Make up situations using the English equivalents of the words given above. 40. Find in the text the synonyms to the following words:

40. Find in the text the synonyms to the following words:

41. Find in the text the antonyms to the following words:

42. Give Russian equivalents to the following word combinations:

To purify water; pure fresh water; potable water; potential energy; contaminated mixture; unfrozen water; low temperature;freezing temperature; salt water; ice cube; desalination plant; to be less economical

43. Find the correct words in Text 12D to complete the sentences:

1 .The ice that forms when sea water ___ is essentially pure fresh water.

2. Purification effect results from a ___ between energy and disorder.

3. As long as the water freezes slowly, the ice crystal it forms will have very little ___ in it.

4. When you freeze a bucket of salt water, the ice that forms first contains very ___ salt.

5. When you freeze ice cubes, the outer surface freezes first and the ___ become concentrated near the middle of the cube.

44. Work with a partner. Take turns to ask and answer questions to text 12D. Use the words and word combinations below:

45. Fill in the gaps with the prepositions from the box:

Water Treatment

___ ancient times ___ the present, water filters have evolved out of necessity, first to remove materials that affect appearance, then to improve bad tastes and finally to remove contaminants that can cause disease and illness. Wells, canals, aqueducts, reservoirs and distribution pipes were built as a community effort to bring water ___ a central supply. These waterworks were built ___ the Egyptians, Babylonians, Mesopotamians, Persians and Phoenicians centuries before the birth of Christ.

The earliest record ___ the beginnings ___ water treatment is linked to Hippocrates (known as the «Father of Medicine») ___ the 4th century B.C. He advised boiling water to improve taste and then filtering through a cloth bag. Pliny the Elder (23-79 A.D.), ___ his Historia Naturalis, discusses the characteristics ___ potable water. ___ Egypt and China they put alum ___ tubs to clarify the water. ___ 1935, Sir Henry Doulton, ___ the Royal Doulton china company ___ London ___ the UK, invented the ceramic cartridge ___ removing bacteria from water.

In more recent times, treatment ___ water to remove pathogenic organisms began around 1892 after Dr. Robert Koch traced the cholera epidemic in Hamburg, Germany, to its unfiltered water supply. Since 1855, ___ London, England, a parliamentary statute required its water supply to be filtered through slow sand filters. Slow sand filters were introduced ___ the United States around 1870 and a modern rapid-sand filtration plant was built ___ 1902 at Little Falls, NJ. In 1909, liquid chlorine was developed ___ disinfection ___ water supplies.

Consult the TEXTS FOR SUPPLEMENTARY READING and learn about the use of chlorine to purify water (Text 49), about water filtration at present (Text 50) and the future of water filtration (Text 51). Be ready to discuss the information you have read.