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Classification of matter on the basis of chemical composition

Classification of matter  This post tell about  all  information Classification of matter on the basis of chemical composition Classificatio...

Classification of matter 


This post tell about  all  information Classification of matter on the basis of chemical composition


Classification of matter Introduction

The objects around us, including air, water, stones, metals, trees, etc.  , are different varieties of matter.  Anything that occupies some space and has mass is called matter.  The smallest particles of matter which retain all the properties of matter and exist independently are called molecules.  On the basis of the forces of attraction existing between the molecules of a substance, matter can be classified as solids, liquids and gases.  The characteristics of these three states of matter and the interconversion of a substance from one state to the other represent one aspect of the study of matter.  Matter can also be classified on the basis of chemical composition into three major categories, namely, elements, compounds and mixtures.  There are 115 elements discovered till today and these elements are further classified into metals, non-metals and metalloids on the basis of certain characteristic properties.  Study of matter also involves study of the properties of various categories of elements.  It also includes the study of basic differences between compounds and mixtures, and the study of techniques of separation of different types of mixture.  Molecules are the constituent particles of matter and the characteristics of these molecules and their arrangement in the various states of matter were explained by the kinetic molecular theory of matter 


Classification of matter on the basis of chemical composition

Classification of matter on the basis of chemical composition

Pure Substances

Substances which are homogeneous in nature and contain particles (molecules) of only one kind are called pure  substances.  A pure substance is homogeneous in nature and has definite set of properties.  The composition of pure substances cannot be changed by physical methods.  Pure substances can be further classified as elements and compounds.


Elements 

Pure substances in which molecules are composed of only one kind of atoms are called elements.  

Examples: Silver, iron, oxygen, nitrogen, etc.  


Atomicity of an element 

The number of atoms present in the molecule of an element is called its atomicity.  Based on the atomicity, the elements are classified into three types as listed hereunder.  

1. Monoatomic elements: The elements each of whose molecules contain only one atom. 

Examples: Cu, Ag and He 

2. Diatomic elements: The elements each of whose molecules contain two atoms.  

Examples: H2, O2 and N2 

3. Polyatomic elements: The elements each of whose molecules contain more than two atoms.  

Examples: O3, P4 and S8 


Compounds 

Pure substances in which two-or more elements combine chemically in a fixed proportion by weight are called compounds.  

For example, water (H2 O) is considered a pure substance even though it consists of two kinds of atoms, s it has a fixed number of hydrogen and oxygen atoms combined together chemically in a definite proportion by weight.  Hydrogen and oxygen combine in a fixed ratio, 1: 8 by weight, to form water.  


Classification of Elements 


It was found that there was a wide variation in the properties of elements.  Hence, these were further classified into three categories, i, e., Metals, non-metals and metalloids, based on the properties they exhibit.





Metalloids

Metalloids are elements which show the properties of  both metals and non - metals. 

Examples: Germanium, arsenic, antimony, selenium and tellurium 


Uses of Metals 

Iron (Fe) 

1. Iron is mainly used in the form of steel, an alloy in which the major component is iron. 

2. Steel is used for making buckets, drain pipes, chains, etc.  , as it is extremely tough and it can withstand stress and has a high melting point. 


Lead (Pb) 

1. It is used for making containers for corrosive liquids  and protective screens for X - ray and other harmful radiations as it is unaffected by impure water, steam or dilute mineral acids and has a low melting point (337 ° C).  

2. It is used in the automobile batteries. 


Magnesium 

1. It is used in fireworks because it burns with a dazzling white flame.  

2. It is used as a reducing agent in the extraction of metals.


Aluminium 

1. Due to its light weight, it is used for the manufacture of aircrafts and automobiles 

2. It is used to make electric transmission cables.  

3. It is used for making utensils and novelty articles.  


Zinc 

1. It is used for galvanizing iron to protect it from rusting.  

2. It is used as a cathode container in making dry cells.  


Copper 

1. It is used in electric transmission wires and electrical goods.  

2. It is used in electroplating and electrotyping, 

3. It is used for making printed circuit boards and electronic devices.  

4. Copper salts are largely used as insecticides, 


uses of Non - metals 


Oxygen 

1. It helps in the process of respiration and combustion.  

2. It has medical and industrial uses.  


Nitrogen 

1. It dilutes the activity of oxygen in air.  

2. It is used in biological food and biological specimens.  


Sulfur 

1. Sulfur powder is an excellent insecticide and fungicide.  

2. It is used to make the natural rubber hard for making tires.  


Iodine

1. lodides are used in medicine and photography 

2. It is used in the manufacture of tincture of iodine.


Hydrogen 

1. It is an excellent non-polluting fuel.  

2. It is used to fill weather - observation balloons and gas bags for airships.  


Uses of Noble Metals 

Gold 

1. It is used for covering the mainframe of artificial satellites.  

2. It is used for making ornaments and coins.  


Silver 

1.silver is used for making ornaments and coins.


Platinum 

1. It is used as a catalyst in many chemical reactions.  

2. It is used in making jewelry 

Titanium 

1. It is completely inert to human body fluids, making it ideal for medical replacement structures, such as, hip and knee implants.  

2. Titanium forms a very tenacious surface oxide layer which is an outstanding corrosive inhibitor 


mixtures


The systematic study of elements is done by categorizing them as metals, non-metals and metalloids.  The different elements combine with each other to form compounds.  The formation of compounds from elements results in change in the molecular composition.  Two or more substances, either elements or compounds, can be mixed together in any proportion.  The resultant substances are called mixtures.  Since the formation of a mixture involves only physical process, there is no change in the molecular composition.


Classification of a mixture 

among the various types of a mixture, alloys occupy the most significant position in view of the wide range of applications they find in industry as well as in day -  to - day life.


Alloys and their uses 

Alloy is a homogeneous mixture of two or more metals (or a non-metal).  Some important alloys, their composition and uses are listed in the following table:


Separation of a Mixture

In a mixture, the individual components retain their original properties.  This is exploited to separate the mixture into individual components.



Principles Involved 


The difference in one or more of the following physical properties of the constituents is utilized to separate the components of a mixture.  

1. Physical state 

2. Density 

3. Melting and boiling points 

4. Solubility 

5. Magnetic properties 

6. Diffusion 

7. Ability to sublime 

8. Volatility


Separation of kcl from a solution of kcl and water

The KCl solution is taken in a distillation flask (x). 

The flask is carefully heated the solvent evaporates and the water vapor condenses in Liebig's condenser (Y). KCl remains in the distillation flask and the water is collected in the receiver  flask.  


Separation of a Liquid - Liquid Mixture 


(A) Separating funnel 

Principle: Separation of immiscible liquid components using a separating funnel where liquids separate out due to different densities.

Example

Separation of petrol (lighter) from water (heavier).

1. The liquid-liquid  mixture is poured into a separating funnel clamped vertically and the mixture is allowed to stand clear layers of the liquids are formed as the band with higher density settles down at the bottom of the flask.

2. The nozzle tap is opened slowly and the heavier component is  allowed to trickle down.  The lighter component remains in the flask.


(B) Fractional distillation 

principal: Separation of two miscible liquid components using a distillation flask with a fractionating column using the difference in boiling points of the liquid components.

Example: Laboratory separation of methanol from water.  

Procedure 

1. The alcohol - water mixture is poured into a distillation flask and the flask is heated at a temperature which is equal to or more than the boiling point of alcohol but less than that of water.  

2. When the mixture in the flask is subjected to slow heating, alcohol being more volatile than water, gets vaporized first.  As the vapors pass through the fractionating column they get condensed and the liquid formed is collected in the receiver.  Water remains in the distillation flask. 


Separation of a Gas - Gas Mixture

based on the physical properties of gases, different physical methods are adopted 

(A) Diffusion 

Principle Difference in densities of gaseous components.  

Examples: 

CO2and H2 

SO2and N2 

(B) Dissolution in suitable solvents 

Principle.  When one constituent is soluble in a liquid or reacts chemically with a liquid, it is dissolved in that solvent, from which it can be recovered by a chemical reaction.

Examples: 

N2 (insoluble) and CO2 (soluble) in KOH 

NH3 (soluble) and N2 (insoluble) in H2O 

SO2(soluble) and O2(insoluble) in KOH 


(C) Preferential liquefaction 


Principle: Employed  industrially for the separation of a homogeneous mixture of two gases, one of which liquefies under high pressure, when they are allowed to expand suddenly 

Example: A mixture of H2 and NH3 under very high pressure is allowed to expand suddenly.  NH3 is liquefied and gets separated from H2.  


(D) Fractional evaporation 


Principle: This process can be adopted when a mixture of two gases having different boiling points is liquefied by allowing it to expand suddenly under extremely high pressure, followed by evaporating the mixture at the respective boiling points of the constituent gases.  

Examples: N2 and O2 (N2 boils off) 


Separation of a liquid - Gas Mixture 

The solution of a gas in a liquid is called liquid - gas mixture.  

(A) Separation of a liquid - gas mixture by heating 

Principle: The solubility of a gas in a liquid decreases with the rise in temperature.  

Example: 

1. The liquid - gas mixture (eg. Water - CO2) is filled in a flask and heated gently so that the solution does not boil.  

2. On heating, the solubility of the gas decreases and the dissolved gas is developed and collected 


(B) Separation of a liquid - gas mixture by releasing pressure 

Principle: The solubility of a gas in a liquid can be increased by increasing external pressure and  is decreased with the decrease in external pressure 

Example: CO2 gas is dissolved in water by applying pressure in aerated drinks and thus Co2 gas comes out with a fizzing sound when the pressure is released.  


Chromatography 


It is a technique used for the separation and identification of dissolved constituents of a mixture by adsorbing them over an appropriate adsorbent material 

principal: This process is based on the difference in adsorption of constituents by a surface of an appropriate adsorbent material or solid medium (  stationary phase).  The rate of adsorption of a particular constituent depends upon its solubility in the solvent (moving phase) and its affinity for the adsorbing material.

Example: Separation of colored constituent in a mixture of ink by paper chromatography.

Procedure 

1. A spot of ink is placed at the center of a base line on a strip of filter paper.  

2. The spot is dried and the paper is hung in a glass jar with its lower end immersed in solvent 

3. The solvent flows over the spot and carries the components to distances along the paper indicated by color spots, which is characteristic of each constituent  in the mixture.  

The various methods of separation of mixtures find applications in various fields of industry.  

One of the most important applications is in metallurgy where different methods of separation have been employed to remove impurities from the ores.  

Separation techniques, like, distillation and fractional distillation are utilized in the refining of petroleum, alcohol industry, pharmaceutical and food industry, etc.  Solvent extraction is also widely used in the manufacture of medicines, chromatography finds applications in research laboratories for the identification of new compounds.


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Classification of matter on the basis of chemical composition
Classification of matter on the basis of chemical composition