CONDUCTION OF HEAT 27 



immersed, and note the temperature of the water as it begins to 

 freeze. Compare it with the temperature at which ice melts. 



EXERCISE 23 

 BOILING POINTS OF WATER AND ALCOHOL 



Apparatus and Materials. A thermometer reading above 100C., 

 a flask or cup, a beaker, a test tube, a ring stand or other support, 

 water, salt, and alcohol. 



a. Examine your thermometer, and be sure it reads above 

 100 C. Place a flask that is half full of water over a flame, and 

 heat the water to boiling (see Fig. 54, 62, of the text). Sus- 

 pend, or hold, a thermometer in the flask. At first have the 

 bulb in the boiling water; then hold it in the steam above the 

 water. What is the boiling point of water, according to your 

 thermometer? 



6. After you have found the boiling point of ordinary water, 

 put into the water about % its volume of salt, and heat the 

 water to boiling until as much as possible of the salt dissolves. 

 What is the highest temperature reached now? 



c. In a beaker, or cup, of boiling water put a test tube con- 

 taining about 5 cu. cm. of alcohol, and hold a thermometer in 

 the test tube so that the bulb is just below the surface of the 

 alcohol. At what temperature does the alcohol boil? 



EXERCISE 24 

 CONDUCTION OF HEAT 



Apparatus and Materials. Iron and copper wires about 15 cm. 

 long, glass tube or rod of same length, burner, test tube of water, test 

 tube holder. 



a. Conduction by Iron, Copper, and Glass. In a flame hold 

 a piece of iron wire and one of copper, each about 15 cm. long. 



