WATER, AND ITS USES 



43 



are far away from large bodies of water, how do you 

 account for a supply of atmospheric moisture sufficient for 

 an ample rainfall ? 



4. Describe the difference 

 in conditions that result in 

 the formation of (a) dew 

 and rain ; (6) white frost and 

 snow; (c) fog and cloud. 



Why is it that steam is 

 visible near the mouth of 

 a teakettle of boiling water *\ G - 18 'T Grea ,S cloud masses result 



from the condensation to minute 

 water particles of the water vapor 

 in ascending air currents. 



and disappears a little far- 

 ther outward? Why is 

 there no appearance of this "steam" close to the outlet? 

 5. When should a gaseous form of matter be spoken of 

 as a vapor rather than as a gas? 



HEAT OF VAPORIZATION, AND OF FUSION 



1. Take frequent temperature readings as the teacher 

 heats some ice cold water containing small lumps of ice. 

 The water must be stirred continuously with a thermometer, 

 and heated slowly till the ice is melted and the water boils. 

 Record the temperature (a) at the beginning ; (b) from time 

 to time while the ice is melting; (c) during the time until 

 the water boils ; (d) while the boiling water is heated more 

 and more. 



2. Observe the temperature of the room as registered 

 by a thermometer. Wet the bulb of the thermometer with 

 alcohol (or water), and wave it back and forth in the air. 

 Observe the lowest temperature it records. 



