MATTER AND ITS PROPERTIES 27 



While man has succeeded in combining a number of 

 elements, or fundamental substances, in supposedly new 

 ways to form many new compounds, yet all these sub- 

 stances that man has been working with have existed 

 in some form since the very beginning of time. We 

 have found a number of elemental things on the earth, 

 but the number is not so large as might be supposed, for 

 while we have several hundred thousand different com- 

 pound substances they are all composed of combinations 

 of about eighty elements. 



A few of these fundamental substances are well known 

 to us, such as iron, lead, zinc, copper, tin, aluminum, 

 mercury, nickel, silver, gold, and platinum among the 

 metals ; oxygen, hydrogen, and nitrogen among the gases, 

 and carbon, which does not belong with either the metals 

 or the gases. Our bodies are composed chiefly of carbon 

 and three of these gases oxygen, hydrogen, and nitrogen. 



We might think at first that if we knew the properties 

 of each of the elements, it would be quite easy to predict 

 the properties of each of the compounds of these same ele- 

 ments. This, however, is far from being the case. As the 

 elements combine, they lose their individuality entirely. 

 For example, if we combine oxygen and hydrogen, two 

 gases, we have water, very different in appearance and 

 different in all its properties (cf. p. 94). 



Just how the elements differ from one another is hard 

 to tell. All the elements are composed of extremely 

 small particles, called atoms. Atoms are so very small 

 that they cannot be seen with the most powerful micro- 

 scopes that have been made. There are just as many 

 different kinds of atoms as there are elemental substances. 

 We use a different term to designate the particles formed 

 when two or more of these atoms unite. We do not 



