Science doesn't stop during the holidays and one of the things we do in chemistry to remind students that chemistry is all around is to make Christmas Ornaments using Chemistry - specifically chemical reactions involving acid and plating metal with acidified metal ions.
We start off with some galvanized iron, which is just iron coated with zinc. The zinc used to protect the iron (or steel) from rusting. Hydrochloric acid will dissolve the zinc from the top of the metal, exposing the iron. The iron will then be coated with copper to make the copper and silver looking ornament.
How to make a Christmas Tree Ornament using Hydrochloric Acid and Galvanized Metal
Cut the metal into any shape you'd like (we cut 2.5 inch squares)
Cover both sides completely with masking tape
Draw a design on the tape or trace a design
Cut out the design using an X-acto knife or utility knife
Remove tape in areas you want to be copper colored when finished; leave tape in areas you want to remain shiny silver color.
Set the metal ornament in a 6 Molar hydrochloric acid bath (3 Molar will work but will take longer). [Muriatic Acid is an acceptable substitute and is available at many hardware stores]
Carefully remove using tongs or tweezers
Rinse with water (distilled water if available)
Completely coat the exposed areas (areas with no tape) with Acidified Copper(II) Nitrate by brushing the solution on with a cotton swab
Allow to dry
Remove the tape
Punch a hold in the metal with a metal punch or using a nail and hammer
Attach a hook or bent paper clip
Zinc reacts with hydrochloric acid causing zinc chloride and hydrogen gas to form (caution: hydrogen gas is highly reactive and flammable!)
Zn(s) + 2HCl(aq) -> ZnCl2(aq) + H2(g)
Iron reacts with acidified copper(II) nitrate which deposits a thin layer of copper on the zinc. This is called metal plating.
Fe(s) + Cu(NO3)2(aq) -> Fe(NO3)2(aq) + Cu(s)