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  Elasticity and Plasticity   The property of the body to regain its original configuration (length, or shape) when the deforming forces are removed is called elasticity. On the other hand, if the body does not have any tendency to regain its original configuration on removal of deforming force the body is called plastic body and this property is called plasticity.

• Perfectly elastic body: A body which regains its original configuration immediately and completely after the removal of deforming force from it, is called perfectly elastic body. Quartz and phosphor bronze, are closed to perfectly plastic body.
• Perfectly plastic body: A body which does not regain its original configuration at all on the removal of deforming force, however small the deforming force may be is called perfectly plastic body. Putty mid mud are closed to perfectly plastic body.
• Stress

The internal restoring force acting per unit area of a body is called stress. i.e., Stress = Restoring force/Area

• Strain

The ratio of change in configuration to the original configuration is called strain.  \[strain=\frac{Change\,in\,\,configuration}{Original\,Configuration}\] Strain being the ratio of two like quantities has no units and dimensions.

• Elastic Limit

Elastic limit is the upper limit of deforming force up to which, if deforming force is removed, the body regains its original form completely and beyond which, if deforming force is increased, the body loses its property of elasticity and gets permanently deformed.   Hooke's low   It states that within the elastic limit stress is directly proportional to strain. i.e.. Stress \[\propto \]strain or  Stress =\[E\times \] strain Stress  or  \[\frac{Stress}{strain}=E=Cons\tan t\] Here E is the coefficient of proportionality and is called modulus of elasticity or coefficient of elasticity of a body:  

• Materials-Ductile, Brittle and Elastomers

(i) Ductile materials: The materials which have large range of plastic extension are called ductile materials. They can be drawn into thin wires, e.g., copper, silver, aluminium, iron, etc. (ii) Brittle materials: The materials which have very small range of plastic extension are called brittle materials. These materials break as soon as the stress is increased beyond the elastic limit, e.g., glass, ceramics, cast iron, etc. (iii) Elastomers: The materials which can be stretched to large values of strain are called elastomers. e.g., rubber, elastic tissue of aorta, etc.

• Young's modulus of elasticity (Y): It is defined as the ratio of normal stress to the longitudinal strain within the elastic limit. Thus, \[Y=\frac{Normal\,Stress}{Longitudinal\,Strain}\] or, \[Y=\frac{F/\pi {{r}^{2}}}{\Delta l/{{L}_{0}}}=\frac{Mg{{L}_{0}}}{\pi {{r}^{2}}\Delta l}\]

  Thermal Stress   When a rod is rigidly fixed at its two ends and its temperature is changed, then a thermal stress is set up in the rod. And the corresponding strain developed is called thermal strain, Thermal stress \[=\frac{Force}{Area\,\,of\,\,cross\,\,\sec tion}=\frac{F}{A}=Y\alpha \Delta \theta \] Area of cross section   A where \[\alpha \] = coefficient of linear expansion of the rod \[\Delta \theta \] = change in temperature.                                more...

  Introduction  

• The pollutants may be inorganic, biological or radiological in nature.

(i) Bio-degradable pollutants are domestic wastes which are rapidly decomposed by micro-organisms. (ii) Non-biodegradable pollutants include chemicals, mercuric salts, lead compounds, pesticides, etc. (iii) Natural pollution is caused by radioactive substances, volcanic eruptions, forests and mines fires floods, etc. (iv) Artificial pollution is caused by industries, thermal plants, automobile, exhausts, sewage, etc.   Environment  

• Environment: The conditions existing around animal or human life.

Atmosphere: The gaseous envelop surrounding the earth. It has been classified into following regions:- (i) Stratosphere: The layer of the earth's atmosphere above the troposphere and below the mesosphere. (ii) Troposphere: The lowest region of the atmosphere extending from earth's surface to the lower boundary of the stratosphere. In this region, human beings along with other organisms live. It contains water vapour and is greatly affected by air pollution. Note: The other two layers are Thermosphere and Mesosphere.   Air pollution  

• Air pollution: The major air pollutants are

(i) Carbon monoxide (CO): It is produced by incomplete combustion of gasoline in motor vehicles, wood, coal, inceneration and forest fires. It is treacherous and deadly poisonous gas. It induces headache, visual difficulty coma and death. It blocks the normal transport of oxygen from the lungs to other parts of the body. (ii) Sulphur dioxide\[(S{{O}_{2}})\]: It is produced by petrol combustion, coal combustion, and petrol refining and smelting operations. It hinders the movement of air in and out of lungs. It is particularly poisonous to trees causing chlorosis and dwarfing. In presence of air it is oxidised to \[S{{O}_{3}}\] which is also irritant.             \[2S{{O}_{2}}+{{O}_{2}}(air)\to 2S{{O}_{3}}\] In presence of moisture \[S{{O}_{3}}\] is converted into highly corrosive sulphuric acid.             \[S{{O}_{3}}+{{H}_{2}}O(moisture)\to {{H}_{2}}S{{O}_{4}}\] It attacks marble, limestone, vegetation, paper and textiles and injurious to human beings. (iii) Oxides of nitrogen: \[N{{O}_{2}}\] and NO, Source - combustion of coal, gasoline, natural gas, petroleum refining, chemical plants, manufacturing explosives and fertilizers, tobacco smoke. Breathing \[N{{O}_{2}}\] causes chlorosis to plants and chronic lung conditions leading to death. \[N{{O}_{2}}\] reacts with moisture to form acids.             \[2N{{O}_{2}}+{{H}_{2}}O\to HN{{O}_{2}}+HN{{O}_{3}}\],             \[3HN{{O}_{2}}\to 2NO+HN{{O}_{3}}+{{H}_{2}}O\] (iv) Smoke, dust: Sources: cement works, iron and steel works, gas works, power generating stations. Smog: It is a mixture of smoke and fog in suspended droplet form. It is of two types:

• London smog or classical smog: It is coal smoke plus fog. The fog part is mainly \[S{{O}_{2}}\] and \[S{{O}_{3}}\].It has sulphuric acid aerosol. It causes bronchial irritation and acid rain. It is reducing in nature.
• Photochemical smog or Los Angeles smog: The oxidised hydrocarbons and ozone in presence of humidity cause photochemical smog. Hydrocarbons \[+{{O}_{2}}\], \[N{{O}_{2}}\] NO, O, \[{{O}_{3}}\] \[\to \] Peroxides, formaldehyde, peroxyacetylnitrate (PAN), acrolein etc. It is oxidising in nature and causes irritation to eyes, lungs, nose, and asthamatic attack and damage plants.

Acid rain: The oxides of C, N and S present in the atmosphere, more...

  Introduction  

• Definition

Chemistry is a branch of science which deals with study of matter and various changes it undergoes. It deals with the preparation, properties, reactions and structures of chemical elements and compounds. For convenience the study of chemistry is sub-divided into various branches such as: (i) Inorganic chemistry                 (ii) Organic chemistry                   (iii) Physical chemistry                 (iv) Analytical chemistry              (v) Industrial chemistry

• Valency

During the formation of molecules of compounds, atoms combine in certain fixed proportions. This is because of the fact that different atoms have different combining capacities. The combining capacity of an atom or radical is known as its valency.

• Ions or radicals

In addition to atoms and molecules, a third type of particles occurs in substances. These particles, called ions, or atoms or group of atoms that carry an electrical charge. An ion is formed when electrons are removed from or added to an atoms or group of atoms. When electrons is/are removed the resulting ion is called a cation or basic radical. A cation is positively charged ion. (e.g\[N{{a}^{+}}\]. When electron is/are added the resulting ion is called an anion or acidic radicals. An anion is negatively charged ion e.g.,\[(C{{l}^{-}},O_{2}^{2-})\]An ion or radical is classified as monovalent, divalent, trivalent or tetravalent when the number of charges over it is 1,2,3 or 4 respectively.

• Formula of Elements and Compounds

Formula of dements: The molecule of an element is denoted by writing the symbol of the element and, to the right and below it, a number expressing the number of atoms in the molecule. Formula of compound: A molecule of a compound maybe made up of atom of different elements linked up together chemically and in definite proportion by weight.

• Chemical formula: It is of two types:

(i) Molecular formulae: Chemical formulae that indicate the actual number and type of atoms in a molecule is called molecular formulae. (ii) Empirical formulae: Chemical formulae that indicate only the relative number of atoms of each type in a molecule is called empirical formulae.

• Equivalent weight

(i) Equivalent weight of element \[=\frac{Atomic\,\,weight\,\,of\,\,element}{Valency\,\,of\,\,element}\] (ii) Eq. wt of an acid/base\[=\frac{Molecular\,\,mass}{Basicity\,\,of\,\,acid/Acidity\,\,of\,\,base}\] (iii) Eq. wt of salts\[=\frac{Formula\,\,mass}{(Valency\,\,of\,\,cation)(No.of\,\,cations)}\]

• Expression of strength /concentration of Solution

(i) Mass percent = \[\frac{Weight\,\,of\,\,solute(gm)}{Weight\,\,of\,\,solution(gm)}\times 100\] (ii) Normality \[=\frac{numer\,\,of\,\,gram\,\,equivalents\,\,of\,solute}{Volume\,\,of\,solution\,(lit.)}\] (iii) Molarity =\[\frac{Number\,\,of\,\,gram\,\,moles\,\,of\,\,solute}{Volume\,\,of\,\,solution(lit.)}\] (iv) Molality \[=\frac{Gram\,\,moes\,\,of\,\,solute}{weight\,\,of\,\,solent\,(kg)}\] (v) Mole fraction:  Mole fraction of solute \[={{X}_{A}}=\frac{{{n}_{A}}}{{{n}_{A}}+{{n}_{B}}}\]                           Mole fraction of solvent \[={{X}_{B}}=\frac{{{n}_{B}}}{{{n}_{A}}+{{n}_{B}}}\]                                                             \[{{X}_{A}}+{{X}_{B}}=1\]

• Chemical reaction: The process in which a substance undergoes change to produce new substances with new properties are known as chemical reaction. For example magnesium carbonate when heated produces magnesium oxide and carbon dioxide (i.e. new substances with new properties). A chemical change is generally accompanied by a change of state, change of colour, evolution of a gas or change of temperature etc.
• Chemical equation: The qualitative representation of a chemical reaction in a short hand or concise form in term of symbols and formulae, is called a chemical equation.
• Skeletal chemical more...

  Introduction Chemistry has helped significantly in meeting human needs by providing chemical fertilizers, improved varieties of insecticides and pesticides to increase the yield of crops and fruits. It has given us a large number of lifesaving drugs. Also chemical industries manufacturing polymers, soaps, detergents, glass, ceramics etc.   Industrially Important Compounds Glass   It consists of a mixture of two or more silicates.

• Preparation of glass:
• Common glass (or soft glass): It is used to make bottles, glass wares etc. and is obtained by heating together silica (in the form of sand), sodium carbonate or sodium sulphate and chalk or lime stone (calcium carbonate). Some broken glass and a little coke are usually added. The glass so prepared consists of silicates of sodium and calcium.

\[N{{a}_{2}}C{{O}_{3}}(s)+\underset{\left( silica \right)}{\mathop{Si{{O}_{2}}(s)}}\,\to N{{a}_{2}}Si{{O}_{3}}(s)+C{{O}_{2}}(g)\] \[N{{a}_{2}}S{{O}_{4}}(s)+Si{{O}_{2}}(s)\to N{{a}_{2}}Si{{O}_{3}}(s)+S{{O}_{3}}(g)\] \[CaC{{O}_{3}}(s)+Si{{O}_{2}}(s)\to CaSi{{O}_{3}}(s)+C{{O}_{2}}(g)\]

• Hard glass: For preparation of hard glass \[{{K}_{2}}C{{O}_{3}}\] is used in place of\[N{{a}_{2}}C{{O}_{3}}\]. It consists of a mixture of calcium and potassium silicates.
• Physical properties of glass: Hard, rigid, high viscosity, bad conductor of heat and electricity, brittle, etc.
• Blowing: It is a method to cast the molten glass into different moulds. There are two different methods of glass blowing (i) Free blowing and (ii) Mould blowing
• Free blowing: It involves the blowing of air to inflate the molten glass which is gathered at one end of the blow pipe to give the desired shape.
• Mould blowing: This method was developed after' the technique of free blowing. In this method, molten glass is inflated into a wooden or metal carved mould with the help of blow pipe which gives the molten glass the shape and design of the interior of the mould.
• Chemical properties of glass

(i) It is resistant to action of air and acids except hydroflouric acid. (ii) It is alkaline in nature. (iii) It slowly reacts with water to form alkaline solution.

• Types of Glass

(i) Silica glass: For this type of glass the raw material used is 100% pure form of quartz. It is quite expensive. It is used in the manufacture of laboratory apparatus. It has low thermal expansion. Its softening point is very high and it is resistant to a wide variety of chemicals. (ii) Alkali silicate glass: For it the raw materials used are sand and soda. It is also called water glass because it is soluble in water and used only as a solution. It is generally used to make gums and adhesives. (iii) Lead glass: For this type of glass lead oxide is added to ordinary glass. The addition of lead oxide increases the density and also the refractive index. This type of glass is used for the manufacture of ornamental glass ware, decorative articles etc. (iv) Optical glass: This type of glass is used in the manufacture of optical instruments like binoculars, spectacles, lenses, prisons, telescopes, microscopes etc. It is transparent and can be grounded into the required more...

  General Organic Chemistry  

• Wohler prepared the first organic compound urea while preparing ammonium cyanate.
• Classification of organic compounds:

  The existence of two or more chemical compounds with the same molecular formula but having different properties owing to different arrangement of atoms within the molecule is termed as isomerism

• Hydrocarbons: All those compounds which contain just carbon and hydrogen are called hydrocarbons.
• Functional group: The atom or group of atoms which determine the properties of a compound is known as functional group. e.g. \[-OH\] (alcohol), -CHO (aldehyde), > C = C < (alkene), \[-C\equiv C-\] (alkyne), etc.
• Homologous Series: A series of compounds in which the same functional group substitute’s hydrogen in a carbon chain is called a homologous series, e.g. \[C{{H}_{3}}Cl\] .and \[{{C}_{2}}{{H}_{5}}Cl\] differ by a \[-C{{H}_{2}}\] unit.
• Nomenclature: Chemists developed a set of rules, for naming organic compounds based on their structures which is known as IUPAC rules. The IUPAC name of an organic compounds consists of three parts.

Prefix - word root - Suffix Word root: A word root indicates the nature of basic carbon skeleton.

• In case a functional group is present, it is indicated in the name of the compound with either as a prefix or as suffix.
• While adding the suffix to the word root the terminal 'e' of carbon chain is removed
• If the carbon chain is unsaturated then the final 'ane' in the name of the carbon chain is substituted by 'ene' or ‘yne’ respectively for double and triple bonds.

 

Functional group	Prefix/Suffix	Functional group	Example	IUPAC Name
1. Halogen	Chloro, bromo, lodo	-Cl,-Br,-I	more... Catgeory: Railways Diversity in Living Organisms   Introduction ² Biodiversity refers number and types of wide variety of plants and animals present on earth. In 1773, Swedish botanist Carolus Linnaeus formulated the system of Binomial Nomenclature in his book 'Species plantarum''. In binomial system, each name is expressed in two parts i.e., generic name and specific name. Taxon is the branch of biology that deals with the framing of laws and principles for classifying the organisms on the basis of their characteristics and evolutionary relationships. The hierarchial system of classification was introduced by Kingdom \[\to \] Phylum or Division\[\to \] Class\[\to \] Order\[\to \]Family\[\to \] Genus\[\to \]Species Species is defined as "the smallest real basic unit of taxonomy which is reproductively isolated from other group of individuals". Genus is a group of closely related species that are alike in broad features of their organization. Family is a group of related genera having several common characters. Generally, Order and other higher taxonomic categories are identified based on the aggregates of characters. A Class is made of one or more related orders. The term Phylum is used for animals while Division is commonly employed for plants. Kingdom is the highest taxonomic category. All plants are included in Kingdom Plantae. All animals are included in Kingdom Animalia. Herbarium is a collection of pressed and dried plant specimens that are preserved on paper sheets. In Botanical garden, various plants groups are grown for scientific study, conservation, public education, aesthetics, and recreation. The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and National Botanical Research Institute, Lucknow (India). Museum is a building used for the preservation, storage and exhibition of inanimate objects. Zoological park or zoological garden or zoo is a place where wild animals are kept in protected environment under human care. These animals are kept for public exhibition.   History of Classification Biological classification was first proposed by Aristotle who used simple morphological characters to classify plants and animals. Linnaeus initially separated plants and animals in two Kingdoms i.e., Kingdom Plantae and Kingdom Animalia. Most accepted System of classification is five system classification which was given by Whittaker.   Basic Feature of Whittaker’s Five Kingdoms more... Catgeory: Railways Current Affairs Categories National International Agreements Appointments Government Schemes Summits Awards & Honours Business Economy & Banking Defense Sports Ranks & Reports Important Days Persons Science & Technology State Environment Bills & Acts Schemes Miscellaneous Archive August 2020(12) February 2020(218) January 2020(208) July 2020(35) June 2020(150) March 2020(99) May 2020(42) April 2019(263) August 2019(333) December 2019(336) February 2019(274) January 2019(299) July 2019(356) June 2019(226) March 2019(261) May 2019(262) November 2019(226) October 2019(230) September 2019(317) April 2018(296) August 2018(291) December 2018(302) July 2018(309) June 2018(312) May 2018(322) November 2018(284) October 2018(276) September 2018(272) Trending Current Affairs Pakistan Hosts SCO Anti-Terror Meeting Nepal, 1st Country In South-East Asia To Eliminate Trachoma: WHO SIDBI To Extend Direct Funding Facility To VLEs In CSCs NITI Aayog, ABB India Sign Pact To Benefit India From AI, Robotics PM Of Netherlands Inaugurates Indo-Dutch Ganga Forum Netherlands Becomes 64th Signatory Member Of International Solar Alliance Barbados Elects Mia Mottley As 1st Female Prime Minister Airtel Payments Bank Appoints Anubrata Biswas As MD And CEO Mission Innovation Ministerial Meeting Held In Sweden Prime Minister Modi Chairs 26th Pragati Interaction Please Wait you are being redirected.... You need to login to perform this action. You will be redirected in 3 sec × Reset Password. Email : Send Password Cancel Add Mobile Enter Mobile Number Submit Logout Enter OTP OTP has been sent to your mobile number and is valid for one hour Enter One Time Password Submit Change Mobile: Submit Logout Mobile Number Verified Your mobile number is verified. Close Free Videos × For free video lectures fill in the form below and we will get back to you. * Email Address: * Mobile Number: Submit Cancel   Kingdom Cellular Organization Movement