AN INTRODUCTION TO SCIENCE 



CHAPTER I 

 HEAT 



Value of fire. Every day, uncontrolled fire wipes out human 

 lives and destroys vast amounts of property; every day, fire, 

 controlled and regulated in stove and furnace, cooks our food 

 and warms our houses. Fire melts ore and allows the forging 

 of iron, as in the blacksmith's shop, and the fashioning of 

 innumerable objects serviceable to man. Heated boilers change 

 water into the steam which drives our engines on land and sea. 

 Heat causes rain and wind, fog and cloud ; heat enables vegeta- 

 tion to grow and thus indirectly provides our food. Whether 

 heat comes directly from the sun or from artificial sources such 

 as coal, wood, oil, or electricity, it is vitally connected with our 

 daily life, and the facts and theories relative to it are among the 

 most important that can be studied. 



General effect of heat. Expansion and contraction. One of 

 the best-known effects of heat is the change which it causes in 

 the size of a body. Every housewife knows that when a kettle 

 is filled with cold water and heated, there is an overflow as 

 soon as the water becomes hot. Heat causes not only water, 

 but all other liquids, to occupy more space, or to expand, and in 

 some cases the expansion, or increase in size, is surprisingly 

 large. If 100 pints of ice water, for example, are heated in a 

 kettle, the 100 pints steadily expand until, at the boiling point, 

 they occupy as much space as 104 pints of ice water. 



The expansion of water can be easily shown by heating a 



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