7. Do you know the difference between the words principal and principle? Read the following and answer the question.

These two words, though often confused and used incorrectly and interchangeably, share no common definitions. Generally, it's enough to remember that principal (= chief, primary, most important) is usually an adjective and that principle (= a truth, rule, doctrine, or course of action) is virtually always a noun.

8. Find the suitable definition for each of the terms given.

acetylene; alkene; alkyne;

aromatic; cyclic; diene;

ethylene; fraction; isomer;

naphthalene; naphthene; paraffin;

polynuclear; saturated; unsaturated;

1. A flammable gas (C₂H₂) used in organic chemicals and welding metals.

2. Containing no multiple bonds and thus not undergoing additional reactions.

3. A compound having a molecular structure containing closed ring(s) of atoms.

4. A flammable hydrocarbon gas of the alkene series, occurring in natural gas, and crude oil used in chemical synthesis, esp. in the manufacture of polyethylene.

5. A flammable, waxy solid consisting of a mixture of saturated hydrocarbons, used in candles, cosmetics, polishes, sealing and waterproofing compounds.

6. An unsaturated hydrocarbon having two double bonds between carbon atoms.

7. Any of a group of cyclic aliphatic hydrocarbons (e.g., cyclohexane).

8. Any of the series of unsaturated hydrocarbons containing a double bond, including ethylene and propene with the general formula C_nH_2n.

9. A bicyclic aromatic hydrocarbon with chemical formula C₁₀H₈.

10. Any of the series of unsaturated hydrocarbons containing a triple bond, including acetylene, with the general formula: C_nH_2n-2.

11. Each of the portions into which a mixture may be separated according to a physical property such as boiling point or solubility (растворимость).

12. Each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.

13. Having carbon-carbon double or triple bonds and therefore not containing the greatest possible number of hydrogen atoms for the number of carbons.

14. Compounds containing an unsaturated ring, e.g. benzene and its derivatives.

15. Having polycyclic structure.

9. Explain the ideas expressed in the phrases using the words of your own.

1) with all carbon bonds satisfied; 2) compounds which react readily; 3) hydrocarbon chain carries the full complement; 4) fused double-ring compounds.

10. Read the text again and answer the questions given.

1. What are the general characteristics of the paraffinic series of hydrocarbons?

2. What did you learn about the straight paraffinic molecules?

3. Describe the branch-chained paraffins.

4. What is the specificity of saturated hydrocarbons?

5. Give the general characteristics of aromatics.

6. Give examples of aromatics and comment on their structure.

7. What are naphthenes?

8. How many rings can be present in the nahthenic structure?

9. What are the general characteristics of naphthenes? How do they form?

10. How can diens be described?

11. What is the difference between diens and alkynes?

12. What do alkenes, diens, alkynes have in common?