EXPANSION AND CONTRACTION OF AIR 25 



a. Have a flask fitted with a one-hole stopper and a glass tube 

 as shown in Fig. 14. Fill the flask with water, and press the 

 stopper tightly into it; the water will rise part way up the 

 tube. Mark the level of the water in the tube by means of a 

 strip of gummed paper or a thread; then dry the flask 



and put it on wire gauze placed on a ring stand. 



Heat the flask carefully with a small flame. Note 

 all the changes that occur in the water level, and 

 explain them. Do not heat the water to boiling, 

 or until it actually overflows. 



Let the flask cool, and then put it into a dish of 

 cold water, or hold it under a cold-water faucet. 

 What happens? 



b. Instead of heating the flask over a flame you 

 can plunge it into a pail of hot water. Note the 



first effect upon the level of the water, and the effect as heat- 

 ing is continued. Explain each effect. 



c. Simpler Form. Instead of a flask you can use a bottle 

 with a long neck, such as a household-ammonia bottle, or a 

 vinegar bottle. No stopper or tube will be needed. Mark 

 the level of the water carefully (it should be a few centimeters 

 below the mouth of the bottle), put the bottle in a pail of water, 

 and heat the water in the pail; or you can set the bottle in a 

 warm place, as, for example, near a radiator or a stove, for an 

 hour or two. Note the change (or changes) in the level of the 

 water, and explain. Then let the bottle cool, and note the 

 results. If possible, set it in a cold place, but do not let it freeze. 



EXERCISE 21 

 EXPANSION AND CONTRACTION OF AIR 



Apparatus and Materials. Flask or small-mouth bottle, pan of 

 water, drinking glass, saucer. 



