Chemical Change and Energy 305 



FIG. 164. Trying to se.e if hydrogen will burn. 



Getting oxygen, a gas, from two solids. Oxygen (0) 

 can hide just as successfully as hydrogen. Practically 

 all elements can do the same by combining with others. 

 Here is an experiment in which you can get the gas, 

 oxygen, out of a couple of solids. If you went to the 

 moon or some other place where there is no air, you could 

 carry oxygen very conveniently locked up in these solid 

 substances. Oxygen, you remember, is the part of the 

 air that keeps us alive when we breathe it. 



Experiment 93. In a test tube mix about one half tea- 

 spoonful each of white potassium chlorate crystals and black 

 grains of manganese dioxid. Put a piece of glass tubing 

 through a cork so that the tubing will stick down a little 

 way into the test tube. Do not put the glass tubing through 

 the cork while the cork is in the test tube : insert the glass tubing 



