CHEMICAL CHANGE AND THE METHODS OF STUDYING IT 23 



the natural order of the universe. It is thought that we are try- 

 ing to find the boundaries of chemistry, as they have been pre- 

 determined by nature, and to discover the facts, relations of 

 facts, and laws which nature has provided as a means of classify- 

 ing the content of the science. Now, the situation is precisely 

 the reverse of this. Nature provides only the materials and the 

 phenomena, and man is attempting to classify them. He divides 

 the whole into groups, such as physics, chemistry, botany, etc. 

 Then he classifies the facts within each group, in order that he 

 may more easily remember them and perceive their relations. 

 He often finds that, when new facts are discovered, parts of the 

 classification have to be changed. 



In the preceding pages, we have discussed some of the ways 

 that have been invented for classifying the materials and facts 

 assigned to chemistry. Thus, we pick out a number of facts of a 

 like nature and try to make a single statement which will cover all 

 these facts. For example, we find about one hundred thousand 

 different substances and, in the case of each substance, every speci- 

 men that we have examined contains the same proportions of 

 the constituent elements. So we formulate the law of constant 

 proportions. 



A law or generalization in chemistry is a brief statement 

 describing some general fact or constant mode of behavior. We 

 must remember, however, that laws are only true so long as no 

 facts in conflict with them are known. There are no laws in 

 nature. Nature presents materials and phenomena as she pleases. 

 The laws are parts of science, which is made by man, and is a de- 

 scription of natural facts as man knows them. 



One section (p. 9) was entitled: " Explanation of rusting." 

 If that paragraph be now re-read, it will be found that, in the 

 ordinary (as distinct from the scientific) sense of the word, no 

 explanation was given! When we ask a man to " explain " some 

 feature in his conduct, we recognize that he might have chosen to 

 act otherwise, and we wish to know why he acted precisely as he 



