Кислоты и основы

ACIDS AND BASES

I. Starter

1. Discuss the following questions:

1. What is the difference between acids and bases?

2. What is characteristic of many fruits?

II. Active Vocabulary

2. Memorize the following words and word combinations that will help you to cope with the content of the text.

Familiar                                знакомый

to constitute                        составлять

property                                свойство

compound                             соединение

dilute                                      разведенный, разбавленный

vinegar                                    уксус

to correlate                           соотнисить

to adopt the scale                принимать шкалу

extent                                     величина

to measure acidity               измерять кислотность

in terms of                             в следствии

to dissolve                             расстворять

soap                                       мыло

replaceable                           замененный

to attach                               присоединять

III. Work with Text

3. Read and translate the text

ACIDS AND BASES

Every student of chemistry is familiar with the definitions of acids and bases. Acids and bases constitute a group of electrolytes of great importance to biology and pharmacy as well.

Acids and bases are extremely useful substances and we have much information about their properties. Acids are compounds which contain hydrogen; most acids contain oxygen. In water solution they yield H+ ions which are loosely attached to water molecules as oxonium ions. All acids contain replaceable hydrogen, have sour taste, neutralize bases, conduct electricity and turn blue litmus red.

An acid can be produced by heating salt of the acid with sulphuric acid or by the reaction of water with acid anhydrides. Acid anhydrides are non-metallic oxides in terms of their ability to combine water and to form acids.

One of most important acids is hydrochloric acid. We know it to be formed by dissolving hydrogen chloride in water. Some other important acids are sulphuric, nitric and acetic acids.

All of you have noticed the sour taste of many fruits. This is the typical taste of a dilute acid. Lemons contain citric acid, grapes contain tartatic acid, rhubarb and spinach contain oxalic acid, green apples contain malic acid. In addition vinegar contains acetic acid and sour milk has lactic acid present in it.

Bases are hydroxides of metals. They are the chemical opposites of acids. Most bases are electrovalent compounds. When dissociated with water they turn into ions. Among the more important bases are sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonium hydroxide.

The properties common to all water solution of bases are a bitter taste, feel soapy, neutralize acids, conduct electricity and turn red litmus blue.

Bases may be made by adding active metal to water, by combining metal oxide with water, or by combining salt with soluble base.

Acidity and basicity are relative properties of molecules. A particular compound can be an acid relative to one material and a base relative to another. Water provides an example of those relations. Acidity of an aqueous solution is normally measured in pH. The pH scale applies only to aqueous media. Since most reactions and associated acidity relations are carried out in non-aqueous solutions, the pK scale has been adopted.

4. Answer the following questions.

1. Who is familiar with the definitions of aids and bases?

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2. Are acids and bases of great importance to biology and pharmacy?

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3. What do acids contain?

_____________________________________________________________________________4. Where do acids yield H+ ions?

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5. What can an acid be produced by?

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6. Which is one of the most important acids?

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7. What are bases?

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8. Where do bases turn into ions?

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9. What kind of acid do lemons contain?

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10. Why has the pK scale been adopted?

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IV. Language Work

5. Give the appropriate Russian equivalents to the following words and word combinations:

1. sour taste

2. as well

3. sulfuric acid

4. in terms of

5. vinegar

6. litmus

7. dissolve

8. loosely attached

9. dilute acid

10. measure acidity

6. Fill in the blanks with "to teach, learn, study".

1. Yesterday I_____________________ that a foreign professor would deliver a lecture at оur

University.

2. We_________________ the properties of acids and bases in the first term.

3. John __________________three foreign languages. He can read and write these languages very well.

4. My friend made up his mind to_____________________ play chess. He is rather capable.

5. Every lesson wе_________________many interesting things at the University.

6. To know English better one must _________________________ many words as possible.

7. Rearrange the following jumbled words to form sentences.

1. Water, with, turn, most, ions, bases, dissociated, into.

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2. Of, chemical, bases, opposites, are, the, acids.

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3. And, acids, information, the, of, bases, about, much, properties, scientists, have.

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4. To, media, applies, Ph, only, the scale.

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5. And, acids, information, the, of, bases, about, much, properties, scientists, have.

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8. Compose sentences ofyour own using the vocabulary ofthe unit.

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