JANUARY 131 



weather map sent out by the government, and to be 

 had on application to the Local Weather Bureau. 



PHYSICS 

 Evaporation, Boiling, and Condensation. 



Facts : 



Under the influence of heat, Avater evaporates, that is 

 to say, it passes into the air in the form of invisible 

 vapor. The greater the heat, the greater the surface 

 exposure ; and the stronger the wind, the more rapid 

 will be the evaporation. 



In boiling, the first bubbles that are formed contain 

 air. They break quietly. Soon, however, numerous 

 small bubbles are formed at the bottom and middle of 

 the dish which break explosively, increasing in size as 

 they reach the surface of the water. 



Immediately above the water, or close to the spout 

 of a teakettle, no steam can be seen; but just as soon 

 as this true steam comes in contact with the colder air 

 outside, it is condensed into water dust and becomes 

 visible. The temperature of the water and of the steam 

 does not vary after boiling is Avell under wa}', although 

 of course the fire underneath becomes hotter and 

 hotter. This extra heat causes the water to break up 

 more rapidly. 



Whenever water vapor comes in contact with a colder 

 solid, the water condenses on that solid. 



Method : 



Why do we add water to the aquarium ? Where does 

 the water go? Can we see it? From which would it 

 disappear more quickly, a deep dish or a shallow one? 

 How shall we find out ? 



