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MATHS TALENT TEST SCORES RELEASED OVERALLS

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ABOUT CORROSION

CORROSION




It is defined as the chemical or electrochemical attack of metals by the environment.

the effects of corrosion by these factors;


  • humidity
  • temperature
  • purity of  metal
  • the physical state of metal
  • nature of ions present in it
  • PH
  • position in electrochemical series
  • relative areas of anode and cathode

electrochemical theory of corrosion;


this theory depends on its electrode potential of metal(anode).if a high electrode metal comes in contact with the low electrode(cathode) potential metal causes the galvanic cell setup.

note: the large corrosion occurs at anodic metal.

the galvanic cells are three types:


composition cell;

in this, both the zinc and copper electrodes are dipped in the same electrolysis solution. 
here the zinc is act as anode and the copper is act as like cathode.the electrons are transferred from anode to cathode.here the anode gets corroded.

stress cell;

These types of cells formed by the drawing, rolling, welding, heat treatment of metals.
stressed areas at the metal act as like an anode causes corrosion.

concentration cell;

this type of cells formed the differential oxygen concentration.poor oxygenated parts act like anodes and causes the corrosion.

RUSTING OF IRON:


  • (Fe2O3xH2O)
  • corrosion of iron is called rusting.

prevention methods for avoiding:

  • using metal high purity
  • alloying
  • protective coating by the metallic or non-metallic or organic.

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THE HISTORY OF PERIODIC TABLE

The periodic table is invented due to avoid confusion while searching and locate the elements. at that time chemists are started to frame ways to group these elements and compounds on the basis of their physical and chemical states. at the beginning of the 18 th century, a scientist called joseph Louis stated that the hydrogen atom is a building material and atoms of all other elements are simply due to a combination of a number of hydrogen atoms. and also considering some examples the atomic weight of hydrogen is taken as ONE. DOBEREINER'S TRIAD THEORY: dobereiner's he was a German man. he was tried to prove the relationship between elements of their properties and atomic weights. he stated that the arrange the three elements are in ascending order which has similar properties with the help of atomic weights. and the middle element is the average of the first and third elements. this theory is called the law of triads. limitations: this law failed for low mass and very high ma...
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THE BLACK HOLE

  A region is an object with such powerful gravity that nothing can shake it, including light. The black hole's mass is concentrated during a point of just about infinite density. this is nothing but singularity. At the singularity, gravity is almost infinitely strong. it crushes normal space-time out of existence. As the distance from the singularity increases, its gravitational influence reduce. At a particular distance, which depends on the singularity's mass, the speed needed to flee from the region equals the speed of sunshine. This distance marks the black hole 'horizon', which is like its surface. Anything that passes through the surface is trapped inside the black hole. Black holes are available several varieties, counting on mass. black holes are formed due to the collapse of large stars at the end of their life cycle. Does OUR SUN BECOME A BLACK HOLE? no, why means read the following data carefully. Our Sun is really too small to finish up as a region. ...
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