EFFECTS OF HEAT 113 



if possible, in cool places, since there will be a greater expansion of 

 the air when the product is placed in the oven. 



Experiment to Show the Expansion of a Liquid and a Solid. 

 Fill a flask with a red liquid. Close the flask with a one-hole rubber 

 stopper through which extends a 2-foot piece of glass tubing with 

 a very small bore. Place a paper at the top of the liquid in the 

 glass tubing. Heat the liquid very slightly at first by allowing the 

 flame to touch the flask for an instant. The liquid will suddenly 

 drop and then rise. Repeat the heating; the same thing will occur 

 each time. The glass is heated first, and the flask becomes slightly 

 larger. The liquid will drop to fill up the extra space. Why does 

 the liquid go back to the same level, and even higher after heat has 

 been removed? 



Continue to heat the flask for a few moments. The liquid will 

 rise quickly because of its expansion. One hundred pints of water 

 will become 103 pints of water if heated from 39 to boiling point 

 (about 2 12). 



The Expansion and Contraction of Water. Liquids usually 

 expand with heat. Water expands when heated, if it has a tem- 

 perature above 39 F. If, however, the temperature falls below 

 39 F. the water will gradually expand until it freezes at 32. 



The exact weight of 1 cubic foot of water at 62 F. is 62.355 

 pounds or 998f ounces. It is generally taken as 1000 ounces. 

 At a temperature of 52.3 F. 1 cubic foot of water weighs exactly 

 62.4 pounds. 



A gallon of water at 62 F. = 0.1337 cubic feet=231 c\i. in., and weighs 8 

 pounds. One cubic foot of water =7.48 gallons. 



Expansion caused by Water Changing into Steam. When water 

 changes into steam exceptional expansion occurs. One quart of 

 water will become about 1700 quarts of steam. The extra volume 

 creates great pressure which is utilized for running engines in 

 locomotives, steamboats, etc. 



Why Corn Pops. A kernel of popcorn is filled with starch grains. 

 The interior of the kernel is divided into a large number of cells. 

 The walls of these cells are sufficiently strong to withstand con- 

 siderable pressure from within. Upon the application of heat, the 

 moisture present in each little, cell is converted into steam, and 



