Based on the text structure that you identified in part B, what is the author’s purpose for writing the text? Support your answer by listing the main idea of each paragraph. Paragraph 1: Main Idea:

Paragraph 2: Main Idea:

Paragraph 3: Main Idea:

Paragraph 4: Main Idea:

Author’s Purpose:

Text:We now enter for a while the realm of organic chemistry. Organic chemistry is a branch of knowledge which is of supreme interest, since it covers the matters of which our own bodies are constructed, the foods which we eat and the beverages which we drink, besides a host of other things of great value to us.

Although the old division of chemistry into inorganic and organic is still kept up as a matter of convenience, the old boundaries between the two have been eliminated. The distinction arose from the fact that there used to be (and are still to a very great extent) a number of highly complex substances the composition of which is known, for they can be analyzed, or taken to pieces, but which the wit of man has failed to put together. Consequently, these substances could only be obtained from organic bodies. The living trees, or animals, could in some mysterious way bring these combinations about, but man could not. The molecules of these substances are much more complicated than those with which the inorganic chemist deals. The important ingredient in them all is carbon. In addition, hydrogen, nitrogen and oxygen almost completes the list of the simple elements of which these marvelous substances are compounded. In some cases, there appear to be hundreds of atoms in the molecule.

If one takes a glance at a textbook on organic chemistry, the pages are seen to be sprinkled all over with Cs and Os, Ns and Hs. There is an occasional symbol for some other element.

Another feature of this branch which cannot fail to strike the casual observer is the odd names which many of the substances possess. Trimethylaniline, triphenylmethane and mononitrophenol are a few examples which happen to occur to the memory. They are by no means the longest or oddest sounding.

Another peculiarity about these organic substances is that a number of them, each quite different from the others, can be formed of the same atoms. Certain atoms of hydrogen, sulphur and oxygen form sulphuric acid. Under whatever conditions they combine, they never form anything else. On the other hand, there are sixty-six different substances all formed of eight of carbon, twelve of hydrogen and four of oxygen. This can only mean that in such cases as the latter, the atoms have different groupings. When grouped in one way, they form one thing. In another way, some other thing, and so on. This explains the extreme difficulty which the chemist finds in building up some of these organic substances.