CHAPTER III 

 EFFECT OF HEAT ON MATTER 



Effect of heat on solids. One of the best known 

 effects of heat is the change which it causes in the 

 size of a substance. As stated in the preceding chapter 

 a metal ball, which, when cool, slips through a metal 

 ring, will not do so when heated. The ball increases 

 in size when heated. If the ring be correspondingly 

 heated, it becomes so enlarged that the heated ball will 

 pass through it. 



If the ring is cooled, the ball will not pass through it. 

 The ring has decreased in size. If the ball is sufficiently 

 cooled, it will pass through the ring as it did in the 

 beginning of the experiment. 



Telegraph and telephone wires, which in winter 

 are stretched taut from pole to pole, sag in summer, 

 because they become longer. If the wires were 

 stretched taut in the summer, they would snap and 

 break in the winter, because there would not be suffi- 

 cient slack to allow them to contract when cooled. 



When railroad and street car rails are laid in winter, 

 allowance must be made for their expansion in the 

 summer. 



The tire of a wagon wheel is made slightly smaller 

 than the wheel. It is then put into a very hot furnace 



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