42 ANSWERS TO PRACTICAL QUESTIONS 



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, when 

 snow and ice are melting ? 



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

 from all surrounding objects. 



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

 wooden vessel, and the cream in a tin one ? 



The non-conducting wooden vessel prevents the ice from 

 absorbing heat from the external air, and the conducting tin 

 vessel enables it to absorb the heat from the cream. 



1 7. Why does the temperature generally moderate when the 

 snow falls ? 



The vapor passing into the solid form gives off heat. 



19. Why does sprinkling a floor with water cool the air? 

 The water turning to vapor absorbs heat. 



20. How low a degree of temperature can be reached with 

 a mercurial thermometer ? 



Nearly to the freezing point of mercury, 39 F. 



21. If the temperature be 70 F., what is it C. f 



70*- 32'=38. S8-*-1.8=21.r C. 

 If the temperature be 70 C., what is it F. ? 

 70* x 1.8=126*. 126" +32=158* P. 



22. Will dew form on an iron bridge f 

 Yes, because iron is a good radiator. 

 On a wooden brid&tt f 



Not so readily, because wood is a poorer radiator. 



23. Why will not corn pop when very dry ? 



The pores shrink, and the corn becomes compact; only 

 porous, tender-celled corn will pop. 



24. The interior of the earth being a melted mass, why do 

 we get the coldest water from a deep well? 



