SEPARATION OF SUBSTANCES | Study

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PURE SUBSTANCES: The substances which contain only one kind of particles are called pure substances. Elements and compounds are pure substances.

ELEMENT: A substance made from identical particles of one material.

COMPOUND: A substance formed as a result of chemical combination of two or more elements in a fixed ratio.

Solution: A solution is a homogeneous mixture of two substances.

Solvent: The substance in larger quantity is the solvent.

The substance other than the solvent present in the solution is/are is the solute/solutes.

IMPURE SUBSTANCES: The substances which contain more than one kind of particles are called impure substances.

NEED FOR SEPARATING COMPONENT OF A MIXTURE

Removing harmful or unwanted components, and obtaining useful and desire component in pure form.

Methods of separation are Threshing, winnowing, handpicking, sieving, magnetic separation, floating and sinking method, filtration.

separation to immiscible liquids, churning to separate cream from milk, sublimation.

(i) Separation of solid from other solids:

(a) Threshing: The process of separating grain from husk or chaff is called threshing.

Chaff: The waste material of agriculture processes such as pieces of straw are called chaff.

(b) Winnowing: The process of separation of heavier and lighter components of a mixture by wind or blowing air.

(c) Hand-picking: The process of picking the undesirable components from desirable material with hand is called Hand-picking.

(d) Sieving: The process of separating the solid constituents of different sizes in a mixture using a sieve is called sieving.

Sieve: A sieve is a device with many small holes in it , which allow the smaller particles to pass through and stops the bigger particles in it is called a sieve.

(e) Magnetic separation: Process of seperating the magnetic material by moving a magnet over a mixture of magnetic and non-magnetic substances is called magnetic seperation. In this process the magnetic material sticks to the magnet are removed.

(ii) Separation of water soluble solids or separating solute dissolved in solvent:

(a) Evaporation: Process of converting a liquid into its gaseous state by placing in open air without heating is called evaporation.

(b) Condensation: Process of converting a gaseous material into its liquid state by cooling it is called condensation.

(iii) Separation of insoluble solids from Liquids:

(a) Sedimentation: The process of settling down of heavier and insoluble component from mixture is called sedimentation.

Examples: sand, water.

(b) Decantation: The process of transferring clean liquid without disturbing the sediment, is called decantation

(c) Loading: The methods by which finer particles are made to settle faster by dissolving a small quantity of alum.

(d) Filtration: In this process the impurities are passed through a filter.

Filter: The filter has pores in it that allow only liquids to pass through the pores but stops the suspended particles or solid particles.

Therefore, the filter separates the suspended particles or solid particles.

The clear liquid so obtained in filtration is called the filtrate.

residue: The left over material on the filter paper due to filtration is known as residue.

(iv) Separation of Immiscible Liquids:

IMMISCIBLE: The liquids which donot mix well with one another are called immiscible liquids.

Example: Mixture of oil and water are immiscible liquids.

immiscible liquids are sepreated by centrifugation, churning etc. methods.

(b) Centrifugation: The method in which mixture containing suspended particles is rotated at a high speed in a centrifuge and heavier particles settle down.

Example: Cream is separated from milk, using centrifugation method.

(c) Churning: The method which is used for separating lighter particles of solid suspended in.

SEPARATING SOLUTE NOT SOLUBLE IN A SOLVENT

Flotation and sinking methods:- This method is used when the components are not soluble in water and one of the component of a mixture is lighter than water and the other is heavier than water.

SUBLIMATION:- The changing of a solid directly to vapour, without coming to liquid state is called sublimation.

Husk and stones could be separated from grains by handpicking.

· Husk is separated from heavier seeds of grain by winnowing.

· A saturated solution is a solution in which no more solute could be dissolved.

· More of a substance can be dissolved in a solution by heating it.