Read about ordinary water and transform the word given in bold at the end of each line into a suitable form that fits the space in the same line

Read about ordinary water you know much about and fill in the gaps with the words given in the box.

Notes on the Text

1. in contrast to – в противоположность

2. any given sample – любой имеющийся образец

3. one and a half times – в полтора раза

4. index of refraction – коэффициент преломления

5. 10 times larger – в 10 раз больше

14. Answer the following questions:

1. How do physical chemists regard the properties of liquids? 2. What is the difference between liquids and gases/ crystalline solids? 3. What is the choice of a cubic centimeter of water as the international unit of mass motivated by? 4. What the index of refrac­tion of water has less value? 5. When are the molecules of Water II broken down into ordinary molecules of H₂O? 6. What hypothesis has the Russian scientist Vasiliev expressed?

15. Find the pairs of synonyms and remember them:

at once, learn, stable, mainly, several, ratio, chiefly, find out, almost, immediately, get, nearly, proportion, obtain, invariable, some.

16. Find the pairs of antonyms and remember them:

impossible, stable, purity, solidify, unstable, indefinite, liquefy, impurity, definite, possible.

consist, compound, constants, composition, constituent, contains, condensation, greasy, fraction, distillation, crystallization, vapour, dissolves, solvent, investigate, impure, matter, nearly

Water is hydrogen oxide, a (1) … of hydrogen and oxy­gen. It is a major (2) …of living matter and of the environment in which we live.

Most of the world's water is liquid, but an important (3) … is solid as ice and snow.

Many mineral substances contain water of (4) … (e.g. copper sulphate) and in the atmosphere there are millions of tons of water vapour. Clouds (5) … of minute droplets of water or crystals of ice.

Water (6) … a very large number of substances and is the most important (7) …. It does not dissolve fatty or (8) … substances and most plastics.

Having found the (9) … of water, the scientists could (10) … its properties. It was stated that ordinary water is (11) …, it usually contains dissolved salts and gases and sometimes organic (12) ….

For chemical work water is to be purified by (13) …. Rain water formed by the (14) … of water in the air is (15) … pure water. Nowadays it (16) … considerable proportions of the industrial dust and gases.

Physical properties of water can be used to define many physical (17) … and units.

Salts are _1_ in most solvents but they are soluble in water. Gasoline, benzene are good _2_ for grease, rubber, organic materials _3_, but they do not dissolve salts. The reason that water is so _4_ for salts is that it has a very _5_ dielectric constant and its molecules tend to combine with ions _6_ hydrated ions. Both of these properties are due to the large _7_ dipole moment of the water molecule. Having _8_ these properties, we can understand that water _9_ moleculehas a considerable amount of _10_ character.

soluble solution general effect highly form electricity study molecular ion

19. Translate the following sentences paying attention to the words in bold type:

1. Rain water is nearly pure water. 2. Sea water contains nearly 3.6 per cent of mineral matter in solution. 3. Pure substances may be of one or two kinds viz. elements and compounds. 4. If we weigh the hydrogen and oxygen liberated in the electrolysis of water, we find that the oxygen weighs 8 times as much as the hydrogen. 5. The volume of ice is greater than that of the same weight of water. 6. That the solid dissolves in water can be found by a number of ways. 7. You can use any sample in your work. 8. The number of substances that water dissolves is practically unlimited.

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