A YEAE IN SCIENCE 29 



on the punch to which the nut fits. Then heat the nut 

 and adjust it on the punch once more. Does it pass 

 as far or farther on the punch than it did when cold? 

 Heat the punch and repeat the adjustment. What do 

 you find? What does this show? Have you ever seen 

 a blacksmith fit a tire to a wagon wheel? What is 

 the principle involved? 



C. Do all solids expand and contract at the same 

 rate? To determine this, use a compound bar. A 

 compound bar consists of two metals tightly welded or 

 riveted together lengthwise. Heat the bar equally on 

 both sides by playing the flame of a Bunsen burner 

 along its edge. Do you observe any change in the 

 direction of the bar? What does this indicate? Cool 

 the bar by running tap w r ater over its edge. Does the 

 direction of the bar now change ? How do you explain 

 these results? 



Exercise 10. Effect of Heat on Liquids. 

 Object: Does the volume of liquids change with 

 a change in temperature ? 



Apparatus 



Test tube Bunsen burner 



One-hole rubber stopper Test tube clamp 



Glass tube 



Directions : A. Fill the test tube with cold water. 

 Into the mouth of the tube insert the rubber stopper 

 fitted with a glass tube. Press on the stopper until the 

 water rises about an inch in the glass tube. Marli 

 carefully the level of the water. 



