Distinguish Between. - Science STD 9 Questions - Vidyadip

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Distinguish Between.

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Question 13 Marks

Crystalline and non-crystalline forms of carbon.

Answer

Crystalline forms of carbon	Non-crystalline forms of carbon
(i) A crystalline form has a regular and definite arrangement of atoms.(ii) They have high melting points and boiling points.(iii) A crystalline form has a definite geometrical shape, sharp edges and plane surfaces.(iv) Diamond, graphite and fullerene are different crystalline forms of carbon.	(i) A non-crystalline form does not have a regular and definite arrangement of atoms.(ii) They have low melting points and boiling points.(iii) They are amorphous, hence, they do not have definite geometrical shape.(iv) Coal, charcoal and coke are different noncrystalline/amorphous forms of carbon.

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Question 23 Marks

Diamond and graphite.

Answer

Diamond	Graphite
(i) Diamond is a brilliant, hard and crystalline allotrope of carbon.	(i) Graphite is a black, soft, brittle and slippery crystalline allotrope of carbon.
(ii) In diamonds, every carbon atom is bonded to four neighbouring atoms by covalent bonds forming tetragonal three dimensional structure which makes it very hard.	(ii) In graphite, every carbon atom is bonded to three other carbon atoms by covalent bonds in such a way that a hexagonal layered structure is formed. A graphite crystal is made of many such layers of carbon atoms. These layers slip over each other on applying pressure.
(iii) Density of diamond is 3.5 g/cm3.	(iii) Density of graphite is 1.9 to 2.3 g/cm3.
(iv) Diamond is a bad conductor of electricity as it does not have free electrons.	(iv) Inside each layer of graphite, free electrons move continuously within the entire layer. Hence, graphite is a good conductor of electricity.

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