EXPANSION OF GLASS. 125 



A. Heat expands the metal ; and as 

 the metal is increased in bulk, it occupies 

 a larger space, (or, in other words, rises 

 higher in the tube.) 



Q. Wtiy is a GLASS BROKEN, when HOT WATER 

 is poured into it ? 



A. Because the inside of the glass 

 is expanded by the hot water, and not 

 the outside ; so the glass snaps for want 

 pf flexibility. 



Q. Why is not the OUTSIDE of the GLASS 

 expanded by the hot water, as well as the INSIDE ? 



A. Glass is a non-conductor of heat ; 

 and, therefore, breaks before the heat of the 

 inner surface is conducted to the outside. 



Q. Why does a GLASS snap, because the INNER 

 surface is HOTTER than the OUTER ? 



A. Glass is expanded by heat ; and as 

 the inner surface expands, it stretches the 

 outer surface till it snaps. 



Q. Why is a CHINA CUP broken, if HOT 

 -WATER be poured over it, or into it ? 



A. China is a non-conductor ; and, as 

 the inner surface expands by the heat, 

 before the outer one, it forms an arch, 

 and pulls the parts of the cup asunder. 



M 3 



