Download Isotopes of Pennies and more Study notes Finance in PDF only on Docsity! Isotopes of Pennies Name ___________________________Date ______________ Period _______ Pre-Lab Questions You will do a lab that will deal with isotopes, mass number, and atomic mass. Before you begin your work in the lab, try to explain these terms in your own words. After you have finished the lab, you will have a chance to revise your explanations based on what you have learned in the activity. Terms: Isotope: Atomic Number: Mass Number: In 1982, the United States government changed the way it minted pennies. Before 1982, pennies were made of 95% copper and 5% tin. Now they are made of zinc coated with copper. Because they weigh different amounts (have different masses), we can call them isotopes of pennies. 1. What do the two kinds of pennies represent in this exercise? 2. How do the pennies differ? How do isotopes differ? 3. What do the pennies have in common? What do isotopes have in common? Part A 1. Obtain a sample of 14 pennies. 2. Weigh 5 pre-1982 (old) pennies and record their total mass. ______g. Then, divide your total by 5 to determine an average mass. Record _________g. 3. Weigh 5 post-1982 (new) pennies and record their average mass. ______g. Then, divide your total by 5 to determine an average mass. Record _________g 4. Calculate how much three old pennies plus seven new pennies should weigh. Record the predicted total mass ______g 5. Divide your answer for number 4 by 10 to find the weighted average mass of the pennies in the sample containing three old plus seven new pennies. ______g 6. Now, weigh your sample of three old and seven new pennies. Record the total mass of your sample ______g 7. Divide your answer for number six by ten to find the average mass of a penny in your sample ______g ☺ Compare your answer for number five to your answer for number seven. Is the weighted average mass closer to the mass of an old penny or a new penny? Why? ☺ How is this weighted average mass of the pennies related to atomic mass (of atoms)?
