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HOW WE USE HEAT 



In how many ways is heat energy used in the kitchen ? 



heat is added to ice at 32 to melt it, the resulting water 

 also is at 32 F. There is no change in temperature when 

 ice melts or when water freezes. Water boils and steam 

 condenses at sea level at 212 F. During this change of 



state there is no change in tem- 

 perature. 



Demonstration 5. Boiling Water. 



1. Constant Temperature of Steam 

 and Boiling Water in Open Vessel. 

 Heat water in a flask. Have two 

 thermometers, one placed so that the 

 bulb is in water and the other so 

 that it will be in the steam above 

 the water. After the water is boil- 

 ing, read the thermometers at inter- 

 vals of one minute for five minutes. 

 Tabulate your results. What are your conclusions? 



2. Boiling Water at Reduced Pressure. A ring-neck, heavy- 

 walled, round-bottom flask is filled half full of water. Boil the 



