Isotopes
of Pennies PreLab
You will do a lab that
will deal with isotopes, mass number, and atomic mass. Before you begin your
work in the lab, try to explain these terms in your own words. After you have
finished the lab, you will have a chance to revise your explanations based on
what you have learned in the activity.
Isotope:
Mass
number:
Atomic
mass:
Average
Atomic Mass:
In 1982, the
Isotopes
of Pennies LabLab
Part
A (note:
answers should only be as accurate as your instrument.
Remember, “significant digits!!!”)
1.
Obtain a sample of ten pennies.
2.
Mass several pre1982 (old)
pennies and record their average mass.
______g
show
work here:
3.
Mass several post1982 (new)
pennies and record their average mass _____g
show
work here:
4.
Calculate the mass of three old
pennies plus seven new pennies.
show
work here:
______g
5.
Find the average mass for the last answer.
show
work here
______g
6.
Now mass your sample of three old and seven new pennies. Record the mass.
______g
7.
Find the average mass of a penny in your sample.
show
work here
______g
8.
Compare your answer for number five to your answer for number seven. Is your
average mass closer to the mass of an old penny or a new penny? Why?
9.
How is this average mass related to atomic mass?
Part
B
1.
Obtain a sample containing six old pennies and four new pennies.
2.
Using the mass of an old penny and a new penny from part A above, calculate the
average mass for this sample of pennies.
show
work here
______g
3.
Now mass your sample of pennies. Record the mass.
______g
4.
Divide the mass of your sample of ten pennies by ten to find the actual average
mass of a penny in this sample.
show
work here
______g
5.
Compare your answer from number two to your answer for number four. Is the
average mass closer to the mass of an old penny or a new penny? Why does
this happen? Is it a similar reason
as in part A?
Part
C: The Mystery Sample
1.
Return your sample of ten pennies
from part B to your teacher. Get a canister of pennies.
Don’t open it.
Write its identifying
letter here:_____
2.
Record the mass of the empty film canister, which is on the canister.
______g
3.
Mass the sealed film canister containing ten mixed pennies.
______g
4.
Return the canister.
5.
The chart on the next page needs to be filled out by you so that you can
use it to figure out what your mystery sample contained.
Calculations:
#
of New Pennies 
#
of Old Pennies 
Total
Mass (g) 
Average
Penny Mass (g) 
0 
10 


1 
9 


2 
8 


3 
7 


4 
6 


5 
5 


6 
4 


7 
3 


8 
2 


9 
1 


10 
0 


How
many old pennies did your container have? ______
How
many new pennies did your container have? ______
What
percentage of old and new pennies do you have?