134 



ELEMENTARY GENERAL SCIENCE 



CHAP. 



expansion, expansion in area or superficial expansion, and ex- 

 pansion in volume or cubical expansion. In the case of liquids 

 and gases we are concerned only with their cubical expansion. 



2. Change of temperature, of course, means simply that the 

 effect of an addition of heat is to make the body get hotter and 

 hotter, while a subtraction causes it to become colder and colder. 



3. Change of state includes changes in the physical condition 

 known as liquefaction or becoming liquid, and vaporisation or 

 becoming converted into vapour. Thus, if we heat ice it first 

 liquefies or becomes water, and is then vaporised or becomes 

 steam. 



CHANGE OF SIZE. 



Expansion. EXPT. 125. Take a metal ball suspended by 

 a chain as shown in the figure, and suspend it by the side of a 



FIG. 53. The Expansion of a Solid. FIG. 54. The expansion of a Liquid. 



metal ring, through which it passes easily, or fits loosely. 

 Heat the ball in a laboratory burner for a few minutes, and 

 then try to drop it through the ring. It is too large and rests 

 on the ring. Now allow it to cool slowly and notice that after 

 a short time it gets smaller and will slip through quite easily. 

 EXPT. 126. Procure a 4 oz. flask and fit it with a cork. 

 Bore a hole through the cork and pass through a long glass 

 tube whicli fits tightly. Fill the flask with water coloured 

 with red ink. Push the cork into the neck of the flask and so 

 cause the coloured water to rise up the tube. See that there 



