58 



WATER SUPPLY 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 



Experiment 38. How can hardness of water be re- 

 moved? 



Obtain some water from a faucet in your home or school 

 house or from a well in your neighborhood. Shake soap 

 in the water. Do suds appear soon? If so, it is soft water. 

 Soft water has very little mineral matter dissolved in it. 



If suds do not appear soon the water is hard. If the 

 water is hard, boil some of it. Shake soap in it again. Do 

 suds appear soon? If so, the water possesses only temporary 

 Iiardness, which is removed by boiling. 



If suds do not now appear at once, the water possesses 

 permanent hardness. Add some borax or washing soda to 

 the water. Add soap and shake. Do suds appear at once? 

 Permanent hardness must be removed by the addition of 

 chemicals to the water. 



In your notebook 1 record the notes of this experiment and 

 answer the following questions. 



What do the terms hard and soft water mean? How is 

 temporary hardness of water removed? How is permanent 

 hardness of water removed? Where do the substances that 

 make water hard come from? 



Experiment 39. How is water purified by filtration? 



Tie a piece of cloth over the top 

 of a lamp chimney and place it 

 over a glass vessel (see Figure 

 88). Pour coarse sand into the 

 chimney until it is about half full. 

 Next pour fine sand into the chim- 

 ney until it is about an inch and a 

 half from the top. Prepare some 

 muddy water and pour it into the 

 top of the chimney. 



Record the notes and results of 

 this experiment in your note- 

 book. 2 



FIG. 88. HOW A FILTER 

 WORKS 



Experiment 40. How do cer- 

 tain chemicals help to puri- 

 fy the water? 



Fill a tall bottle with muddy 

 water. Put a small amount of 



alum in it. Allow it to stand for a day and note the change 

 that has taken place. Do you know of any other chemicals 

 besides alum that are used to purify water? 

 Record the notes and results in your notebook. 3 



Experiment 41. How is water purified by distillation? 



Set up apparatus similar to that shown in Figure 89. 

 Draw some water from the faucet and add some dirt, sugar, 

 and salt to it. Put it into the flask and boil for awhile. 



Examine the distilled water which collects in the test 

 tube. Does it have any color? Any odor? Any taste? 



In your notebook 4 record the results of this experiment, 

 complete the following statements, and answer the questions. 



1. When water is distilled it is first _ . and then 



2. The impurities in the water remain 



3. What are some of the uses of distilled water? 



1 See workbook, p. 23. 



2 See workbook, p. 23. 



* See workbook, p. 23. 



* See workbook, p. 24. 



Experiment 42. What is the composition of water? 



Set up apparatus similar to that in Figure 90 or use a 

 Hoffman's electrolysis outfit if you have one. Add cautiously 

 a little strong sulphuric 

 acid solution to the water 

 before putting it into the 

 apparatus (about 5 cubic 

 centimeters). Use about 

 four dry cells connected in 

 a series (carbon of one cell 

 connected to the zinc of 

 another). Connect the 

 wire marked a in the dia- 

 gram to the carbon of the 

 first cell and the wire 

 marked b to the zinc of the 

 last cell. Notice the bub- 

 bles of gas appearing on 

 the small pieces of plat- 

 inum. Notice later the 

 amount of gas collected in 

 each tube. 



When the tubes are partly filled with gas, remove them 

 by means of a glass plate and set them upright. Using a 

 ruler, measure the amount of gas in each jar. Hydrogen 

 will explode with a pop when a flame is brought near it, 

 while oxygen will make the flame burn more brightly. Test 

 the gas in each jar. 



FIG. 89. HOW WATER IS DISTILLED 



FIG. 90 



In your notebook 5 record the notes of this experiment and 

 complete the following statements. 



In each case the gases were . in color. One gas col- 

 lected about as fast as the other. This gas by test 



was proved to be From these observations one may 



infer that water is composed of the two substances . 



and in the proportion of parts of to 



part of 



READINGS WHICH WILL HELP ANSWER THE 

 PROBLEM QUESTIONS 



What is water? We see it in our lakes, streams, and 

 oceans ; in fact, about three-fourths of the earth's 

 surface is covered with water. We pump it from wells 

 or see it flow from our hydrants. We know it exists 

 under the surface of the earth, and we see it in the 

 atmosphere in the form of clouds, rain, or snow. 



In spite of our familiarity with water many of us 

 do not know what it really is. Have you tried to sepa- 



* See workbook, p. 24. 



