The Composition of Matter 31 



particles of water, of sugar, and of the material from coffee that 

 gives flavor. These are all distributed in this mixture, but do not 

 unite to form a new substance. Each keeps its own properties. 



Air is a mixture made up of four or more kinds of gases. 

 Oxygen, nitrogen, carbon dioxide and water vapor all exist in 

 air as separate gases, but they do not unite chemically to form a 

 new substance. 



Water. Water is a most important inorganic compound 

 and should receive special attention. It is made up of particles 

 of hydrogen and oxygen which have united to form the new sub- 

 stance. Water in a pure state is tasteless and odorless. It will 

 not burn. It is a solvent ; that is, it has the power of dissolving 

 many solids. These, when placed in water, apparently disappear, 

 but really are only changed to a liquid form and are said to be 

 held in solution. This ability to hold substances in solution is a 

 most important characteristic of water. 



It is hardly necessary to draw attention to the wide distribu- 

 tion of water, yet water is found in forms and under conditions 

 which may prevent its immediate recognition. Never forget that 

 all living things contain a large proportion of water. All food- 

 stuffs contain water. This may be proved experimentally by col- 

 lecting the water vapor produced when a piece of any foodstuff is 

 heated. 



Carbon Dioxide. Another very important inorganic com- 

 pound is carbon dioxide. This colorless gas is found everywhere 

 in the air. It is formed constantly in burning, in decay, and in 

 the breathing of animals, and is then spread or diffused through 

 the air. It will not burn and does not support combustion. 



Experiments with Carbon Dioxide. 



Preparation of Carbon Dioxide. Put pieces of limestone or 

 marble into a flask and pour hydrochloric acid on them. This will 

 release the carbon dioxide in the limestone. Collect several bot- 

 tlesful of this gas by the use of a bent glass tube passed through 

 the stopper of the flask and arranged as for the collection of 

 oxygen. 



Insert a burning splinter into one bottle and observe the result. 

 Insert other burning substances and observe the results. Pour 



