THE HOLLOW PENNY LAB - MAKEUP
Name___________________ Period______
Lab Station ______
Introduction - Pennies
Penny’s are made of copper….aren’t they? The outside is certainly made of copper, but that’s not the whole story.
In this lab, the composition of two pennies from two different years will be investigated.
Before 1982 a penny was made almost entirely out of Cu (copper metal). However, during 1982
the value of copper increased so much that the amount of Cu in a penny was worth more than
the penny itself. Some people were actually collecting huge amounts of pennies and melting them
down to sell bulk Cu. Also, the government was loosing money by minting new pennies.
Therefore, the Mint decided to change the composition of the penny sometime during the middle
of 1982. Since Zn (zinc metal) was less expensive than Cu, the mint decided to make the penny
out of Zn, and then just cover the outside with Cu. Thus the penny looked the same as before,
but was mostly made out of Zn, thus making it less expensive to make.
In today’s lab you will develop a procedure to determine what is on the inside of two pennies from two different
years. You will be using a strong acid, HCl (hydrochloric acid), which reacts with zinc metal, and not with copper.
When HCl reacts with Zn a single replacement reaction takes place. The reaction is shown below.
Zn (s) + 2HCl(aq) → ZnCl2 (aq) + H2 (g)
Background – Chemical Reactions
Oxidation-reduction, or redox, reactions are reactions in which electrons are transferred from one element to
another. A common type of redox reaction is a single replacement reaction. Single replacement reactions involve
the replacement of one element in a compound with another element. The general form for single replacement
reactions is shown in the equation #1 below:
A + BC → B + AC
Metals are commonly involved in single replacement reactions. Some metals can replace other metals in their
compounds, while some metals cannot. In equation #1, if “A” and “B” are metals, “A” replaces “B” in it
compound “BC”. The reaction is not reversible, so “B” cannot replace “A” in the compound “AC”. The ability to
replace another metal determines a metal’s reactivity – the better the ability to replace another metal, the more
reactive a metal is. The activity series of metals is a scheme that places the metals in order of reactivity (see Table
1). The metals at the top are the most reactive and can therefore replace most other metals. A metal can replace
another metal if is appears above that metal in the activity series. In equation 1, “A” must be the more reactive
metal (higher up on the activity series and capable of replacing “B”), while “B” is the less active metal (lower on the
activity series and not capable of replacing “A”). For the purpose of this activity Hydrogen is considered a metal.
Table 1: Activity Series of Metals
Name of Metal
Lithium
Potassium
Calcium
Sodium
Magnesium
Aluminum
Zinc
Iron
Lead
(Hydrogen)
Copper
Mercury
Silver
Gold
Most Reactive
Least Reactive
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Looking at a specific example, if the two metals are aluminum, Al, and copper, Cu, then in equation 1 “A” must be
aluminum and “B” must be copper since aluminum appears higher up on the activity series than copper and is
therefore a more active metal than copper. An example of a reaction involving these two metals is the reaction
between aluminum metal and cupric chloride solution (see equation #2 below):
2Al (s) + 3CuCl2(aq) → 3Cu(s) + 2AlCl3 (aq)
In this reaction, aluminum is said to replace copper since the cupric chloride compound becomes aluminum
chloride. The redox terms, the cupric ion has been reduced to copper metal, while aluminum metal has been
oxidized to the aluminum ion. Because copper appears below aluminum on the activity series, it is less reactive than
aluminum and cannot replace aluminum in a compound. As a result, the reverse of equation #2 does not occur
spontaneously (see equation #3).
Cu(s) + AlCl3(aq) → NR (no reaction)
Introduction/Background Questions:
1. Why were copper pennies filled with another metal instead of being made of pure copper?
2. In order to determine the contents of two different pennies, what strong acid will be used?
Why?
The following reaction will be observed during this lab.
Zn (s) + 2HCl(aq) → ZnCl2 (aq) + H2 (g)
3. Write the word equation for the chemical reaction above.
4. What type of reaction is the chemical reaction above?
5. Write the general form (using letters A, B & C) for the type of reaction above:
6. What is a redox reaction?
7. Could Iron replace Hydrogen in the following reaction? (hint: see activity series)
Fe(s) + HCl (aq)
 H2 (g) +
FeCl2 (aq)
Why?
Hypothesis:
1. Evidence of Reaction
What evidence can you expect to see that the reaction is taking place?
Pre-1982 Penny
Post-1982 Penny
2. Mass of Pennies after Reaction
Which penny (pre-1982 or post-1982) do you expect to have the greater mass loss due to the reaction?
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Materials:
Balance
Beaker, 150-mL
Beaker, 250-mL
Graduated cylinder, 50-mL
Hydrochloric acid solution, 6M, HCl, 40mL
Paper Towels
Post – 1982 penny
Pre – 1982 penny
Tongs
Triangular file
Water, 125 mL
Safety Precautions:
Hydrochloric acid solutions is corrosive to skin and eyes and is moderately toxic by ingestion and
inhalation. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron.
Procedure:
DAY 1:
1. Using a triangular file, file three notches in a pre-1982 and a post-1983
penny. See Figure 1.
2. Weigh the notched pre-1982 penny on a balance. Record its weight in the
Data Table.
3. Weigh the notched post-1982 penny on a balance. Records its weight in the
Data Table.
4. Caution: 6 M hydrochloric acid solution is corrosive to skin and eyes. Avoid
all contact with skin and eyes. Pour about 40 mL of 6 M hydrochloric acid
solution into a 150-mL beaker.
5. Using tongs, place both pennies in the beaker of hydrochloric acid solution so that they are both
completely submerged.
6. Observe the reaction between the hydrochloric acid solution and the pennies. Record your
observations in the Observation Table.
7. Set the beaker in a safe place as instructed by your teacher and allow the reaction to continue
overnight.
8. Clean up your lab station.
DAY 2:
1. Fill a 250-mL beaker about half-full with water.
2. Using tongs, transfer both pennies from the hydrochloric acid solution to the beaker of water.
Still using tongs, move the pennies through the water to rinse them.
3. Remove each penny form the water and hold each under running water to thoroughly rinse it.
4. Look into the center of each penny through one of the notches. Record your observations in the
Observation Table.
5. Dry each penny with a paper towel. Write your name on a clean paper towel. Place the pennies
next to your name. Allow them to dry completely overnight.
6. Clean up your lab station.
DAY 3:
1. Weight each completely dry penny on a balance. Record the weight of each penny in the Data
Table.
2. Clean up your lab station.
3. Answer the analysis and conclusion questions.
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OBSERVATIONS TABLE:
Day 1
Observations of the Reaction between Hydrochloric Acid
and the Pre-1982 (older) Penny
Nothing happened
Day 1
Observations of the Reaction between Hydrochloric Acid
and the Post-1982 (younger) Penny
When placed in the
hydrochloric acid bubbles
started forming immediately
Day 2
Observations of Pre-1982 (older) Penny after being
submerged in the HCl solution overnight
Day 2
Observations of Post-1982 (younger) Penny after being
submerged in the HCl solution overnight
It remained the same
It became hollow and flimsy
DATA TABLE: PRE – 1982 (OLDER) PENNY
Mass of Penny Before Experiment (g)
3.07 g
Mass of DRY Penny after Experiment
3.06 g
Calculate Mass lost (if any)
% weight of Copper in Penny
(mass at end of experiment ÷ mass at beginning) x 100
% weight of other Metals in the Penny
100% - (% Copper from above)
DATA TABLE: POST – 1982 (YOUNGER) PENNY
Mass of Penny Before Experiment (g)
2.45 g
Mass of DRY Penny after Experiment
0.06 g
Calculate Mass lost (if any)
% weight of Copper in Penny
(mass at end of experiment ÷ mass at beginning) x 100
% weight of other Metals in the Penny
100% - (% Copper from above)
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Data Analysis Questions:
1. Which metal, copper or zinc, reacts with the hydrochloric acid?
2. How do you know? (support your answer to #1 by using data from the lab)
3. Most acids, even strong ones like hydrochloric acid, usually have no immediate effect on copper. However,
copper with react vigorously with nitric acid. Is it possible then to substitute nitric acid for hydrochloric
acid in this lab?
Why?
4. What is the name of the element in the gas bubbles? Oxygen, Hydrogen, or Chlorine?
5. Did each penny lose approximately the same mass in the reaction or did they lose different amounts?
6. Look at the Activity Series in Table 1, should copper react with the Hydrogen in HCl? (Hint: should
copper metal be able to replace hydrogen ions?) Explain your answer (how did you know?).
7. Based on what happened in the lab, look at the Activity Series chart and propose a metal that could have
been used to fill the post 1982 penny (there is more than one possible right answer).
8. Write the chemical equation for the reaction between Copper metal and Hydrochloric Acid. If no reaction
occurs, write “NO REACTION” on the products side. (show your work)
9. Write the chemical equation for the reaction between the metal you chose in #7 and Hydrochloric Acid.
(show your work…don’t forget to write the appropriate chemical formulas and balance the equation)
10. If cost were not a factor, what would be the best metal out of which to make coins? (Hint: look at the
Activity Series chart and think about durability).
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Conclusion:
1. Summarize what you did in the lab (materials used procedures)
2. What was the main point of the lab?
3. Evidence of Reaction – Was your hypothesis correct? Did you see the evidence that you expected to see in
the pre-1982 and post 1982 pennies? Comment on the observations seen in the lab!
4. Mass of Pennies after the Reaction – Was your hypothesis correct? Did you choose the correct penny
(pre-1982 or post-1982) that would have the greater mass loss due to the reaction? Use data from the lab!
5. Discuss your overall confidence in lab – what did you do well and what could you have improved?
FYI: Economics and chemistry are related. Did you know that sulfuric acid can be considered a barometer of the
business world? A country’s economy is closely related to its sulfuric acid consumption. (World production of
sulfuric acid in 2001 was 165 million tons, with an approximate value of US $8 billion.) Principal uses include ore
processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis. So, study your
chemistry and your economics. Both can be important to your own economic well-being.
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