At the completion of this lab, students will be able to write and balance the reactions that are occurring and explain why the solutions have changed colors (HCl goes from colorless to yellow and CuSO4 goes from dark blue to light blue).
This activity is not only a good activity to reinforce various topics, but also can be used as a springboard into several other topics. Other topics that can be covered are:
1. Types of reactions
4. Activity series and predicting if whether or not a reaction will occur.
5. Balancing reactions and predicting the products.
6. Practicing safe procedures and reinforcing the use of the MSDS information
7. Ionic reactions, net ionic reactions, and spectator ions
Age/Level of participants:
This activity is geared towards high school (or college) chemistry students, roughly 15 years and older. Students must be carefully supervised at ALL times.
I personally have my students read the MSDS information of each substance and then discuss what safety precautions must be taken, what to do in the event of an emergency, and what can be done to minimize the chances of an accident prior to doing the lab.
Material Safety Data Sheet information (MSDS):
Search for concentrated hydrochloric acid
Search for copper (II) sulfate (also called cupric sulfate) OR copper (II) nitrate (also called cupric nitrate)
The ornament will be made from a piece of galvanized iron. Galvanized iron is iron coated with a thick layer of zinc. The zinc layer prevents the iron from corroding.
In this experiment, we will remove the zinc layer by dissolving it in hydrochloric acid.
Zn (s) + 2 HCl (aq) --> ZnCl2 (aq) + H2 (g)
Then the iron can react with copper ions in a copper (II) nitrate solution. When the iron reacts with copper ions, copper metal forms on the surface of the iron.
Fe (s) + CuSO4 (aq) --> FeSO4 (aq) + Cu (s)
Fe (s) + Cu(NO)2 (aq) --> Fe(NO3)2 (aq) + Cu (s)
The zinc layer on the galvanized iron is silver colored, but the copper is orange. We can use this difference in color to create an interesting pattern or design.
Galvanized iron (Careful, edges may be sharp!)
Tin snips (to cut the galvanized iron)
Pencil with an eraser
Utility knife or Razor blades (BE CAREFULL!!!)
Paper clip (Hook)
25ml 0.05M Cu(NO3)2 (or CuSO4) solution in a beaker (one per table)
50ml 6M HCl, in a large beaker (one per table) – Caution: Corrosive
Where to find galvanized iron (or galvanized steal)?
The galvanized iron is often sold at hardware stores (Lowes, Home Depot, Carter lumber). Ask for metal flashing. Typically it is carried in the roofing department or near the area where they sell rain gutters and downspouts. Flashing comes in many materials, typically copper, aluminum, but you want the galvanized (or may be called galvanized iron or galvanized steal). They can also come in rolls or small sheets (5" x 7"). I personally believe the sheets are easier to handle and slice up. I cut my 5" x 7" sheets down into quarter pieces of 2.5" x 3.5".
Tin snips are necessary, if you want to slice the sheets up into smaller pieces, but ask around your school if anyone has a metal guillotine. If your school is lucky enough to have wood shop, metal shop, or Agriculture classes, they may have guillotine that can slice your flashing. My school has a foot operated (treadle) metal guillotine that makes slicing the ornaments much easier (http://www.bisonmachinery.co.uk/sheet_plate_working_machinery/guillotines/morgan_rushworth_asts_manual_treadle_guillotines.php ). Just watch your fingers.
1. Completely cover both sides of a piece of galvanized iron with masking tape. Mark where you want the hole (if any). This is the top of the ornament.
2. Draw design on the masking tape with a pencil. If you want, you may draw designs on both sides of galvanized iron.
NOTE: Bubble letters (letters that overlap or touch) do not work well. Letters, lines and spaces need to be about 1/8” or wider for good results
3. Use the utility knife (razor blades) to cut along the pencil marks and remove the masking tape so your designs are uncovered. (BE CAREFULL!!!)
4. Put on goggles and apron.
5. Using tongs, place the piece of galvanized iron in the baker of hydrochloric acid, HCl. Notice what happens. What gas is being produced?
6. Remove the piece from the acid as soon as the rapid formation of bubbles stops.
7. Rinse if off with water.
8. Dip the ornament into the copper (II) sulfate, CuSO4, solution or copper (II) nitrate, Cu(NO3)2, solution.
9. When the entire area of the design has been coated with copper, rinse it carefully with distilled water.
10. Optional: Dip the ornament into rubbing alcohol for a couple of minutes. Rubbing alcohol helps to loosen the glue of the tape.
11. Allow the copper to dry (the tape can still be wet).
12. CAREFULLY, remove the masking tape from the piece of iron. Do not touch the copper, it rubs off easily!
13. Attach the hook to the ornament.
14. Coat the piece with acrylic sealer. Holding the piece by the hook under a fume hood, spray both sides with sealer.
15. Hang your ornament in a safe place to dry overnight. You make take the ornament home the following day.
16. Take the ornament home and hang it on your “Chemis-tree”.