Lesson 2

Ex. 1*. Remember the pronounciation of the following words:

Admixture Transport

agent

Granite Homogeneous

Sample Heterogeneous

Ex. 2. Say what part of speech the following words belong to?

Mixture, specific, homogeneous, substance, soluble, gravity, remarkable, enumerated, characteristics, relative.

Ex. 3*. Check up if you remember the verbs: change, state, heat, boil, add, enu­merate, vary, contain, consist of..., possess, prove, account for, discover.

Ex. 4*. Try to remember the following words and expressions: thus, for example, that is, because (of), therefore, in some cases, for instance, those of, both ... and, in order to, at once, in spite of..

Ex. 5. Translate the following sentences. Remember the meaning of the following word combinations: One can - можно One may - можно One must - нужно One should – нужно

1. One can prove that air is not a chemical compound but a mixtire of nitrogen and oxygen with small amounts of other gases.

2. One must remember that this reaction is followed by an explosion,

3. One should take into account that sulphuric acid has a great affinity with water.

4. Looking at the arrangement of atoms in a solid, one can better understand its properties.

5. One may see that this substanceis from mixture.

6. One must have substance in its pure form.

7. One can call it a mixture, because it contains different amounts of substances,

Ex. 6. Read and translate the text,

CHEMICAL SUBSTANCES

Substances are distinguished by their properties. For example, one can state that sugar is a hard, brittle substance, white in color, sweet to the taste, without odour, easily soluble in water, heavier than water and it tumes brown when it is heated, etc. In order to learn the properties of a substance one must have it in its pure form.

Even small admixtures of foreign substances may change the properties of a substance. For instance, pure water is both colorless and transparent, but if a drop of milk is added to a glass of water, the water becomes clouded; if a drop of ink is added, the water becomes colored. All the enumerated properties are not those of water, but they are properties of the admixtures.

In some cases, one may see at once that a substance is heterogeneous, that is, a mixture of different substances. Granite, cement, coal are examples of non-homogeneous materials; they consist of mixtures of substances. Thus, granite is a mixture of varying quantities of silica, feldspar and mica; each of them possesses its own properties. Coal is not a substance too because different samples contain different relative amounts of ash, water, carbon and other components.

Every material, therefore, consists of a single (pure) substance, or it is a mixture of two or more substances, each of which retains in the mixture its own characteristic properties.

Ex. 7. Group up antonyms, translate them: similar, soluble, heterogeneous, transparent, colourless, pure, heavy, easily, hard, homogeneous, insoluble.

Ex. 8. Choose the correct English equivalent to the Russian terms:

1. примесь a) carbon

2. углерод b)mixture

3. образец с) property

4. неоднородный d)transparent

5. свойство е) admixture

6. летучесть f) heterogeneous

7. удельный вес g) sample

8. прозрачный h) pure

9. чистый i) volatility

10. смесь j) specific gravity

Ex. 9. Group up the words in three columns. Translate them.

Properties Substances Mixtures

Silica, smell, mica, milk, hardness, coal, carbon, ash, melting point, colour, feldspar, volatility, specific gravity, granite, boiling point, water, taste, sugar cement.

Ex. 10. Answer the questions:

1. What are the properties substences distinguished by?

2. Is sugar easily soluble in water?

3. What colour is sugar?

4. Is sugar lighter or heavier than water?

5. What taste has sugar?

6. In what form must one have a substance in order to learn its properties?

7. What may change the properties of a substance?

8. What happens if a drop of ink is added to a glass of water?

9. What substances does granite consist of?

Ex. 11*. Translate the sentences from Russian into English.

1. Все окружающие нас предметы состоят из веществ.

2. Они состоят из одинаковых молекул.

3. Гранит состоит из нескольких веществ.

4. Следовательно, гранит состоит из разных молекул.

5. Химия изучает вещества и их состав.

6. Она также изучает процессы и законы, по которым изменяется их состав.

Ex. 12. Characterize the following substances: milk, sugar,water, salt.

Ex. 13. Choose your own substances and characterize them.