Common Science 



FIG. 44. When the wire is cold, it is fairly tight. 



Experiment 28. Fill a flask to the top with water. Put a 

 piece of glass tubing through a stopper, letting the tube 

 stick 8 or 10 inches above the top of the stopper. Put the 

 stopper into the flask, keeping out all air; the water may 

 rise 2 or 3 inches in the glass tube. Dry the flask on the 

 outside and put it on a screen on the stove or ring stand, 

 and heat it. Watch the water in the tube. What effect 

 does heat have on the water ? 



Here are two interesting experiments that show how 

 solid things expand when they are heated : 



Experiment 29. The brass ball and brass ring shown in 

 Figure 43 are called the expansion ball and ring. Try 

 pushing the ball through the ring. Now heat the ball over 

 the flame for a minute or two it should not be red hot 

 and try again to pass it through the ring. 



Heat both ball and ring for a short time. Does heating 

 expand the ring? 



Experiment 30. Go to the electric apparatus (described 

 on page 379) and turn on the switch that lets the electricity 

 flow through the long resistance wire. Watch the wire as 

 it becomes hot. 



Application 24. A woman brought me a glass-stoppered 

 bottle of smelling salts and asked me if I could open it. 



