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I .Arrange, the words to form a sentence.

1 the atmosphere, some water vapor, contains. 2. near industrial plants, fogs, are rare. 3. occur, in cold countries, ice fogs. 4. a cloud, is, fog, on the ground. 5. condense, the droplets, in the air, on tiny particles of dust. 6. become, particularly dense, fogs, near industrial plants.

II. Answer these questions in short simple sentences. Your answers must follow each other so that all your sentences will form a complete paragraph. Your paragraph will be a precis of the piece.

1. What do we call fog?

2. What is the shape of the droplets of fog?

3. What does the transparency of a fog depend upon?

4. Why does not fog disappear through fallout of the water particles?

5. What is the water vapor of atmosphere supplied by?

6. Where do the droplets condense?

7. What happens with the nucleus on which the water condenses?

8. Why do droplets of solution grow in size?

9. What does the density of a fog depend on?

10. Where are fogs particularly dense?

III. Explain the meaning of the italicized words and phrases as they are used in the passage.

IV. Join the following sentences using the connecting words in brackets. Omit the words in italics.

  1. Ice fogs usually occur only in extremely cold climates. The water droplets in a cloud solidify only if the air temperature is far below freezing, (because).

  2. The droplets in fog-creating conditions are buoyed up by rising air currents. The droplets are continually replaced by new droplets condensing from the water vapour in the air (either… or).

  3. The saturation point is lower in solution than it is for pure water. The droplets of solution tend to condense more water vapor on them and grow in size. (because).

  4. Fog is a cloud on the ground composed of tiny droplets of water. Fog is a cloud on the ground composed of ice crystals, (either... or).

  5. The water droplets in a cloud do not solidify. The air temperature is far below freezing. (until).

6. Water is 800 times denser than air. The droplets of water fall at the predictable rate.(since).

7. The nucleus on which the water condenses may be a soil particle. The nucleus may be grain of sea salt. (either... or).

V. Instead of saying: Fog is a cloud on the ground, which is composed of tiny droplets of water. We can say: Fog is a cloud on the ground composed of tiny droplets of water.

Change the following sentences accordingly.

  1. The atmosphere contains some water vapor, which is supplied by evaporation from different bodies of water.

  2. The droplets of water condense on tiny particles of dust in the air which are called condensation nuclei.

  3. Ice fog is a cloud on the ground, which is composed of ice crystals.

Complete the following sentences.

1. A cloud on the ground composed of ... is called fog. 2. Water vapor supplied by … forms a part of the atmosphere. 3. Tiny particles of dust called ... initiate condensation at subsaturation humidities.4. The droplets are fully … and fall at the predictable rate. 5. The atmosphere always contains some water vapor, supplied by … from different bodies of … , vegetation and other sources.6. The droplets condense on tiny … of dust in the air called condensation nuclei.