8th Chemistry Carbon and its compound

    

 class 8th science

ICSE/ CBSE Notes-

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8th Chemistry

Carbon and its compound 

Introduction of carbon-



  • Carbon is a solid nonmetal , the symbol of carbon is  'C'
  • The atomic number of carbon is  6 and its mass number is 12
  • Electronic configuration of  carbon is 2,6 



  • Carbon has valence cell 'L' valence electron is 4 and its valency is also 4.
  • Carbon is placed in period 2 and its atomicity is one
  • Carbon link with other carbon atoms and forms along chain ,it is called catenation of the carbon,it is unique property of carbon. it is studied under the separate branch of chemistry called Organic chemistry



  • Compound which contain only carbon and hydrogen are called Hydrocarbon  compounds.



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Occurrence of Carbon-

  • Carbon can occur in both state free and combined.
  • In free state carbon  occur as Diamond, coal, Graphite coke  etc
  • In combined state carbon occur as fats , carbohydrates,proteins ,carbonates ,CNG,LPG etc
  • Carbon also found inside the living organisms like plant ,animals,human being etc







Allotropy

The property of an elements is called allotropy if any atom exist in more than one forms in the same physical states.and each forms of the element is called allotrope of the element.














1-Crystalline forms

In this form the carbon atoms are arranged in a systematic manner .eg Diamond ,graphite etc





Diamond








Graphite

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2 Non crystalline or Amorphous form

In this form the carbon atoms are not arranged in any systematic manner ,they are arranged in irregular manner . eg  coal, charcoal , lamp black etc



coke

coal










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 Difference between  crystalline forms and Non crystalline forms-





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Types of Crystalline forms-

1-Diamond

  • Diamond are found from the mines of Panna in Madhya Pradesh and Golconda in Telengana
  • Diamond are found in  U.S.A ,South Africa, Russia, Brazil.
  • South Africa is the largest producer of diamond in the word.
  • Diamond is formed by molten magma.
  • Diamond is the purest crystalline form of the carbon.




Diamond




  • In the structure of Diamond each CARBON atom lie at the four corners of tetrahedron.
  • Due to tetrahedron arrangement  carbon atom makes rigid and hard structure.









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Properties of Diamond

  • Diamond is the hardest substance which occur naturally.
  • It is represented by symbol  'C'
  • It is transparent and shining in light .
  • It has very high Melting point , because carbon atoms are joined together by strong bond.
  • It is poor conductor of heat and Electricity.
  • It has very high density due to close packing of carbon atom, density is 3.5 g/cm3





Use of  Diamond

  • It is used as a glass cutter for cutting the glass sheets.
  • It is used for making Jewellery.
  • It is use for making the high accuracy thermometer.
  • It is used for protective windows in spacecrafts

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2-Graphite

Graphite is soft ,Dark and Greasy solid ,it is made  by carbon atom.

  • It is represented by symbol  'C'  because it is made of only carbon atom
  • Carbon atoms are arranged in parallel layer which can slide over each other.
  • Carbon atoms are arranged in Hexagons .
  • Each carbon atom is bonded with  three other carbon atoms. 


Graphite


Physical Properties of  Graphite

  • Graphite is dark gray solid having a metallic luster.
  • Graphite has density 2.25  g/cm3 which is lower than diamond.
  • Graphite is a good conductor of heat and electricity.
  • Graphite is insoluble in ordinary solvent.
  • Graphite has high  melting point 3700*c




Use of Graphite
  • Graphite is used as a pencil lead
  • Graphite is used as a lubricant.
  • Graphite is used  for making electrodes.
  • Graphite is used for making crucibles (special pot)


Fullerenes
  • fullerene, also called buckminsterfullerene, any of a series of hollow carbon molecules that form either a closed cage (“buckyballs”) or a cylinder (carbon “nanotubes”).


  • The C60 molecule was named buckminsterfullerene

  • 60 carbon atoms (C60) joined together by single and double bonds to form a hollow sphere 




  • The actual chemical name of  fullerenes is spheroidal carbon cage molecule.
  • It formed by double covalent bond.
  • Its name is C60
  • It is bad conductor of electricity.
  • It do not offer any resistance to electric current. 





2

Amorphous Form of Carbon

There are various form of amorphous form of carbon
  • Charcoal
  • Coke
  • Coal
  • Lamp black 






Charcoal

Charcoal is formed by heating of organic compound in controlled supply of air. which leaves grey porous residue.

  • Charcoal obtained from any organic solid substance of plant or animals.
  • There are three types of Charcoal which obtain from wood,sugar ,bones of animals.



Wood Charcoal
  • Wood Charcoal is noncrystalline or amorphous from of carbon.
  • Wood Charcoal is not occur naturally.
  • Wood Charcoal is prepared by piling logs of wood leaving the a gap in the center and few holes are left at the bottom of the pile.

  • Wood Charcoal is prepared when the fire dies out.


wood charcoal

Note- Activated charcoal
  • Charcoal is made from wood .
  •  Activated charcoal is made by heating charcoal at 900*C in the presence of a gas. 
  • This process causes the charcoal to develop lots of internal spaces or pores. 
  • These pores help activated charcoal trap chemicals.
  • Activated charcoal is commonly used to treat poisoning.
  •  It is also used for high cholesterol and upset stomach.
  • Activation of charcoal increase the adsorption capacity about 100 times of its volume.



Physical Properties of Wood Charcoal

  • Wood Charcoal  grey brittle solid and porous in nature.
  • Its density is 1.5 g/cm3
  • Wood Charcoal float in water because it contain large amount of air in its pores.
  • If Wood Charcoal is boiled then it  sink in water because air split out from the charcoal.
  • Wood Charcoal is bad conductor of heat and electricity.
  • Wood Charcoal adsorbs gases ,liquids and solids.

Chemical Properties of Wood Charcoal

  1. Action with air or oxygen-
when wood charcoal is heated  in air , burns without flame at 400*C it forms carbon dioxide

wood charcoal  +  oxygen  →  carbon dioxide  + Heat


If the supply of air is limited  ,it forms a poisonous gas carbon monoxide






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