IV. WATER, AND ITS USES 

 SOME PROPERTIES OF WATER 



Water is indispensable in the life of all plants and animals. 

 In the human body it makes possible the solution (digestion) 

 of foods. It is the means employed in the body for removal 

 of waste through the skin, bowels, and kidneys. It keeps 

 moist the tissues so that they can perform their several 

 functions. In Physics a study is made of water as a type 

 of all liquids. In Chemistry both its physical and chemical 

 properties are studied, together with its usefulness in pro- 

 moting chemical change and in carrying on the chemical 

 processes. In the study of Physical Geography, and in 

 Meteorology, water as an agent in the changes that occur is 

 of first importance. In matters of hygiene and sanitation, 

 and in the affairs of the household, the importance of water 

 in daily life can scarcely be emphasized sufficiently. In the 

 affairs of men and of nations water is a highway for foreign 

 and domestic commerce, while water and steam furnish a 

 large part of the power that turns the wheels of the world 's 

 industries. Any extended consideration of its usefulness 

 to individuals and to mankind generally by reason of its 

 properties and its abundance leads into every field of human 

 activity. . 



All matter, including liquids and gases, is supposed to be 

 made up of minute particles called molecules. These are 

 too small to be seen through the most powerful microscopes. 

 It is further supposed that these molecules as units of matter 

 are separated by spaces relatively large as compared with 

 the size of the molecules themselves. And it is believed that 

 these molecules are incessantly moving back and forth in 



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