CHAPTER II 



Properties of Elements and Compounds 

 13, Physical Properties. In order to determine the 

 value of any element or compound, a knowledge of its 

 chemical and physical properties is necessary, and it is 

 important that a clear idea be obtained as to what is 

 meant by the terms chemical and physical properties of 

 elements and compounds. Each element and compound 

 has its own characteristic properties, which are different 

 in a number of ways from those of other elements and 

 compounds. The physical properties of a substance in- 

 clude : 



1. Former state of the material, as solid, liquid, or 

 gas, which depends upon the temperature to which the 

 substance is subjected. Many substances which are solid 

 under ordinary conditions are, at higher temperatures, 

 converted into liquids or vapors ; and substances which 

 are gases are in turn converted into liquids and solids at 

 low temperature and under high pressure. 



2. Weight or specific gravity. The weight or specific 

 gravity of a material depends upon its molecular struc- 

 ture and upon the character of its individual molecules. 

 Some of the elements and compounds have molecules of 

 greater weight than have others. Liquids and gases are 

 characterized as light or heavy according to their weight, 

 compared with some material taken as the standard. 



3. Color. The color of a compound is a physical prop- 

 erty which is due to its chemical composition. Many of 



