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How do we differentiate physical changes from chemical changes?

Answer 1

Olivia Anton

Well physical changes are largely changes in state....solid to liquid, liquid to gas etc.

And thus...

#H_2O(l) rarr H_2O(g)# #"vaporization..."#

#H_2O(s) rarr H_2O(l)# #"melting..."#

#H_2O(g) rarr H_2O(l)# #"condensation..."#

#CO_2(s) rarr CO_2(g)# #"sublimation..."#

#CO_2(g) rarr CO_2(s)# #"deposition..."#

Whereas chemical change involves the formation of new substances and the making and breaking of strong chemical bonds....

#CH_4(g) + 2O_2(g) rarr CO_2(g) + 2H_2O(l)#

#2Fe(s) + 3/2O_2(g) rarr Fe_2O_3(s)#

#Ag^+ +Cl^(-) rarr AgCl(s)darr#

#Na(g) + 1/2Cl_2(g) rarr NaCl(s)#

#NaCl(s) stackrel(H_2O)rarrNa^+ + Cl^-#

The last example will be controversial, but strong chemical bonds have been broken, and strong chemical bonds have been formed in the solution...that the reaction is reversible is immaterial to the definition.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.