EFFECT OF VARYING TEMPERATURES ON WATER 137 



rapidly, and the change of state increases its volume more 

 than 1700 times. It is this stupendous pressure of rapidly 

 generating water- vapor that is " harnessed " in the steam 

 engine. This is one of the most marvelous manifestations 

 of the energy of heat. 



Experiment 57. Fill a flask of about 500 cc. with water. Press 

 into the mouth of the flask a rubber stopper through which a glass 

 tube about 30 cm. long extends. The tube should be open at both 

 ends and should not extend into the flask below the bottom of the 

 cork. When the cork is pressed in, the water will be forced up 

 into the tube for several centimeters. See that the 

 cork is tight and that there are no bubbles of air in the 

 flask or tube. 



Now place the flask for fifteen or twenty minutes in 

 a mixture of ice and water (Figure 72) and carefully 

 mark with a rubber band the point at which the water 

 in the tube comes to rest. Take the flask out of the 

 freezing mixture and notice immediately whether the 

 water in the tube rises or falls. Continue for five or FIGURE 72 

 ten minutes to notice the action of the water in the 

 tube. The volume of the water is not the least when it is at the 

 temperature of melting ice, 32 F., but when it is a little above 

 this temperature. 



Experiment 58. Put a piece of ice in water. What part of its 

 volume sinks below the surface of the water ? Is it heavier or lighter 

 than water? From Experiment 32 do you conclude that cold 

 water is heavier or lighter than warm water? 



When water at ordinary temperatures is cooled it contracts 

 and grows denser. It continues to do this until the whole 

 body of water reaches a temperature of about 4 C. Here 

 a remarkable change takes place ; for as water is cooled below 

 this point it expands. This expansion goes on until the 

 liquid turns to solid at C. 



At the moment water solidifies into ice, it expands with 



