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 United States government changed the way it minted pennies. Before 1982, pennies were made of 95% copper and 5% tin. Now they are made of zinc coated with copper. Because they weigh different amounts (have different masses), we can call them isotopes of pennies.

 

  1. What do the two kinds of pennies represent in this exercise?

 

 

 

 

  1. How do the pennies differ? How do isotopes differ?

 

 

 

 

  1. What do the pennies have in common? What do isotopes have in common?

 

 


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 pre-1982 (old) pennies and record their average mass.   ______g

show work here:

 

 

 

3. Mass several post-1982 (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?