KENDRIYA VIDYALAYA NO.1 JAIPUR

SCIENCE PROJECT FILE FA – 2 (2015-16)

ON“SEPARATION OF SUBTANCE”

SUBMITTED BY : Hari Om Sharma SUBMITTED TO : Mrs. Neha Jain

WHAT IS SEPARATION ?

In chemistry and chemical engineering, a separation process, or a separation technique, or simply a separation, is a method to achieve any mass transfer phenomenon that converts a mixture of substances into two or more distinct product mixtures (which may be referred to as fractions), at least one of which is enriched in one or more of the mixture's constituents. In some cases, a separation may fully divide the mixture into its pure constituents. Separations are carried out based on differences in chemical properties or physical properties such as size, shape, mass, density, or chemical affinity, between the constituents of a mixture. They are often classified according to the particular differences they use achieve separation .Usually there is only physical movement and no substantial chemical modification . If no single difference can be used to accomplish a desired separation,multiple operations will often . . be performed in combination to achieve the desired end.

TYPES OF SEPARATIONSome types of separations are listed below :-• Crystallization•Filtration•Decantation•Evaporation•Simple distillation•Fractional distillation•Chromatography

CRYSTALLIZATIONIn this ethod of separation , difference in solubility different components in the same solvent is used .  Often, when a solid substance (single compound) is placed in a liquid, it dissolves. Upon adding more of the solid, a point eventually is reached beyond which no further solid dissolves, and the solution is said to be saturated with the solid compound. The concentration of the saturated solution depends on the temperature, in most cases a higher temperature resulting in a higher concentration.

These phenomena can be employed as a means of effecting separation and purification. Thus, if a solution saturated at some temperature is cooled, the dissolved component begins to separate from the solution and continues to do so until the solution again becomes saturated at the lower temperature. Because the solubilities of two solid compounds in a particular solvent generally differ, it often is possible to find conditions such that the solution is saturated with only one of the components of a mixture. When such a solution cools, part of the less soluble substance crystallizes alone, while the more soluble components remain . . dissolved.

FILTRATIONFiltration is commonly the

mechanical or physical operation which is used for

the separation of solids from fluids (liquids or gases) by

interposing a medium through which only the fluid

can pass. The fluid that passes through is called the filtrate. Oversize solids in the

fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles

(depending on the pore size and filter thickness). Filtration is also used to describe some

biological processes, especially in water treatment

and sewage treatment in which 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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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.

EVAPORATION This is good for separating a soluble solid from a liquid (a soluble substance does dissolve, to form a solution).For example copper sulphate crystals can be separated from copper sulphate solution using evaporation. Remember that it is the water that evaporates away, not the solution.

SIMPLE DISTILLATIO

NThis is good for separating a liquid from a solution. For example, water can be separated from salty water by simple distillation. This method works because the water evaporates from the solution, but is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind.

FRACTIONAL DISTILLATIONAL

This is good for separating two or more liquids from each other. For example, ethanol (alcohol) can be separated from a mixture of ethanol and water by fractional distillation. This method works because the two liquids have different boiling points.

CROMATOGRAPHYThis is good for separating dissolved substances that have different colours, such as inks and plant dyes. It works because some of the coloured substances dissolve in the liquid better than others, so they travel further up the paper.