UPSC

 Synthetic Fibers and Plastics   1.           Synthetic Fibres  

• A synthetic fibre is a chain of small units joined together. Each small unit is actually a chemical substance. Many such small units combine to form a large single unit called a polymer.
• Polymers occur in nature also. Cotton, for example, is a polymer called cellulose. Cellulose is made up of a large number of glucose units.
• Silk fibre obtained from silkworm was discovered in China and was kept as a closely guarded secret for a long time. Attempts were made to make silk artificially. Towards the end of the nineteenth century, scientists were more...

 Solutions, Osmosis, Electro - Chemistry   1.           Solutions  

• 1 part per million (ppm) of fluoride ions in water prevents tooth decay, while \[1.5\]ppm causes the tooth to become mottled and high concentrations of fluoride ions can be poisonous (for example, sodium fluoride is used in rat poison).
• Intravenous injections are always dissolved in water containing salts at particular ionic concentrations that match with blood plasma concentrations and so on.
• Solutions are homogeneous mixtures of two or more than two components. By homogenous mixture we mean that its composition and properties are uniform throughout the mixture. Generally, the component more...

 Hydrogen   1.           Position of Hydrogen in the Periodic Table  

• Hydrogen has the simplest atomic structure among all the elements around us in Nature. In atomic form it consists of only one proton and one electron. However, in elemental form it exists as a diatomic (\[{{H}_{2}}\]) molecule and is called dihydrogen. It forms more compounds than any other element. In the global concern related to energy can be overcome to a great extent by the use of hydrogen as a source of energy.
• Hydrogen has electronic configuration \[1{{s}^{1}}\]. On one hand, its electronic configuration is similar to the outer electronic more...

The s - Block Elements   1.           In Periodic Table  

• The s-block elements of the Periodic Table are those in which the last electron enters the outermost s-orbital. As the s-orbital can accommodate only two electrons, two groups (1 & 2) belong to the s-block of the Periodic Table.
• Group 1 of the Periodic Table consists of the elements: lithium, sodium, potassium, rubidium, caesium and francium. They are collectively known as the alkali metals. These are so called because they form hydroxides on reaction with water which are strongly alkaline in nature.
• The elements of Group 2 include beryllium, magnesium, calcium, strontium, more...

 The p - Block Elements   1.           The Boron Family  

• Boron is a fairly rare element, mainly occurs as orthoboric acid, (\[{{H}_{3}}B{{O}_{3}}\]), borax, \[N{{a}_{2}}{{B}_{4}}{{O}_{7.}}10{{H}_{2}}O\], and kemite, \[N{{a}_{2}}{{B}_{4}}{{O}_{7}}.4{{H}_{2}}O\]. In India borax occurs in Puga Valley (Ladakh) and Sambhar Lake (Rajasthan).
• Aluminium is the most abundant metal and the third most abundant element in the earth's crust (\[8.3\]per cent by mass) after oxygen (\[45.5\]per cent) and Si (\[27.7\]per cent). Bauxite, and cryolite, are the important minerals of aluminium. In India it is found as mica in Madhya Pradesh, Kamataka, Orissa and Jammu.
• Gallium, indium and thallium are less abundant elements in nature.
• more...

 Surface Chemistry   1.           Adsorption and Absorption  

• In adsorption, the substance is concentrated only at the surface and does not penetrate through the surface to the bulk of the adsorbent, while in absorption, the substance is uniformly distributed throughout the bulk of the solid. For example, when a chalk stick is dipped in ink, the surface retains the colour of the ink due to adsorption of coloured molecules while the solvent of the ink goes deeper into the stick due to absorption. On breaking the chalk stick, it is found to be white from inside.
• A distinction can be made between absorption and adsorption more...

 Miscellaneous: Chemistry   1.           Corrosion  

• Corrosion slowly coats the surfaces of metallic objects with oxides or other salts of the metal. The rusting of iron, tarnishing of silver, development of green coating on copper and bronze are some of the examples of corrosion. It causes enormous damage to buildings, bridges, ships and to all objects made of metals especially that of iron. We lose crores of rupees every year on account of corrosion.
• In corrosion, a metal is oxidised by loss of electrons to oxygen and formation of oxides. Corrosion of iron (commonly known as rusting) occurs in presence of water and air. At more...

 THE HARAPPAN CULTURE: BRONZE AGE CIVILIZATION   THE INDUS or the Harappan culture is older than the chalcolithic cultures which have been treated earlier, but it is far more developed than these cultures. It arose in the north-western part of the Indian subcontinent. It is called Harappan because this civilization was discovered first in 1921 at the modern site of Harappa situated in the province of West Punjab in Pakistan. It extended from Jammu in the north to the Naramada estuary in the south, and from the Makran coast of Baluchistan in the west to Meerut in the north-east. The area formed a triangle and accounted for about 1,299,600 square kilometers.        Nearly 1500 Harappan sites are known so far in the subcontinent. Of these, the two most important cities were Harappa in Punjab and Mohenjo-Daro (literally the mound of the more...

 THE LATER VEDIC PHASE   EXPANSION IN THE LATER VEDIC PERIOD (C. 1000-500 B.C.) THE HISTORY of the later Vedic period is based mainly on the Vedic texts which were compiled after the age of the Rig Veda. The collections of the Vedic hymns or mantras were known as the Samhitas. For purposes of recitation, the prayers of the Rig Veda were set to tune, and this modified collection was known as the Sama Veda Samhita. In addition to the Sama Veda. In post-Rig Vedic times two other collections were: composed. These were the Yajur Veda Samhita and the Atharva Veda Samhita. The Yajur Veda contains not only hymns but also rituasis which have to accompany their recitation. The Atharva Veda contains charms and spells to ward off evils and diseases. The Vedic Samhitas were followed by the composition of a series more...

  TERRITORIAL STATES AND THE FIRST MAGADHAN EMPIRE   The Mahajanapadas In the age of the Buddha we find 16 large states called Mahajanapadas, They were mostly Bituated north of the Vindhyas and extended from the north-west frontier to Bihar. Of these Magadha, Koshala, Vatsa and Avanti seem to have been considerably powerful. Beginning from the east we hear of the kingdom of Anga which covered the modern districts of Monghyr and Bhagalpur. It had its capital at Champa, Eventually the kingdom, of Anga was swallowed by its powerful neighbor Magadha.   Magadha embraced the former districts of patna, Gaya and parts of Shahbad, and grew to be the leading state of the time. North of the Ganga in the division of Tirhut was the state of the Vajjis which included eight clans. But the most powerful were more...