76 LABORATORY EXERCISES 



If there is no sample faucet at school, get some one at home, 

 or a plumber, to take a faucet apart for you and to show you 

 how it works. Which of the two in the figure does it resemble? 

 When a faucet leaks, so that you cannot cut off the water, what 

 part is usually out of order? Which is the more likely to get 

 out of order, the cold-water faucet or the hot-water one? 

 Why? 



6. Examine a "trap." Make a drawing showing how the 

 trap would look if cut lengthwise. Is the trap like that shown 

 in Fig. 200, 236, of the text? If not, how does it differ? 



If a trap is stopped up, how should you clean it? How does 

 a trap form a "water seal"? Why is a water seal necessary? 

 Suppose that strings and hair collect in a trap, so that they 

 extend over the bend shown on the right of Fig. 200 (the text) , 

 would they be likely, or not, to carry away the water of the 

 trap? See Fig. 25, 32, text. Why should such materials not 

 be allowed to accumulate in a trap? 



c. Examine an old piece of lead pipe, such as an old trap. 

 Is there any evidence of its having been worn thin? What 

 wore it thin? If grease is deposited in a trap attached to a 

 kitchen sink, what could be used to "cut" the grease? Why 

 should the cutting substance not be left standing in a lead 

 trap for a long time? 



EXERCISE 73 



FLAMES 



Apparatus and Materials. Iron spoon, burner, candle, glass tube 

 about 10 cm. long, kerosene lamp, matches; materials for an alcohol 

 lamp, if needed (see e). 



a. Hold an iron spoon in the luminous flame of a burner or 

 candle. What happens? Where does the soot come from? 

 What is soot? 



