when zinc sulfate is added to a piece of copper-no chemical changes are observed, and no chemical reactions occur- why?
This has to do with something called electronegativity. Zinc is less electronegative than Copper, which means that it likes to give up its electrons more readily than Copper (or conversely, Copper likes to hang on to electrons more strongly than Zinc). Therefore no reaction occurs because that would require the Zinc ions in solution to pull the electrons away from the neutral Copper atoms, and it is not electronegative enough to do so. If you reversed this however, and added copper sulfate to zinc, a reaction would proceed in which the copper grabbed the electrons away from the neutral zinc atoms to precipitate out copper atoms and produce zinc ions. Hope this helps.
Basically a Physical change is something that you can do something to the product and get the reactants again, usually creates one product. A chemical change is something that you can not get the reactants back from the product, and can produce more than one products.
