Ex. 12. Read and translate another text on water.

Water is hydrogen oxide, a compound of hydrogen and oxygen. It can be made if hydrogen or a hydrogen-containing substance is burnt in air or oxygen.

Most of the world's water is liquid, but an important fraction is solid as ice and snow.

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

Water dissolves a very large number of substances and is the most important solvent. It does not dissolve greasy, fatty substances or most plastics.

After they had found the composition of water, the scientists could investigate its properties. It was stated that ordinary water is impure, it usually contains dissolved salts and dissolved gases, and sometimes organic matter.

For chemical work water is to be purified by distillation. Pure water is colourless, tasteless, and odourless. Rain water formed by condensation of water in the air is nearly pure water, which contains only small proportions of dust and of dissolved gases.

After the examination of water properties the chemists found hat physical properties of water can be used to define many physical constants and units.

The freezing point of water (saturated with air at 1-atm pressure); taken at 0° С and the boiling point of water at 1 atm is taken as 1100° С

The unit of volume in the metric system is chosen so that 1 ml of water at 3.98° С (the temperature of its maximum density) weighs 1,000 g/cm.

So water is one of the most important of all chemical substances. It |is a major constituent of living matter and of the environment in which we live.

Ex. 13. Read and translate the following words both as nouns and verbs:

change, state, water, mark, influence, increase, decrease, experiment, experience, comment, matter

Ex. 14. Match antonyms in A and B:

Ex. 15. Change the given sentences into indirect speech.

1. The author writes: "Three-quarters of the Earth is covered with water."

2. The writer asks: "Is it possible to make water from its elements?"

3. The scientists stated: "The radiation from thorium nitrate is unsteady."

4. Rutherford remarked: "It's really very fine to see the things one has seen in imagination visibly demonstrated."

5. He said: "I have already drawn your attention to the social implications of the release of atomic energy."

6. Pauling often repeated: "I keep on the outlook for aspects that I don't understand."

7. The scholars usually asked: "What causes electrons to change or bit?"

8. They also asked: "Is the electron a wave or a particle?"

Ex. 16. Work in pairs. One student reads the given statements, the other pretends that he does not hear and asks him/her to repeat. Take turns. You are given an example:

Example: STUDENT A: When H₂O falls from clouds it’s called a rain.

STUDENT B: Where did you say it falls from?

or

What from did you say it falls in?

STUDENT A: I said it falls from clouds.

or

I didn’t. But it falls in a liquid form.

1. When H₂O falls in small frozen crystals, it’s called snow.

2. When the snow begins to melt, it’s called slush.

3. If the slush freezes again and becomes hard and solid, it’s called ice.

4. The combinations of rain and snow is known as sleet.

5. Small round lumps that fall during a thunderstorm are called hail.

6. The H₂O forming on the leaves and flowers is a dew in warm weather.

7. The same in cold weather is frost.

8. The H₂O united into a liquid body which is relatively motionless may be a puddle, a pond, a lake, a sea, or even an ocean.

9. While the water moves, it may be a brook, a creek or stream, or a river.

10. When H₂O comes out of the tap, it is just plain water.

Date: 2016-01-03; view: 1707