46 INTRODUCTION TO GENERAL SCIENCE 



the other end in the flame. Heat for ten minutes or more 

 Watch the color of the copper strip. Examine the heated end 

 after ten minutes. Bend this end back and forth, and explain 

 what you notice. Give it a name. What makes you think so? 



31. CHEMICAL COMBINATION PRODUCES HEAT 



One form of chemical action was studied in Section 4, 

 Combustion. There we learned that the union of oxygen and 

 some combustible produces a large amount of heat. From 

 the little you have studied of general science, you would 

 expect that any chemical union would produce heat. This 

 is true in all cases where there can be no further chemical 

 change. The heat is not always apparent nor of the same 

 quantity as in the oxidation of substances, but it is quite 

 noticeable in several instances. 



Sulphuric acid and water when poured together form a 

 chemical union which liberates a large quantity of heat. 

 Balloonists make use of this method of obtaining heat without 

 a fire, which would be dangerous. Many of the common 

 metals and acids combine and liberate heat. A gas, hydrogen, 

 is also set free. This gas will be studied in Section 114, 

 Composition of Water. 



References : 



1. 1703 : 220. Heat of Formation and Decomposition. 



a. 1701 : 75-76. Heat of Reaction. 



b. 1704 : 318-319. Thermal Relations of Chemical Changes. 



c. 1705 : 147-150. Heat of Chemical Changes. 



d. 1706:112-113. Heat and Chemical Action. 



e. 1708:117-118. Heat of Chemical Action. 

 /. 1709 : 218-219. Heat of Formation. 



