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1.Why diamond is used as abrasive?
Ans:Diamond is very hard due to net work structure.
2.Why graphite is used as lubricant?
Ans:Graphite cleaves easily between the layers and therefore it is very soft and slippery.
3.Give the difference between diamond and graphite?

Diamond Graphite
  • It ocurs naturally in free state
  • It ocurs naturally as well as manufactured artificially
  • It is transparent and has high refractive index
  • It is black in colour and opaque
  • It is hard
  • It is soft
  • Bad conductor of heat and electricity
  • It is good conductor of electricity
  • Chemical reactivity is low
  • Chemical reactivity high
  • It has three dimensional network structure
  • It has a two dimensional sheet like structure

4.What is the hyprisation of carbon in diamond and graphite?
Ans:In diamond, carbon atom is Sp3 and in graphite it is SP2
5.Why graphite conducts electricity?
Ans:In graphite, carbon atom exin in Sp2 hybridised state, only 3 of the 4 valence electron of carbon participate in bonding which make 3 sigma bonds with three neighbouring carbon atom. The fourth electron form π bond. The π electrons are delocalised over the whole sheet and as they mobile graphite conducts electricity.
6.Define molecular crystals?
Ans:Molecular crystals are those in which particles forming the crystal are polar or non polar molecules which are held by dipole- dipole interaction or Vanderwaal force.
7.What are the different types of molecular crystal?
Ans:(i) Polar molecular crystal
(ii) Non-polar molecular crystal.
8.What is meant by dry ice?
Ans:Solid carbon dioxide is called dry ice.
9.Define the term polymorphism?
Ans:The phenomenon by which substance (compound/element) exist in two or more different crystalline forms is called polymorphism.
10.What is meant by allotropy?
Ans:Different crystalline forms of the same element are called its allotropes or allotropic forms and the phenomenon is called allotropy.

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