*digs through a crapload of old chem notes from last term* Ahh, here we go. ^__^ This shows you how to turn a penny gold, enjoy~ (Note: It's not real gold, it's just a brass alloy that resembles it)
Materials: Forceps, a couple a pennies (other coins won't work), zinc powder, sodium hydroxide (NaOH), bunsen burner, ceramic evaporating dish (the one we used held approximately 45 mL, I'm guessing >_>), 10 mL graduated cylinder, flint striker, paper towel, goggles, and a ring stand and clamp
Procedure: Place about 5 grams of zinc powder in the evaporating dish. Add enough NaOH to cover the zinc powder and fill the dish one-third full. (it was about 15 mL when we did it) Attach ring to stand with clamp and set dish in it, place bunsen burner directly beneath the dish, and start it with the flint striker.
Heat to near boiling point, but be careful not to let it burn you. You also want to keep a good distance and be careful not to let the vapors get near you or breathe them in - it's a very strong base and could cause serious skin and lung damage. o-o; Not fun.
Place a clean penny into the solution (you can only do one at a time) with a pair of forceps. Allow the penny to soak in the solution for 3-4 minutes. Be sure that the solution covers the penny. Remove it after the time has passed, rinse it with running water from a sink to remove excess solution, and blot it dry with a paper towel. The penny will be VERY HOT, so be careful. At this stage, it has turned a bright silver colour - you can leave it like that if you want, or if you want it to turn gold, follow the next steps.
Using the forceps, hold the penny in the bunsen burner flame for 5-10 seconds (but not too long, or it'll melt). Rinse penny again under running water, blot dry - again it'll be very hot, so be cautious - and voila!
You can use the same solution over again a few times with more pennies; my group made about 5 or 6 pennies and it worked fine. I would strongly reccomend *not* doing this at home; ask your high school or college professor if you can use the chemistry lab to do this sometime, or you could even show it to the class and convince them to make a project out of it. :3 Hope you enjoy.
If you do opt to perform this experiment at home (which you really, really shouldn't unless your dad is like Hoho-papa and has a lab in the house XD), I hold no responsibility for singed cats, burned drapery, rooms filled with toxic vapors, burns, disgruntled parents, or other misfortunes. >>;