Our Surroundings 



know, the bottle will break, due to the expansion of the water. 

 This explains why water pipes burst and the cement sides of 

 cisterns crack in very cold weather. 



Water increases its volume over one-twelfth when it freezes. 

 The water in a pond or a lake contracts as it cools until it reaches 

 a temperature of 39 degrees F. Then it begins to expand until 

 it reaches the freezing temperature. The ice is lighter than the 

 water and so floats. Otherwise, ice would sink and if cold con- 

 tinued the lake would finally become solid ice. This would make 

 a great change in the climate, and would destroy water life. 

 This expansion is not true of most other liquids, as they continue 

 to contract as they cool until they become solid. 



Experiments to Show the Expansion of Three States of 

 Matter by Heat. 1. To show that a solid will expand when 

 heated, take a metal ball and a ring through which the ball will 

 just pass when cool. Heat the ball and try to pass it through the 

 ring. Explain the result. 



2. To show that a liquid expands when heated, fill a large 

 bottle with colored water. Insert through the center of a cork a 

 glass tube about ten inches long until one end is level with the 

 lowest part of the cork. Put the cork tightly in the mouth of the 

 bottle and then push the tube down about an inch lower into the 

 water. Heat the bottle gently over a Bunsen burner and observe 

 the effect on the water. At first the height of the water in the bot- 

 tle becomes a little less. Can you account for this? Afterwards, 

 the water gradually rises and some passes up the tube, showing 

 that water expands when it is heated. 



3. To show that gas expands, heat water in a tea kettle and 

 notice that as the water boils the cover of the kettle, if set loosely, 

 bobs up and down, and steam escapes. Steam is a gas. As it 

 rises from the water it expands and exerts a pressure which 

 lifts the cover and allows some of the steam to escape ; when the 

 pressure is released the cover drops back. This is another illus- 

 tration of heat transformed into motion. 



Variation of the Boiling Temperature. The boiling tem- 

 perature of a liquid is reached when the motion of the mole- 

 cules within the liquid becomes so great that they get far enough 



