308 Common Science 



sulfur and light it, and then plunge it into the bottle, you 

 will see iron burn. 



Both manganese dioxid and potassium chlorate have 

 a great deal of oxygen bound up in them. When they 

 join together, as they do when you heat them, they 

 cannot hold so much oxygen, and it escapes as a gas. 

 In the experiment, the escaping oxygen passed through 

 the tube, filled the bottle, and forced the water out. 



What burning is. When anything burns, it is simply 

 joining oxygen. When a thing burns in air, it cannot 

 join the oxygen of the air very fast, for every quart of 

 oxygen in the air is diluted with a gallon of a gas called 

 nitrogen. Nitrogen will not burn and it will not help 

 anything else to burn. But when you have pure oxygen, 

 as in the bottle, the particles of wood or charcoal or 

 picture wire can join it easily ; so there is a very bright 

 blaze. 



Although free oxygen helps things to burn so bril- 

 liantly, a match applied to the solids from which you got 

 it would go out. And while hydrogen burns very easily, 

 you cannot burn water although it is two-thirds hydro- 

 gen. Water is H 2 O, you remember. 



What compounds are. When elements are combined 

 with other elements, the new substances that are formed 

 are called compounds. Water (H 2 O) is a compound, 

 because it is made of hydrogen and oxygen combined. 



When elements unite to form compounds, they lose 

 their original qualities. The oxygen in water will not 

 let things burn in it ; the hydrogen in water will not 

 burn. Salt (NaCl) is a compound. It is made of the 

 soft metal sodium (Na), which when placed on water 



