Density of Pennies

**Questions:**

Are the densities of pennies made before and after 1982 different? What does density tell you about the composition of pennies?

**Materials:**

20 pennies made before 1982

20 pennies made after 1982

triple-beam balance

50-mL graduated cylinder

**Procedure:**

Using the balance, determine the mass of 20 pennies minted before 1982. Record your mass on the data table provided. Repeat your measurement two more times with 20 different pennies each time. Average the results of the three trials to obtain the average mass of 20 pennies minted before 1982.

Follow the same procedure for the pennies minted after 1982.

Pour exactly 30 mL of water into a 50-mL graduated cylinder. Add 20 pennies minted before 1982 to the graduated cylinder. (

Be careful not to splash water to the sides of the graduated cylinder) Recored the volume of the water on the data table. Repeat this procedure two more times with 20 different pennies. (Make sure the pennies are completely dry) Average the results of the three trials to obtain the average volume of the pennies.Follow the same procedure as in #3 with the pennies minted after 1982.

Using the average volume and the average mass of the two sets of pennies, determine the average density of each set and record on the data table.

Review your data for any large differences in trials.

Compare the average experimental densities of the two sets of pennies with the known densities of metals.

**Discussion:**

Why does the procedure include three trials instead of one trial for each set of pennies?

How would you recognize an inaccurate or incorrect set of data?

What might be some possible causes for such faulty data?

What would a scientist do with sets of data that appeared to be inaccurate or incorrect? Why?

Data Table

Post 1982

Trial 1 Trial 2 Trial 3 Mass of 20 pennies Initial volume of water Final volume of water Volume of 20 pennies Average mass of 20 pennies Average volume of 20 pennies Average density of 20 pennies

Calculations:

Pre 1982

Trial 1 Trial 2 Trial 3 Mass of 20 pennies Initial volume of water Final volume of water Volume of 20 pennies Average mass of 20 pennies Average volume of 20 pennies Average density of 20 pennies

Calculations: