Separation of SubstancesThere are many instances when we notice a substance being separated

from a mixture of materials. Tea leaves are separated from the

liquid with a strainer, while preparing tea.

Hand pickingHandpicking: It is the simplest method of separation

of substances. This method is used only when unwanted material is in small quantity. Moreover, shape, size, or color of the unwanted material is different from that of the useful materials. For

example; pebbles, broken grains and insects are separated from rice, wheat and pulses; by

handpicking.

ThreshingThreshing: Threshing is used for separating seeds from the

harvested stalks.Manual Threshing: When the quantity is small, threshing is done manually. Small bundles of the harvested stalks are

thrashed on a hard surface. This helps in separating the grains.Threshing by Animals: For larger quantities, threshing is done

in the traditional way; by using animals. For this, stalks are spread around a pole. Several bullocks are tied to the pole and

are made to walk over the harvested stalks. Trampling by hooves of the animals helps in separating grains.

Threshing Machine: Now-a-days, threshing machines are used for the purpose. It can be powered by either a diesel engine or

an electric motor. It helps in saving time and labour.

winnowingWinnowing is an agricultural method developed by ancient cultures for separating grain from chaff. It is

also used to remove weevils or other pests from stored grain. Threshing, the loosening of grain or seeds from the husks and straw, is the step in the

chaff-removal process that comes before winnowing.

Sieving sieve, or sifter, is a device for separating

wanted elements from unwanted material or for characterizing the particle size distribution

of a sample, typically using a woven screen such as a mesh or net or metal. The word "sift"

derives from "sieve". In cooking, a sifter is used to separate and break up clumps in dry

ingredients such as flour, as well as to aerate and combine them. A strainer is a form of sieve

used to separate solids from liquid.

EvaporationEvaporation is a type of vaporization of a liquid that

occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating

substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor

forming in the liquid phase. Steam produced in a boiler is another example of evaporation occurring in

a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, as commonly observed with ice at or below freezing

or moth crystals (naphthalene or paradichlorobenzene), is called sublimation.

CondensationCondensation is the change of the physical state of matter from gas phase into liquid phase, and is the

reverse of evaporation. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapour to liquid water when in

contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the gaseous phase into

the solid phase directly, the change is called deposition.

SedimentationSedimentation is the tendency

for particles in suspension to settle out of the fluid in which they are entrained and come to rest against a

barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can

be due to gravity, centrifugal acceleration, or electromagnetism. In geology, sedimentation is often

used as the opposite of erosion, i.e., the terminal end of sediment transport. In that sense, it includes the

termination of transport by siltation or true bed load transport. Settling is the falling of suspended particles

through the liquid, whereas sedimentation is the termination of the settling process.

DecantationDecantation is a process for the separation of

mixtures, by removing a layer of liquid, generally one from which a precipitate has settled. The purpose may

be either to produce a clean decant, or to remove undesired liquid from the precipitate (or other layers).

If the aim is to produce a clean solution, a small amount of solution must generally be left in the

container, and care must be taken to prevent any precipitate from flowing with the solution out of the

container.

FiltrationFiltration is any of various mechanical, physical or biological

operations that separate solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass. The fluid that passes through is called the filtrate. In physical filters oversize

solids in the fluid are retained and in biological filters particulates are trapped and ingested and metabolites are retained and removed.

However, the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on

the pore size, filter thickness and biological activity). Filtration occurs both in nature and in engineered systems; there

are biologic, geologic, and industrial forms. For example, in animals (including humans), renal filtration removes wastes from

the blood, and in water treatment and sewage treatment, undesirable constituents are removed by absorption into a biological

film grown on or in the filter medium, as in slow sand filtration.

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