Pennium

Intro-  Most elements consist of two or more naturally occurring isotopes.  (Atoms of an element that vary because they have different mass numbers, numbers of neutrons) Different isotopes of an element have different relative atomic masses due to the different numbers of neutrons in the nucleus. 
in this lab you are pretending that you have an element called Pennium, you will be given a bag of this element.  THrough comparing the masses of the "penny atoms" you will see how many different Pennium isotopes are in the bag.  You will then determine the average atomic mass of Pennium using the following equation:  (average mass of isotope 1)(percent abundance of isotope 1)+(average mass of isotope 2)(percent abundance of isotope 2). Next you will choose another element (Fivecentium) to be the accepted mass standard to which all other atoms are compared for mass.  You'll use the mass of a nickel to determine the relative mass of Pennium, Dimeium, and Quarterium.   All relative masses will be expressed in CMU (Coin Mass Units).


Objectives-  In this lab you will investigate the concept of atomic mass and how it was derived.  You will develop your own unit of measure, the CMU, and use it to measure the relative masses of other coins.  At the conclusion of this lab you will be able to explain how scientists developed the system for AMU's (atomic mass units) and how it is applied to determine the relative masses of other atoms of other elements. 


Procedures-  
Part I
     1.  Obtain a packet of pennies.
     2.  Sort the pennies into two groups: pre 1982 and 1982 and newer. 
     3.  Measure the mass (in grams) of each stack of pennies, record the mass (in grams) of each penny stack in a data table.  Count the number of pennies in each stack.  
     4.  Measure the mass (in grams) of a quarter, nickel, and dime.  Record these values in a data table. 
     5.  Answer the questions below and then continue with Part II. 


                                                                           Pennies
                                               Pre (9)                                           Post (8)
Mass (group)                     27.9 grams                                       10.98 grams


Average mass (one)           2.9 grams                                          2.5 grams


to be cont... 


Part I Questions
1.  Does each penny have the same mass?  A:  sure did
2.  Can you identify two penny isotopes based on masses of the pennies? Explain.  A:  Not unless you knew which time period (post or pre) had the heavier pennies. 
3.  What does your data tell you about the relationship between mass of a penny and date of a penny.  Make a generalization.   A: the newer they pennies are, the less the mass is.  


Procedures
Part II
1. Determine the average mass of pre- 1982 pennies.  (Record average)
2. Determine the average mass of post- 1982 pennies.  (Record average)
3. Determine the percentage of your pennies that are pre- 1982 and the percentage that is post- 1982.  These percents should add up to 100%.  What you have calculated is the percent abundance of each group of pennies (penny isotope).
4. Choose one of your coins to make a CMU (coin mass unit).  The mass of a nickel (Fivecentium) is one CMU.  Use the mass of a nickel to calculate the mass of a quarter (Quarterium), dime (Dimium), pre-82 (Pre-82 Pennium), post-82 pennies (Post-82 Pennium).  Show all calculations, and record all data in a data table. 
5. Determine the average mass of Pennium in CMU's using the percent abundance (from #3) of each pennium isotope (pre-82 and post-82) and the mass of each pennium isotope in CMU's (from #4).  


Questions and Conclusions
Part II
1. Make a statement about the average penny mass of pre-82, post-82, and pennies in the packet. 
2. Explain how you derived the unit "CMU".
3. Using the idea you explained in #2 above, how did scientists obtain the Atomic Mass Unit (AMU) to measure the mass of atoms of different elements?
4. What is your weight in CMU's?  (Remember 1lb= 2.205 Kg)
5. Write a statement that compares what you did in this lab o what scientists have done to find the average atomic masses of the elements.