HEAT 



S5 



Heat Expands Solids. 

 The question may now be asked of the 

 pupils: Does heat expand solids? They will 

 be ready to say that they think that it does, 

 and now comes the opportunity of having 

 them devise a means of proving it. If, un- 

 aided, anj'one of the class can invent such 

 apparatus the results will be excellent. The 

 following are some simple forms of appa- 

 ratus used to illustrate expansion of solids. 

 A metal ball just passing through a metal 

 ring at the ordinary temperature of the 

 room will not pass when heated, and will 

 pass more readily when the ring is heated. 

 An iron or other metal bolt nicely fitting 

 into a hole in another piece of metal may 

 be used in the same way. A simple appara- 

 tus can be made which will show expansion 

 in rods of various metals, or of various forms 

 such as poker, stove lid, gas pipe, etc. Two 

 heavy blocks of wood are used to support 

 the object. Into the top of one block a nail 

 is driven projecting above the top of the 

 block. One end of the object (iron poker for 

 example) is supported by this block, the end 

 of the poker being pushed firmly against the 

 projecting nail, the other end of the poker is 

 supported by the other block, the end pro- 

 jecting beyond the block. When the poker 

 is heated the strip prevents the expanding 

 poker from pushing in that direction, thus 

 the whole of the movement is shown at the 





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Fig". .^5 Apparatus for 

 -^howirjg exptinsiou of 

 a metal rod by heat. 



