Monday, 9/6 - Labor Day - No School
Tuesday, 9/7
- All students need a Lab Book in order to begin the lab on Wednesday
- Lab Write Up Review
- Book Handout - Students need to bring ID cards to Class Today
Wednesday, 9/8 - Late Arrival
- Measurement and Penny Lab Begin - Students must have PreLab completed
Thursday, 9/9
- Measurement and Penny Lab Continues
Friday, 9/10
- Lab Work must be completed
- Safety Test
Lab Write Up Procedures
Title: Pennies Lab
Purpose: Sometime between 1977 and 1987 the U.S. Mint made a change in the composition of pennies. The purpose of this lab is to determine what year the new pennies started to be produced. This will be done based on density calculations.
Materials:
1. One set of 10 pennies for each year in the late 1970’s-1980’s
2. A 50 ml graduated cylinder
3. An electronic balance
Safety: None to be noted for this lab
Procedure:
1. Obtain 10 pennies for each year in the 1970, 1980, and 1990
2. Determine the mass of each “decade” of pennies using an electronic balance.
3. Record the mass of each penny
4. Obtain a 50 ml graduate cylinder
5. Place water in the graduate cylinder
6. Record the initial volume of water in the graduate cylinder
7. Place two or three pennies in the graduate cylinder.
8. Record the number of pennies used
9. Record the final volume of the water in the cylinder.
10. The difference between the initial volume and the final volume of the water is the volume of the pennies.
11. Calculate the volume of each penny by dividing the difference between the initial and final water volume by the number of pennies placed in the graduate cylinder.
12. Record the volume of the pennies. (Assume the volumes are uniform for all pennies in each decade)
13. Repeat steps 2 – 12 for each “decade” of pennies
14. Calculate densities for each penny used
15. Record the density of each penny
Data: (Example)
1970
Number of Pennies ______________________
Initial Vol______________________________ ml
Final Vol______________________________ ml
1980
Number of Pennies______________________
Initial Vol______________________________ ml
Final Vol______________________________ ml
1990
Number of Pennies______________________
Initial Vol______________________________ ml
Final Vol______________________________ ml
Calculations:
1970
Volume Difference_______________________ ml
Density = mass/volume
(Show calculation for at least one for each decade)
1980
Volume Difference_______________________ ml
Density = mass/volume
1990
Volume Difference_______________________ ml
Density = mass/volume
Conclusion:
The purpose of this lab was to determine when the US Mint made a change in the composition of the pennies made in the United States. This was done based on the calculation of density. It was determined that the US Mint changed the penny in 1982. It was a sudden change. Prior to 1982 the densities of the pennies ranged from 8.8 to 9.1 grams/ml. In 1982 and after the density of pennies ranged from 7.5 to 7.9 grams/ml.The density clearly changed in 1982. It decreased. The volume of the penny did not seem to change. The mass of the penny did significantly change. As a result, it could best be hypothesized that the material which makes up each penny changed. Prior to 1982 pennies were made of copper. In 1982 Zinc was added to the composition of each penny therefore reducing the mass of penny.
The primary source of error in this lab was the measure of volume. I used a 50ml graduate cylinder. The markings were very inaccurate and it was difficult to determine the exact amount of change for the pennies used. If I had to change this lab, I would find a way to more accurately measure the volume of each penny.
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