In this video we turn copper pennies into silver and finally to gold. Obviously it's a chemistry trick but still impressive. First we get 30g of zinc sulfate and dissolve it into 100mL of water. Zinc sulfate was made back in our video on making a copper sulfate and zinc battery: If you don't have zinc sulfate or can't make it, you can also use zinc chloride. This can be made by simply mixing hydrochloric acid with zinc metal and waiting until the fizzing stops. Then we drop in several cut strips of zinc metal. Zinc metal was obtained from our video on getting useful materials from batteries: www.youtube.comis heated to a boil and copper pennies, that have been thoroughly washed/cleaned, are dropped in. They must touch the zinc in order for this reaction to work. Leave it in for five to ten minutes. The zinc metal dissolves and releases electrons that go into the copper and give it a negative charge. The zinc ions in solution now redeposit form a thin layer of zinc metal. Giving the coin a silvery color. Now the smart physical chemist might wonder how this can possibly work. Overall we're going from zinc metal to zinc metal and at first it seems like we're missing something about thermodynamics. What is the driving force? I've searched the literature and there doesn't seem to be a consensus among scientists, some claim it's a surface free energy issue with zinc having a lower potential on copper than in free solution (at high concentration <b>...</b>
Read more other entries :
