# How does the Mass of a Penny Depend on the Year it was Minted_1_

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How much does a penny weigh?

Do all pennies weigh the same?

You can find out by measuring the mass of pennies
from 1960 through 2003.

Make a prediction
Do all pennies weigh the same? If you made a graph of the mass of a penny
for 1960 through 2003, what would this graph look like if pennies always
weighed the same?

Could pennies collect dirt as they get older? What would your graph look
like if the pennies get heavier the older they get?

Could pennies wear off as they get older? What would your graph look like if
pennies get lighter the older they get?

Are there any other ways that you can think of that might make the mass of
pennies change?

How much
the penny
weighs

An extension for first graders (and review for
Dates –A Lesson for First and Second Graders

Am I older or younger than my penny?

ring_00_nl_1_p.html

Look at a penny. Where does it show the
date? What other information is on the
front of the penny?

Who’s picture is on the front of a penny?

you tell?
Teacher Notes:

Small Change
3.2

3.0
penny in grams (g)
Mass of each

2.8

2.6

2.4

2.2

2.0
1960   1965   1970   1975     1980   1985     1990      1995     2000
Year minted

We plotted the mass of pennies in grams and the years in
which they were minted. We discovered that the mass was the
same up until 1983. After 1982, pennies were lighter than they
were before.

I did some additional research about the change in composition of pennies minted after 1982
and used that information to write an example caption of my own.

For 1960 through 1982, the average mass of a penny is about 3.1 grams. However, for
pennies minted between 1983 through 2001, the average mass is only about 2.5 grams.
Before 1983, pennies were made of copper with only about 5% zinc. In 1982, the
composition changed. Since 1982, the composition of pennies has been 97.5% zinc and only
2.5% copper. Each penny has a zinc core and a thin copper skin. The newer pennies look
similar on the outside in size and color to the pennies made before 1983. But, the density
of zinc is less than copper. Thus, the average mass of a penny made primarily of zinc is less
than the average mass of a copper penny.
Reference: “Penny Skins” from the Carolina Biological Supply Chemistry web site:
http://www.carolina.com/chemistry/experiments/pennyskins.htm

This reference describes a similar lab activity for middle school students.

Template for making a penny plot:

I printed this in color on peel off labels. Students cut out individual pennies and used these
as data points on a paper chart in the front of the room.

3.1
grams

2.5
grams

1980     1981     1982      1983      1984      1985     1986
Plotting with Excel
the mass of each penny and create their charts using the Chart Wizard.
Why are the pennies different?

The teacher can cut pennies in half with tin
shears. Look inside. What is different
between the pennies made before 1983 and

I used chocolate covered cookies or candy
with an outside and inside layer to illustrate
this concept.

Inquiry skills:
□ Observing
□ Classifying and sequencing
□ Communicating
□ Measuring
□ Predicting
□ Hypothesizing
□ Inferring
□ Defining, controlling, and manipulating
variables in experimentation
□ Designing, constructing, and interpreting
models
□ Interpreting, analyzing, and evaluating data.

Scientific Investigation, Reasoning, and Logic
2.1 The student will plan and conduct
investigations in which
□ Observations are repeated to improve
accuracy;
□ Two or more attributes are used to classify
items;
□ Pictures and bar graphs are constructed using
numbered axes;
□ Linear, volume, mass, and temperature
(centimeters, meters, liters, degrees Celsius,
grams, and kilograms) and standard English
units (inches, feet, yards, pints, quarts,
gallons, degrees Fahrenheit, ounces, pounds);
□ Observation is differentiated from personal
interpretation, and conclusions are drawn
based on observations;
□ Simple physical models are constructed;
□ Conditions that influence a change are
defined; and
□ Unexpected or unusual quantitative data are
recognized.

increasing emphasis on conducting investigations.
Students are expected to be able to develop
questions, formulate simple hypotheses, make
predictions, gather data, and use the metric
system with greater precision. Using information
to make inferences and draw conclusions becomes
more important.
Ideas for assessment:

What do students need to know about
measurement?

What do students need to know about making
predictions?

What do students need to know about graphing?

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