52 ANSWERS TO PRACTICAL QUESTIONS 



10. Ought an inkstand to have a large or a small 

 mouth ? 



A small mouth, to prevent evaporation. 



11. Why is there a space left between the ends of the 

 rails on a railroad trade ? 



To allow room for the expansion and contraction of the 

 rails with the changes in temperature. 



12. Why is a person liable to take cold when Jiis clothes 

 are damp? 



The water which evaporates from his clothes, in drying, ab- 

 sorbs heat from his body. 



13. What is the theory of corn-popping ? 



The air in the cells of the corn expands by the heat, and 

 bursts the outer coating of the corn. 



14. Could vacuum-pans be employed in cooking ? 



They could not, because the heat would not be sufficient to 

 cook the food. 



15. Why does the air feel so chilly, in the spring, ivhen 

 snow and ice are melting ? 



When the ice is passing into the liquid state, it absorbs heat 

 from all surrounding objects. 



1(>. Why, in freezing ice-cream, do we put the ice in a 

 ivooden vessel, and the cream in a tin one ? 



The non-conducting wooden vessel prevents the ice from ab- 

 sorbing heat from the external air, and the conducting tin ves- 

 sel enables it to absorb the heat from the cream. 



17. Wliy does the temperature generally moderate 

 when the snoiv falls ? 



The vapor passing into the solid form gives off heat. 



19. Why does sprinkling a floor ivith ivater cool the 

 air? 



The water turning to vapor absorbs heat. 



