9 8 



GENERAL SCIENCE 



NH. 



difference between the solid, liquid, and gaseous forms of 

 a body is in their rate of molecular movements, and in the 

 size of the spaces (" pores") between the molecules. An 

 hypothesis in science is a supposition used as an explanation 

 of phenomena. Systematic advance in scientific knowledge 

 makes large use of hypotheses. It must always be remem- 

 bered, however, that these hypotheses are based upon what 

 is known to be true, and that they are always subject to change 

 to accord with any newly discovered facts. 

 A belief found to have wide application, and always found 



true to the facts of the 

 natural world wherever it 

 is applicable, is known as 

 a "law" in science. It 



j j I (<jas) may be noted here that 



\J as ) / \^ X V. civil and military laws on 



the other hand are re- 

 quirements that certain 



Fir, 34.-Diffusion of gases. named thin g S sha11 be 



done or shall not be done. 



The penalty for disregard of any of nature's laws is not 

 imposed by any court or judge. It follows as a natural 

 consequence of failure to observe them. This is just as true 

 when ignorance occasions the offense as when done wilfully 

 and by design. 



When like states of matter intermingle by reason of their 

 own molecular activities, the change (phenomenon) is called 

 diffusion. Owing to the relatively strong attraction be- 

 tween the molecules of solids scarcely any diffusion takes 

 place between them at ordinary temperatures even when 

 in close contact. When molecules of unlike states of matter 

 intermingle the phenomenon is called absorption. If as 

 result of either absorption or diffusion a homogeneous (ho- 

 mo-ge'ne-iis) liquid results, the term solution is preferred 



