Separation of substances

This is a PPT Based on Easy Explanation of the types of Separation of Substances Based on the Chapter of Class 6th Science Chapter CBSE.

1. Separation of Substances There 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.

2. Hand picking Handpicking:   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 .

3. Threshing Threshing:   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 .

4. winnowing Winnowing   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.

5. 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.

6. Evaporation Evaporation   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.

7. Condensation Condensation  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.

8. Sedimentation Sedimentation   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.

9. Decantation Decantation  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 .

10. Filtration Filtration  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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