128 



Domestic Science 



through slits made near the ends of long strips of ruled 

 paper, as indicated in Fig. 36. 



Place the two flasks, thus prepared, side by side 

 in the same vessel of water. Mark the positions of the 

 liquid surfaces on the strips of paper. Gently heat the 

 containing vessel and watch the behaviour of the liquid 

 levels, marking the height to which each level attains 

 when the alcohol, which will be noted as rising the 

 faster, has nearly reached the top of the paper strip. 

 The marking may be done most satisfactorily if the 

 burner be withdrawn a short time before the alcohol 

 rises to this height, and the water in the outer vessel 

 be well stirred. Allow the whole apparatus to cool 

 down, when it will be found that, after some time, the 

 liquids regain then 1 former levels (approximately). 



In accordance with our previous observations with 

 regard to the behaviour of solids when 

 heated, the glass flasks will increase in 

 size when heated. The liquids, however, 

 increase to a much greater extent, and 

 hence we are enabled to distinguish 

 clearly the fact of their increase in bulk, 

 in spite of the augmented capacity of the 

 flasks. 



Exercise for Student. 



If the movement of the water-level in the 

 above experiment be watched with great care, it 

 is seen to fall slightly before the rise already men- 

 tioned. Why ? 



84. Another easy experiment will be 

 sufficient to supply us with information 

 concerning the effect of heat upon the Fi &- 37 - 

 volume of a gas. 



