In this process, the water evaporates from the surface of the Earth and rises into the atmosphere. Then it cools and condenses into clouds and falls again to the surface as precipitation.

Crude oil is a complex mixture that exists as a liquid in the Earth's crust. Different separation techniques are used to purify various constituents such as natural gases, gasoline, diesel, jet fuel, lubricating oils, asphalt, etc., from the crude oil.