М. М. Кутепова The World of Chemistry Мир

Listen to the dialogue again and write down all the expressions of incomprehension that Dolly uses. Translate them into Russian.

Using these expressions ask your partner die following questions and let him/her give you the answers.

Example: What compounds belong to the class called hydrocarbons?
I can't understand what compounds belong to the class called hydrocarbons.

1. 
   What is the formula of glucose?
   
2. 
   What is the structure of an inorganic compound?
   
3. 
   What is the process of forming petroleum from other liquid fraction?
   
4. 
   How is calcium carbonate converted into calcium oxide?
   
5. 
   Why is pure water a poor conductor of electricity?
   
6. 
   How can carbon dioxide be removed from dioxide/nitrogen mixture?
   
7. 
   What class of organic compounds do principle components of petroleum belong to?
   
8. 
   Why is the study of organic chemistry a part of general chemistry?
   

13. 
    Read another text on carbon and say which information corresponds to the ideas expressed in the first text and the dialogue and which does not?
    

CARBON
Carbon is to be ranked along with hydrogen and oxygen as one of the most important of all the elements to man. Carbon occurs in nature as a free element and in many compounds. It constitutes only about 0.03 percent of the Earth’s crust, but this relatively small amount of the element is of great importance. Its importance is indicated by the 300,000 or more compounds of the element which exist naturally or which have been prepared. It is proved that this number is approximately ten times the number of compounds of all the other elements put together. For a long time it was believed that these compounds might have never been produced except with the aid of organic life, in other words, by living plants and animals. For this reason they were called organic compounds. It is known that carbon occurs in two crystalline forms which differ strikingly by their properties. Graphite is black, soft, a good conductor of electricity. Diamond, on the contrary,


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is colourless and transparent, the hardest of known substances, a non-conductor of electricity. It is the crystal structure, as determined by X-rays, which gives an explanation of this contrast of properties. The four valence electrons of each carbon atom enable it, by sharing electrons with four of its neighbours, to be linked with them in a covalent union. It may be shown by X-rays examination that in the diamond the four nearest neighbours of each carbon atom are symmetrically arranged about it in space. All atoms in a diamond are thus firmly linked together, hence the whole crystal acts as a giant molecule. Thus we account for the extreme hardness of the diamond, its high melting point, and its failure to dissolve in any solvent. On the other hand, it is found that graphite possesses parallel planes of atoms, and each is at a considerable distance from its neighbours. Each carbon atom in graphite has three nearest neighbours and they all are present in its own plane. Only three of the four valence electrons of each atom are needed for furnishing bonds with these nearest neighbours and the fourth is available for producing a bond with a neighbouring plane. A certain portion of the electrons in graphite are relatively free to move as it is true of metals. Hence, graphite is a conductor of electricity

14.