This document provides instructions for making a hollow penny through a chemical reaction. It explains that filing or cutting a post-1982 penny exposes the zinc interior, which then reacts with hydrochloric acid while the outer copper layer remains intact. Specifically, it outlines: 1) Scoring the edge of pennies with a file or sandpaper to expose the zinc interior. 2) Placing the pennies in hydrochloric acid for 6 hours, during which the zinc dissolves, leaving a hollow copper shell. 3) Rinsing the pennies and adding baking soda to neutralize residual acid, resulting in fragile hollow copper pennies.

2. The Hollow penny

3. The Hollow penny
Copper doesn't react with hydrochloric acid (HCl), while
zinc metal does. A hollow penny can be made by taking a
file and nicking the edge, exposing the zinc metal core, and
then placing the penny in HCl solution. The zinc core will
eventually dissolve in the acid, leaving the thin layer of
copper and a "hollow penny

4. The Hollow penny

5. What do I do?
1. Pour a little muriatic acid over the pennies so that they are
covered. Bubbles will start to form immediately. Set the
container somewhere where it will be safe from spills, children,
and pets. Let the reaction proceed for about 6 hours.
2. Carefully pour off the muriatic acid. You can wash it down a
drain, providing you use a lot of water.
3. Fill the container with water. Add a little baking soda to
neutralize the residual acid.
4. Examine your penny. The hollow penny will be a fragile copper
foil.

6. Let do it again, slowly!!!
This is an easy chemistry project that uses common
materials.
You take a post-1982 penny, score the copper surface expose
the zinc interior, react the zinc with acid, and are left with a
hollow copper penny.

7. Here’s How!!!
Statistics for this demo!
Difficulty: Average
Time Required: 6 hours
Here's How:

8. First
1. You need to expose the interior of the pennies.
You can score the edge of the pennies with a file or
snip them with wire cutters, but I think the easiest
way to expose the zinc is to rub the edge of each
penny along a brick or concrete block. You could
use sandpaper, if it's available. Use whatever is
Handy.

9. First
To expose some of the zinc (don't go all the way around the
coin). If you can see silver metal under the copper of the
penny, you're ready to proceed to the next step.

10. Secondly
2. It's best to do this step outdoors or under a fume hood,
wearing gloves and protective eyewear. Read the safety
precautions on the muriatic acid container. Basically, this is
hydrochloric acid. Treat it with respect. Place the pennies
in your container.

11. Muriatic Acid
Pour a little muriatic acid over the pennies
so that they are covered. Bubbles will start to form
immediately. Set the container somewhere where it
will be safe from spills, children, and pets.
Let the reaction proceed for 6 hours

12. The reactions taken place are:
Zn(s) + 2HCl(aq)  ZnCl2(s) +H2(g)
Proceeds to completion
Cu(s) + 2HCl(aq) 
No reaction occurs! With low conc. HCl