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Are chemical changes easily reversed by altering the temperature of the system? Are they associated primarily with extensive properties? Are...

Chemical changes involve a change in the chemical composition of the material/s involved. Physical changes, on the other hand, do not include any change in the chemical composition of the material. A phase change is a common example of a physical change. A chemical reaction (say, oxidation, hydrolysis, etc.) is a common example of chemical change. 


Let us take a look at each statement, one by one.


A change in temperature causes phase change, which is a physical change. An increase in temperature causes a solid substance to melt and a liquid to vaporize. Since the chemical composition is the same, it is not a chemical change; statement A is not correct.


Extensive properties are those that are dependent on the size or quantity of the material. Examples of extensive properties are mass, volume, length, etc. Physical properties are independent of the extensive properties. 1 gm of water vaporizes at 100 degrees C, as does 1 l of water. Similarly, chemical changes can also be independent of extensive properties. Chemical reactions take place in stoichiometric ratios. Hence statements B and C are also not correct.


There are other ways of identifying a substance, such as by examining physical properties. Hence statement D is incorrect.


Thus, among the given options, all the statements are incorrect.


Some correct statements could be: physical changes may be reversed by changing the temperature. Chemical changes always produce substances different from the starting substances.


Hope this helps. 

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