Separation Methods

The separation of substances from a mixture segregates different functional components and removes non-useful, harmful or impure substances. At least one product mixture from the separation is rich in one or more components of the starting mixture. In some cases, separation can break down the mixture into entirely pure ingredients. Separation takes advantage of differences in chemical or physical properties (size, shape, mass, density, chemical affinity, etc.) between the mixture’s components.

Methods of Separation:

1. Handpicking

• The process of directly removing by hand is called hand picking.
• The process of handpicking is used to separate slightly large impurities or particles like pieces of dirt, stone, and husk from wheat, rice, pulses, etc.
• The quantity of such impurities is primarily tiny.
• An example of handpicking is the removal of rice from pulses in a mixture of the two.  
• It is a well-known and popular method of separation.
• However, it faces the problem of being time consuming and unuseful for small-sized grains.

2. Winnowing

• The separation of the heavy and light components of a mixture by wind or by blowing air is called Winnowing.
• Farmers use it to separate light husk particles from heavy grain seeds.
• The husk’s particles get carried away by the wind. Seed grains get separated and form heaps near the platform to get winnowed.
• Winnowing has the benefit of successful removal of pests.
• This method, however, is not helpful for substances that are heavier than grains.
• An example of winnowing is the removal of husk from wheat. 

3. Threshing

• The threshing process involves plant stalks getting beaten to free the grain seeds.
• The process separates the grain from the plant stalk and is also done with the help of bullock carts and thresher machines. 
• Threshing is simply a process that results in the loosening of the stalk, while winnowing is used to separate grains from the stalk. 
• An example of threshing is the removal of small rocks or materials from grains. 
• The process of threshing can be carried out by hand, through animals, manual machines, and motorization. 

4. Sieving

• Sieving is the process that involves the separation of different components of a mixture having different sizes.
• A sieve separates fine particles that get passed through the sieve holes. The more significant impurities remain on the sieve.
• Generally, it is used in removing pieces of stalk, stone, and husk that usually remain with wheat after threshing and winnowing.
• Sieving has the advantage of being easy and low cost.
• On the other hand, sieving is time consuming and is a difficult process.
• For instance, the use of a sieve to separate stones from sand.

5. Sedimentation, Decantation, and Filtration

• Sedimentation, Decantation, and Filtration help separate lighter impurities that winnowing and handpicking may not be possible.
• Sedimentation is when the heavier component in a mixture settles at the bottom (generally, the liquid is water) and thus gets separated.
• Sedimentation is a low cost and simple method.
• When the water and the dust are removed, the process is called Decantation. The same method is used for separating a mixture of two liquids that do not mix. E.g., oil and water from their mixture.
• Decantation is quick and an easy technique.
• Filtration is the separation of solids from liquids or gasses by using a fine-pored filter medium. Only the fluid can pass through the filter medium and not solid. 
• Filtration is environmentally-friendly, simple and of low maintenance.

6. Evaporation

• Evaporation is the process of conversion of water into water vapor. Seawater has a lot of salt mixed in it like the common salt. Water gets heated by sunlight and turns into water vapor by evaporation when the seawater stands in shallow pits. Solid salts are left behind after the water completely evaporates.
• Often, we need to use more than one of these methods to separate the different substances present in a mixture. For example, salt and water mixture is separated using decantation, filtration, evaporation, and condensation (condensation is the conversion of water vapor into its liquid form).
• Evaporation provides a high amount of purity.
• Its disadvantages include being high maintenance, and energy as well as costs.

Solubility of Substances in Water

The dissolution of any substance in water depends on the amount of substance and the volume of water and their properties.

• A solution is said to be saturated if it cannot dissolve more of its substance.
• Larger quantities of salt can be dissolved in water on heating or increasing water volume.
• Water can dissolve different amounts of soluble substances.
• The solubility of water largely depends on the temperature.
• Substances such as salt, sugar, and some proteins are soluble in water.
• Oils, fats, and some organic solvents are not soluble in water. 

Water is the “universal solvent” as it can dissolve more substances than any other liquid.

Conclusion

Separation refers to the segregation of certain substances from a mixture. This process helps in the successful removal of impurities or harmful substances. There are various methods of separation, including hand picking, threshing, winnowing, sedimentation, decantation, filtration, and evaporation. Each of these methods has its own benefits and shortcomings. Solubility refers to the capacity for a substance to dissolve in another. Water is believed to be a universal solvent due to its ability to dissolve more substances than other liquids. Substances such as salt, sugar, and certain proteins are soluble in water while others such as fats and oils are insoluble and also known as hydrophobic. The ability of substances to be soluble depends on factors such as temperature, volume, and their properties.