CHAPTER X 

 MATTER AND ENERGY 



47. Matter. Matter or material is that which we 

 think of as having weight or mass. Such materials as 

 wood, rock, iron, books, water, air, etc. are what we 

 think of as matter. From previous chapters we have 

 learned that substances may undergo a number of changes. 



For instance, the interaction of a base and an acid 

 brought about a change (13) by which both base and acid 

 were destroyed, but the material composing them was 

 not destroyed. The weight of the salt and water formed 

 by the action of hydrochloric acid on caustic soda (13) is 

 the same as the combined weights of the acid and the 

 base used. When coal is burned the combined weight 

 of the carbon dioxide and other gases formed and the 

 ashes left is the same as the combined weight of the coal 

 and oxygen used to burn it. We can take a board and 

 cut it into pieces and make a box of it, and the weight 

 of the box will be the same as that of the board less the 

 weight of the sawdust and the pieces wasted. 



We have seen many kinds of transformations of matter, 

 but in no case was it destroyed. Its use to man may 

 have been destroyed, but not the material; as when a 

 wagon is wrecked, its usefulness is gone, but the material 

 of which the wagon was made still exists. From our ex- 

 periences with matter we could say that matter cannot be 

 destroyed, but its form and appearance can be changed. 



