How To Make Hollow Pennies
A PARENT SHOULD SUPERVISE THIS ACTIVITY!
Materials:
post-1982 US pennies


muriatic acid (from a hardware store)

a disposable plastic container or glass jar

baking soda

water
Procedure:
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 maybe the easiest way to expose the inside
of the penny is to rub the edge of each penny along a brick or concrete block. Once you
can see silver metal under the copper of the penny, you're ready to proceed to the next
step.
2. Do this next step outdoors. You should also wear kitchen gloves and protective eyewear.
Read the safety precautions on the muriatic acid container. Basically, it is hydrochloric acid
and needs to be treated with respect. Place the pennies in your container. 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.
3. Carefully pour off the muriatic acid. You can wash it down a drain, providing you use a lot
of water.
4. Fill the container with water. Add a little baking soda to neutralize the residual acid.
5. Examine your penny. The hollow penny will be a fragile copper foil.
Conclusion:
1. Attach a picture of your pennies.
2. Go on line and describe what changed with pennies in 1982.
3. Describe (chemically) what happened to the metal on the inside of the penny (again, a
little on line research may be in order here.)