Density of Pennies - H Introduction Prior to 1982, pennies were made from pure copper. But as the cost of copper rose, it became more expensive to make a penny than the penny was worth. The solution to the problem was to make the penny from a less expensive metal, but maintain the look of a penny by adding a thin layer of copper on the outside of the new metal. In this lab you will examine pennies made before 1982 and those made after that time. You will collect data and determine the densities of the two types of pennies. From this information, you should be able to determine the metal found inside of the “new” pennies. Hypothesis Write a hypothesis stating what metal you think is found inside the penny. Include a brief explanation of why you chose this metal. Procedure 1. Make two data tables like the ones shown below. 2. Obtain two sets of 25 pennies. One set should all be Pre-1982 and the second set should all be Post-1982. 3. Using only one set of pennies, measure the mass of 5 pennies and record on your data table. Add 5 more pennies (10 total) and measure the mass and record. Repeat this process, adding 5 pennies each time, until the mass of all 25 pennies is determined. 4. Using the same set of pennies, measure the volume of 5 pennies by displacement and record on your data table. Repeat as in step 3 until all 25 pennies have been measured. 5. Repeat steps 3 and 4 using the other set of pennies. 6. Be sure to completely dry your pennies when finished. Pre-1982 Number of Pennies 5 10 15 20 25 Post-1982 Number of Pennies 5 10 15 20 25 Mass(g) Volume(ml) Mass(g) Volume(ml) Analysis 1. Do the pennies appear to have equal densities? 2. What does that tell you about the post-1982 pennies? 3. Make a graph of your data. You will have two lines on your graph. One for the pre-1982 and one for the post-1982 pennies. Place the mass on the Y-axis and the volume on the X-axis. Plot your points by using the mass and volume measurements as your points. Draw a best fit line through the points for each set of data. Color code your lines. 4. The density of each type of penny can be determined by calculating the slope of each line. Use the following formula to determine slope. Choose two points on your line to use in the formula. Slope= Y2 – Y1 X2 – X1 5. Use the provided list of element properties to choose 3 possible candidates for the metal found inside the post-1982 pennies. Conclusion Discuss the lab procedure and your results. Was your original choice one of the three determined in this lab? Error List three sources of error for this lab. Density of Pennies Lab Grading Rubric Name: _____________________ Block: ______________ Component Title 5 points Purpose 5 points Hypothesis 5 points Procedure 10 points Data 10 points Analysis 20 points Error Analysis 5 points Conclusion 5 points Participation 10 points Total Points 75 Clearly reflects lab 5 points Clearly stated 5 points Present-with reasons 5 points Detailed, all points present, step by step 10 points Present, complete, neatly done 5 points Present, all questions answered, graph present 20 points 3 sources of error identified 5 points Well written paragraph, refers to data/procedure 5 points Worked consistently, safety gear 10 points Due Date:_________ Possible Points Present, but unclear 1-4 points Present, but unclear 1-4 Points Present but incomplete 1-4 points Present, but incomplete or not clear 1-9 points Present, but needs work Points Absent 0 points Absent 0 points Absent 0 points Absent 0 points Absent 0 points 1-9 points Present, but incomplete Absent 0 Points 1-20 points 1-2 sources identified Absent 1-4 points Present, but does not refer to data/procedure 0 points Absent 1-4 points Had to be reminded to focus 2-3 times 7-8 points 0 points No work Had to e reminded to focus 45 times 4-6 points 0 points