UNIT III. THE RELATION OF THE WATER SUPPLY 

 TO THE WELFARE OF THE COMMUNITY 



There are three necessities without which man can- 

 not exist : air, food, and water. The last of these, 

 water, because it is such a common thing, is often not 

 appreciated. We are so accustomed to going to a well 

 or a faucet for water whenever we are thirsty or wish 

 to take a bath that we seldom stop to consider how 

 not only our comfort but our very life is directly de- 

 pendent upon it. Without water all plants and animals 

 would die and our earth would soon be a barren 

 place. 



Water is important to us personally. Since the hu- 

 man body is more than 65 per cent water, we must 

 drink large quantities in order to live. Water carries 

 dissolved foods in the body and is necessary for the 

 removal of waste matter. Large quantities of water 

 are also used in our homes and communities to keep 

 them clean. These services are of inestimable value 

 in adding to our health and happiness. 



Think of the tremendous importance of water to 

 our industries. Large quantities of it are needed in 

 boilers to form steam. It is the best and cheapest 

 solvent 1 for many purposes. It is also a source of 

 much power. More and more streams and falls in this 

 country are being harnessed to furnish the energy 

 to generate electricity. 



There are many other ways in which we use water. 

 Perhaps you will find it interesting to make a list of 

 all the ways you can find in which man makes use of 



1 Solvent, a substance which dissolves other substances. 



water. In this unit you will learn many new and inter- 

 esting things about water. You will learn what it is, 

 how it is purified, what the dangerous impurities in 

 it are, and how it is controlled and distributed to our 

 homes. 



What do you already know about water? Write the 

 answers in your notebook under the proper head- 

 ing. 



1. How long can you live without water? 



2. Why must living things have water? 



3. What is the source of the drinking water in your 

 home? How is it kept clean and pure? 



4. Is ice a form of water? Is snow water? What is 

 water? 



5. How can water in the home be made safe for 

 drinking purposes? 



6. How do large cities keep their water supply clean 

 and pure? 



7. What is hard water? Soft water? 



8. Are the streams in your community being pol- 

 luted 2 ? If so, what are the principal sources of the 

 pollution? 



9. What are the dangers to a community of im- 

 proper methods of sewage disposal? 



10. Where does the water in wells come from? 



11. Have you any leaky faucets in your home? How 

 do you repair a faucet? 



'Polluted, made impure. 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What is water? 



2. What impurities are commonly found in 

 water? 



3. How are chemical impurities removed from 

 water? 



4. How is water purified in the home? 



5. How is water purified by distillation? 



6. How are temporary and permanent hardness 

 removed from water? 



TOPIC 1. METHODS OF PURIFYING WATER 



2. You may be able to carry out, on a small scale, 

 some of the methods used to purify water. Read the 

 experiments suggested in the next section. 



3. Study the following words and see if they are 

 new or difficult for you. 



SUGGESTIONS AND HELPS FOR STUDY 



1. The safeguarding of the water supply is an im- 

 portant problem for every home and every commun- 

 ity and often a difficult one. Study the problems care- 

 fully in order to learn what impurities may be found 

 in water. The study of this topic will teach you how 

 they may be removed. 



sterilize to free from disease germs. 



disinfectant a substance which purifies by killing dis- 

 ease germs. 



bacteria tiny one-celled plants. 



soluble capable of being dissolved. 



solution a substance in which some other substance is 

 dissolved or the mixture resulting when a substance 

 is dissolved in another. 



hard water water which contains dissolved sub- 

 stances. 



insoluble not capable of being dissolved. 



solvent a liquid in which other substances can be dis- 

 solved. 



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