A Choose the best variant to complete the sentences

1. Damage to the layer of ozone in the high atmosphere by human activity is (difficult, complex, troublesome, hard) esoteric, and completely invisible to anyone but the scientists who are studying the issue.

2. By absorbing ultraviolet sunlight, ozone deposits the heat associated with this light into that level of the atmosphere, thus (making, organizing, creating, arranging) a layer much inner than those immediately below.

3. Thus, strong barriers prevent chlorine from (getting, reaching, touching, matching) high in the atmosphere, unless people contrive to put it there.

4. As scientists' understanding of the chemical reactions that create and destroy ozone increased, it became (clear, pure, obvious, evident) that relatively small quantities of some substances could change these reactions and hence the amount of ozone in the stratosphere.

5. People who twenty years ago had never heard the word ozone are now (excited, worried, concerned, provoked) about its disappearance

B Mark statements true or false, correct the false ones.

1. It is in this inner layer that disturbing changes are occurring.

2. Suppose we did wish, for some reason, for chlorine at the Earth's surface to move out of the atmosphere, we would have to arrange for the emission at the surface of the Earth of a chlorine-containing gas.

3. Chlorine, an effective chemical catalyst that can change ozone into normal oxygen, is appearing in rapidly increasing concentrations in the atmosphere.

4. Chlorofluorocarbons, indicating that they contain carbon, fluorine, chlorine, and sometimes hydrogen, are frequently abbreviated to CO₂, and a numbering scheme is used to tell how much of each element is in the molecule of the particular CO₂ under discussion.

5.It is known that ozone plays an important role in the high atmosphere in addition to screening out UV-B.

 

C Translate from English into Russian in written form.

 

1. Oxygen usually consists of two molecules, but in the form O₃, it has 3 molecules. O₃ is a pale blue gas which when concentrated can easily explode, and it causes the dark colour in the sky when there is a storm.

2. It is created by nitrogen oxides and hydrocarbons from car exhausts and it is the most dangerous chemical in air pollution in our cities.

3. But if O₂ is bad for life near the ground, high in the atmosphere is good for life.

4. Here it is destroyed by chlorofluorocarbons produced by fridges, sprays and air conditioners, and in 1985 scientists noticed for the first time that above Antarctica there was now a hole in the O₃ layer.

5. This hole lets in ultraviolet rays from the sun, which in the next seventy years will cause at least seven million extra cases of skin cancer in the United States alone.

 

D. Read the text again and answer the following questions.

1. How does ozone deposit the heat into the atmosphere?

2. What can reactions change chemical reactions and hence the amount of ozone in the stratosphere?

3. What would we have to do if we wished for chlorine to move into the atmosphere?

4. What substances is abbreviated to CFC?

5. What happens to CFC-11 and CFC-12 in the air?

Вариант

1. Read the text and translate the extract in italic in written form.