IMGP5597 [1600x1200]

UNIT 10

The Atmosphere

Life on our planet depends on the presence of a thin layer of air. Thiś layer of air is the reservoir from which we draw oxygen necessary for metabolism, carbon dioxide used in photosynthesis and nitrogen essential to plant growth. The tracę constituents of the atmosphere have effects on the balance of life. Ozone at an elevation of about 30 km absorbs harmful ultraviolet radiation of the sun but near the earth surface promotes the photochemical reactions responsible for smog formation.*

The development of rockets and satellites madę it possible to explore the upper atmosphere. Mass spectrometers and spectrophotometers carried by these vehicles are used to detect species such as O_v O and 0,⁺ which are unstable in the laboratory. ^There is still much to be learned about the upper atmosphere, The region between 50 and 85 km is difficult to study because it is too high for balloons and most aircrafts and too Iow for earth satellites. The information we have about this region comes from rockets.

The regions of the atmosphere are defined in terms of their temperaturę. The troposphere extends up to II km and the temperaturę is about -55°C. In the stratosphere the temperaturę rises to about 0°C at 50 km due to the absorption of ultraviolet radiation by ozone. At the upper limit of the mesosphere above the ozone layer it drops to about -90°C. In the lower part of the thermosphere it increases approaching a constant value of about 1200°C at 400 km.

I. Make questions to which the following are the answers:

1.    Wliat..........? Oxygen for metabolism, carbon dioxide in photosynthesis

and nitrogen to plant growth.

2.    What is..........? By ozone.

3.    Where..........? Near the earth surface.

4.    Which part..........? The upper atmosphere.

5.    What..........? Mass spectrometers and spectrophotometers are used.

6.    Why..........? Because they are unstable.

7.    What..........for? For balloons and most aircrafts.

8.    What..........from? It comes from rockets.

9.    What........'.. on? It depends on temperaturę.

10.    How many_____ ^.'.- ? We can distinguish four regions: troposphere, stratosphere,

mesosphere and thermosphere.

II. Give verbs from which the following nouns are formed:

conclusion, precipitation, indicator, concentration, combination, ionization, reaction, mixture, neutralization, preparation, purification, oxidation, action, addition, treatment, absorption, difliision, division, replacement, evaporation.