Isotopes and Average Mass Activity
Your Lab Report should include your partner’s name, date, title, purpose, data table and
answers to questions.
1. In this activity, we will use paperclips to simulate atoms of the same element. Today
we will look at one element: Paperclipium.
2. Select at least 10 paperclips of the same size and measure their total mass. Record all
data on the lab data sheet you create.
3. Determine the AVERAGE MASS of ONE paper clip of that size. Record data.
4. Repeat steps 1-2 for all three sizes of paperclips. Record data.
5. Now, make a MIXTURE of at least 20 paperclips of all three sizes. Do not use equal
numbers of the different types. Record the number of each type of paperclip you used
to make up the mixture (for example: 7 small + 9 medium + 8 large = 24 total).
6. Determine the percent of the total that each variety of paperclip contributes to the
mixture. Show all calculations. Record.
7. Measure the total mass of the paperclip mixture. Record data.
8. Determine the AVERAGE MASS of ONE paperclip of the MIXTURE. Show Work
10. Calculate the weighted average mass of the paperclip mixture using the average masses of
each type of paperclip calculated in steps 1-4 and the percent of each variety used that
you determined in step 6..
11.Compare this weighted average (calculated) with the average you obtained in steps 7-8.
What is the percent error between these two figures? %error = /true-calculated/
Record your results. true
Answer the following questions in your lab report using complete sentences:
a. What is an isotope?
b. What is a weighted average?
c. Why are average atomic masses not whole numbers?
d. Why don't the atomic mass numbers match, even when we take the very small
mass of electrons into account?
e. What was the average mass of a "Paperclipium" atom? Did any paperclips have
this mass? Explain.
f. How are the three isotopes of hydrogen (protium, deuterium, and tritium) alike?
How are they different?
g. Copper has two isotopes, copper-63 and copper-65. The relative abundance of
copper-63 is 69.1% and copper-65 is 30.9%. Calculate the average atomic mass