CHAPTER VII 



PHYSICAL AND CHEMICAL CHANGES 



Physical change. Matter may undergo many 

 changes. One class of these changes is not accom- 

 panied by any alteration in the composition of matter. 

 When a piece of glass is broken the small pieces do 

 not differ from the original piece except in size. A 

 piece of iron may be broken, it may be magnetized, 

 it may be heated, it may be melted, and it may be 

 converted into a vapor. In none of these changes, how- 

 ever, has the composition of the iron been affected. 

 The pieces of iron, the magnetized iron, the heated 

 iron, the melted iron, or the iron vapor are just as 

 truly iron as was the original piece. Sugar may be 

 dissolved in water, but neither the sugar nor the water 

 is changed in composition. The resulting liquid has 

 the sweet taste of sugar, but the water can be evap- 

 orated by heating and the sugar recovered unchanged. 

 Such changes are called physical changes. Physical 

 changes are those which do not involve a change in the 

 composition of substances. In other words, a physical 

 change is a change in the form but not in the nature 

 of a substance. 



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