EFFECTS OF HEAT 



115 



finally escapes by explosion. In some cases the explosions are of 

 great force. 



A very high degree of heat is required to pop corn in a satis- 

 factory manner. This causes most of the cells to explode simul- 

 taneously. The grains of the corn are literally turned inside out, 

 and are transformed into a relatively large mass of snow-white starch. 



Why Ice Floats. When water becomes warmer than 39 it 

 will rise to the top of a lake because it has also become lighter. This 



Boiling water at 212 F. weighs 59.7 Ibs. per cu. ft. 

 Water at 32 F. weighs 62.4 Ibs. per cu. ft. 



Ice at 32 F. weighs 57.5 Ibs. per cu. ft. 



WATER SINKS 

 AS ITS TEMP. FALLS 



TEMP. OF WATER 

 RISING ABOVE 

 39%* CAUSES 

 WATER TO RISE 



WATER COOLING 

 TQ 39%' F. SINKS 



WATER RISES AS 

 THE TEMP DROPS 

 BELOW 39 2 /s F. 



WATER IS AS HEAVY AS IJ CAN GET 



AT39 2 /s'F. 



FIG. 89. Why would ice float in boiling water? What is the difference between 

 the weight of ice at 32 F. and water at 32 F.? At what temperatures is 

 water the lightest? At what other temperature is the weight of water about 

 the same as that of boiling water ? 



