Title: Penny Mass

Title: Penny Mass

Description: Students mass pennies to practice using the balance and see how the mass of pennies has changed over the years.

Materials: a variety of pennies, especially some with dates in the 60’s and 70’s. a balance, graphing calculator (optional)

Prior knowledge: Students need to know how to use a balance. For teachers you may want to know that pennies vary in mass from 1.5 g to about 3 g. The mass of old pennies is greater than newer ones. In the mid 80’s zinc centers were placed in pennies and students will see the mass drop about that time. Do not share this information with students before the activity, allow them to try and figure it out.

Time Needed: one 50 minute class period

Procedures:

1. You may wish to have students bring pennies from home to mass. Encourage them to bring old ones but not valuable ones.

2. Each group of students needs 20 pennies, you may wish to count them out in advance and put them in paper cups.

3. Students may need help scaling their graphs and understanding a line of best fit. Graphing calculators will do this for students if you choose to use them.

Scoring Guide

1. Students collect and graph data………………15 pts

2. Students correctly answer analysis questions…5 pts

Answers:

1. Pennies drop in mass.

2. They change because their composition changed,

3. You could not do this on your bathroom scale because it does not measure in small enough increments.

4. They wear out or get dirty.

5. The mass of pennies is affected by the precision of the balance and by how they have been handled.

Title: Penny Mass

purpose: To practice using the balance and see if the date pennies were made affects their mass.

materials: 20 pennies, balance

procedure:

1. Record the mass and date of each penny.

2. Graph your results. Draw a line of best fit to describe the dots.

prediction: Will the mass of pennies change from year to year? How?

data:

Analysis:

1. How does the mass of pennies seem to change as time goes by?

2. Why might this have occurred?

3. Could you have done this lab on your bathroom scale? Why?

4. What might affect the mass of pennies besides when they were made?

5. Why might two pennies of the same date have a different mass?

Conclusion: 2 things you learned.