CHAPTER II 



CHANGES AND COMPOSITION OF LIFELESS AND LIVING 



MATTER* 



IN our later studies of living things (animals, plants, and 

 man) we shall often need to have in mind some important 

 facts and principles relating to the composition of both 

 living and lifeless things and to the changes which occur 

 in them ; and these are outlined in this chapter. 



6. Three States of Matter. Soil, water, and air are 

 forms of lifeless matter which are examples of the three 

 states, solid, liquid, and gaseous, in which matter exists. 



Matter in one of these states may be transformed into 

 either of the other states. Thus water, which is ordinarily 

 liquid, may be cooled and frozen into ice (the solid state), 

 or it may be heated and changed into vapor or steam (the 

 gaseous state). Iron and other common metals, which are 

 ordinarily solid, may be melted into the liquid state and at an 

 extremely high temperature may even change to a gaseous 

 state. Liquid air is made by reducing the temperature to 

 312 F. by subjecting air to great pressure in powerful 

 machines. 



7. Physical Change. In all such changes of matter from 

 one state to another (from solid to liquid, or to the gaseous, 

 etc.) the same substance continues to exist. Ice is only 

 solid water, steam is a gaseous state of water, molten iron 

 cools into solid iron, and sugar and salt will dissolve in water. 

 In .these cases there has been a change in the state of matter, 



* Students who have previously taken courses in chemistry and physics 

 should read this chapter as a review of familiar facts, but from a new view- 

 point. 



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