30 CHEMICAL ACTION. 



CHAPTER III. 



Q. What is the third chief source of heat ? 



A. CHEMICAL ACTION. 



Q. What is meant by chemical action being 

 the source of heat ? 



A. Many things, when their chemical 

 constitution is changed, (either by the 

 abstraction of some of their gases, or by the 

 combination of others not before united,) 

 evolve heat, while the change is going on. 



Q. Explain by illustration what you mean. 



A. Water is cold, and sulphuric acid 

 is cold ; but if these two cold liquids be 

 mixed together, they will produce boiling 

 heat. 



Q. Why will COLD WATER, mixed with 

 SULPHURIC ACID, produce heat ? 



A. Because water (being lighter than 

 sulphuric acid), is condensed by the 

 heavier liquid; and its heat is squeezed 

 out, as water from a sponge. 



Q. Why does COLD WATER, poured on LIME, 

 make it intensely HOT ? 



A. The heat is evolved by the 

 chemical action, produced by the cold 

 water combining with the lime. 



