38 CHEMICAL ACTION. 



gas, the air is again disturbed, as it 

 would be by the explosion of gunpowder. 



Q. How does fore condense HYDROGEN and 



OXYGEN into WATER ? 



A. The hydrogen of fuel and oxygen 

 of air (liberated by combustion) combi- 

 ning together, condense into water. 



Q How does fore expand CARBON into 



CARBONIC ACID GAS ? 



A. The carbon of fuel and oxygen 

 of air (combining together in combus- 

 tion) expand into a gas, called carbonic 

 acid. 



Q. Why is a FIRE (after it has been long 

 burning) RED HOT? 



A. When coals are heated through- 

 out, the carbon is so completely mixed 

 with the oxygen of the air, that the whole 

 surface is in a state of combustion, and 

 therefore red hot. 



Q. In a BLAZING fore, why is the UPPER 

 surface of the COALS BLACK, and the LOWER sur- 

 face RED ? 



A. Carbon (being very solid) requires 

 a great degree of heat to make it unite 

 with the oxygen of the air. When fresh 



