62 SCIENCE PRIMERS. [MATERIAL 



when water is raised to the boiling-point. So long as 

 any of the water remains unconverted into steam it 

 becomes no hotter. Moreover the steam itself is at 

 first at 212. 



44. Ice the solid, Water the liquid, and 

 Steam the gas, are three states of one na- 

 tural object ; the Condition of each State 

 being a certain Amount of Heat. 



Ice, liquid water, and steam, are three things as 

 unlike as any three things can well be. What do we 

 mean then by saying that they are states of one sub- 

 stance, water ? 



What we really mean is that if we take a given 

 quantity .of water, say a cubic inch, and change it 

 first into ice and then into steam, there is something 

 which remains identically the same through all these 

 changes. This something is, in the first place, the 

 weight of the material substance. The water weighs 

 252-3- grains, the ice into which it is converted weighs 

 2 5 2\ grains, and the steam produced from it weighs 

 252^- grains. In the second place, the same force 

 would cause the ice, the water, and the steam, to 

 move with the same rapidity ; and, when set in motion, 

 they would produce the same effect upon anything 

 movable against which they struck. 



In the third place, when you study chemistry, 

 you will learn that the ice. the steam, and the liquid 

 water, would yield the same weight of the same two 

 gases, oxygen and hydrogen, and nothing else. 

 Every one cubic inch of water, 1,700 cubic inches of 

 steam, and ijy cubic inch of ice, yield 28^ grains of 



