Available Answers

1. 1.

   Fill in the blank spaces by choosing the correct words from the given list :

   List : allotropy, conductors, graphite, carat, diamonds

   1. Black diamonds are used for cutting and polishing other ___________.
   2. The phenomenon, due to which an element exhibits different physical forms, which have same chemical properties is known as ___________.
   3. The weight of diamond is measured in ___________.
   4. Some fullerenes are super ___________ of electricity.
   5. ___________ is the only crystalline form of carbon which is a good conductor of electricity.
2. 2.

   Statements given below are incorrect. Write the correct statements.

   1. Black diamond is not very hard and is used for making cheap jewellery.
   2. Graphite is good conductor of heat and bad conductor of electricity.
   3. Pure diamond is transparent to visible light, but not to X-rays.
   4. In Buckminsterfullerene, each molecule has sixty atoms arranged in rectangles and triangles.
   5. Graphite is used in nuclear reactors to speed up the excess neutrons.
3. 3.

   Match the statements in Column A, with those in Column B.

   Column A	Column B
   1. A free state of carbon.	(a) Petroleum
   2. A combined state of carbon.	(b) Buckminster fullerene
   3. A form of carbon which is a good conductor of heat and electricity.	(c) Allotropy
   4. A free form of carbon whose one molecule has 60 carbon atoms.	(d) Graphite
   5. Name of various physical form of elements having same chemical properties.	(e) Diamond

    

4. 4.

   Write 'true' or 'false' in front of following statements :

   1. All compounds of carbon are called hydrocarbons.
   2. Carbon is an organogen element.
   3. Diamond is purest form of carbon.
   4. Zinc is found in traces in all plants and animals and hence is an organogen.
   5. Graphite is used as dry lubricant in high speed machinery.
5. 5.

   Tick (√) the most appropriate answer.

   1. When diamond is heated in vacuum for a very long time, it changes into :
      1. graphite
      2. charcoal
      3. lampblack
      4. carbon dioxide
   2. Fullerene molecule [C₆₀] is named after:
      1. H. W. Kroto
      2. R. F. Curl
      3. R. B. Fuller
      4. R. E. Samalley
   3. Graphite is used as a lubricant because it is:
      1. good conductor of heat
      2. good conductor of electricity
      3. very soft and slippery
      4. soluble in oil
   4. The property due to which, the gases and the liquids accumulate on the outer surface of solid is called
      1. adhesion
      2. cohesion
      3. adsorption
      4. absorption
   5. The property due to which an element exhibits various physical forms which has same chemical properties is called.
      1. isotopy
      2. allotropy
      3. atomicity
      4. none of these
6. 6.

   What do you understand by the term organogens? Name four elements which constitute organogens.