48 INTRODUCTION TO GENERAL SCIENCE 



ably below the freezing point of water. Carbon dioxide may 

 be obtained in liquid form in steel tanks. If this liquid is 

 allowed to expand, so much heat is required that it turns to a 

 white solid at a temperature of 80 C. Mercury may be 

 frozen by the removal of the heat required to evaporate 

 solid carbon dioxide. 



References : 



1. 1002 : 393-395. Heat of Sun Due to its Contraction. 



2. 1103:49-50. Heating by Compression and Cooling by 



Expansion in the Atmosphere. 



3. 1803 : 176. Heat Developed by Friction. 



4. 1803 : 177-178. Heat Produced by the Compression of a 



Gas. 



5. 1803 : 178-179. Cooling by Expansion. 



6. 1803 : 210. Intense Cold by Evaporation and Ex- 



pansion. 



a. 1805 : 307-309. Heat Produced by Friction and by Com- 

 pression. 



6. 1807 : 161-162. Heat from Friction. 



c. 1808 : 214-215. Friction and Compression as Sources of 

 Heat. 



EXPERIMENTS FOR THE HOME 



Rub a coin on the coat sleeve; hammer a piece of lead. 

 Notice that a bicycle pump becomes warm, during use, and 

 note that the connecting tube also is heated. 



Try to obtain a lead bullet immediately after it has struck 

 an iron target, and note its appearance as well as its tempera- 

 ture. Explain its appearance. Why would the results not 

 be the same with a wooden target ? 



Observe that in all of the given examples motion has been 

 changed into heat, that is, molar or mass motion is trans- 

 formed into molecular motion. 



