50 PROPERTIES AND MAKE-UP OF MATTER 



nized by the odor. Yet nothing can in any possible way be 

 seen to have been added to the air. 



Experiment 14. Dip a glass rod in strong hydrochloric acid 

 and hold it a few inches above the open mouth of a bottle of strong 

 ammonia water. Nothing can be seen to be emitted from either 

 the rod or the bottle, but when they are brought near together a 

 cloud of little white particles is formed. This must be due to the 

 action of an invisible something which came from the ammonia 

 upon an invisible something which came 

 from the hydrochloric acid, resulting in the 

 formation of something that is visible. 



Molecules are too small to be seen 

 by the most powerful microscope. 

 There are millions of them in a par- 

 ticle of matter as big as the head of a 

 pin. Some one has said that if a drop 

 FIGURE 20 f water could be magnified to the size 



of the earth, the molecules would 

 probably appear no larger than a baseball. 



It has been found possible by chemical and electrical 

 means to divide molecules into smaller particles called 

 atoms, and very recently to find out something about the 

 composition of the atoms themselves. For example, the 

 smallest particle in which water can exist and still be water 

 is a molecule. By means of an electric current these mole- 

 cules can be broken up. But when we thus divide the 

 molecules of water we no longer have water; we have two 

 gases, hydrogen and oxygen. 



Experiment 15. (Teacher's Experiment). Procure from the 

 chemical laboratory an electrolysis apparatus or arrange an ap- 

 paratus as shown in Figure 21. This consists of a glass dish partly 

 filled with water to which a little sulphuric acid has been added. 

 (The sulphuric acid is needed only to aid in carrying the electricity 



