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III. Read and translate the text




CHEMICAL COMPOUNDS

There are three big classes of chemical compounds: acids, bases and salts. What are acids? In Latin, the word meaning "sharp" is acidits. Think of the acute mouth sensation that the mention of rhubarb, lemon juice and vinegar produces and you will understand the derivation of the word. These substances are "sharp" or sour.

Acetic acid is present in vinegar; ants' stings and stinging nettles contain formic acid; citric acid is one of the substances found in citrus fruits such as lemon; grape juice includes tartaric acid; sour milk presents us lactic acid; green apples are rich with malic acid; sour taste of rhubarb and spinach is stipulated by oxalic acid. Finally, in our stomach, hydrochloric acid provides digestion.

In the laboratory you can find the following acids: hydrochloric acid, nitric acid, sulphuric acid, phosphorous acid, carbonic acid.

Some acids, such as citric, boric and tartaric, are solids, butyric acid is a liquid. Many acids arc water solutions of gases. In most cases, however, the significant acid properties do not become evident until the substance has been dissolved.

Chemically, the action of acids is due to the presence of hydrogen ions, H+, that determines its chemical properties. An acid is a substance whose water solution yields hydrogen ions. Acids turn litmus from blue to red and conduct electricity,

What are bases? Bases are substances whose properties are chemically opposed to those of acids. While acids are sour, bases are usually bitter, if you rub some sodium hydroxide solution between your fingers, you will note that it feels slippery. All solutions of strong bases feel the same way because they react with the oil of your skin to actually make soap.

All bases contain the hydroxyl radical, OH-, determining chemical properties of bases. Thus, a base is any substance whose water solution yields hydroxyl ions.

As chemically opposed to acids, bases have opposite properties. To summarize, bases often taste bitter, feel slippery, turn red litmus blue, turn colorless phenolphtalein red, contain one or more of the hydroxyl groups, neutralize acids and finally conduct an electric current in water solutions. Among the most important are sodium hydroxide, potassium hydroxide and so on.

Neutralization is the action between an acid and a base to form a salt and water. The hydrogen ion (H+) of acids combines with the hydroxyl ion (OH) of the base to form water. These ions are charged particles that make all special properties of acid and base vanish.

The metal of the base is now free to join with the nonmetal, or radical of the acid to form salt. Thus, a salt is the product other then water, obtained by neutralizing an acid with a base.

IV. Language development.

Find the odd word in each row.

1. Liquid, solid, water, gas.

2. Sweet, sharp, sour, bitter.

3. Act, neutralize, yield, dilute.

4. Acid, ion, base, alkali.

Complete the sentences.

1. There are 3 classes of chemical compounds:...

2. The Latin word acidus means....

3. There are such acids:....

4. You can meet such acids in the laboratory:....

5. Bases are substances....

6. Bases react with acids....

7. Neutralization is....

Answer the questions.

1. How many classes of chemical compounds do you know?

2. What are acids? Name all the acids you know.

3. What properties do acids possess?

4. What are bases?

5. What are the properties of bases?

6. What is the difference between acids and bases?

7. What is neutralization?

8. What is salt? What way are salts obtained in?

V.Speaking.

1. Make up dialogues answering the questions.

- What are you doing in the laboratory now? What are you studying/investigating?

- Why are you studying it?

- What is new for you in your investigation?

- What are the results you are waiting for?

- How can the results of your investigation be used in industry/ pharmacology (e.g. what is the use of your analyses?)?

- Do you want to continue studying chemistry/pharmacology?

- How can the information you study at the University be useful for you?

- When you graduate from the University, what will your job be? Imagine your ordinary day at work and tell about it.

- Can you synthesize a drug? Which one? If no, what prevents you from doing it?

- What do you think of people preparing drugs at home by themselves?

- How long should you study to be able to prepare drugs? What sciences should you know and what skills must you possess to be able to work as a pharmacist? Explain your idea.





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