The dry lab requires you to think about how you would perform the experiment if you were actually in a laboratory. Read through the materials list and all of the directions. You'll be given the data necessary to complete the lab, as if you had gathered them yourself. You should then complete the lab report as you normally would. Your materials are listed below.

Nuclear Physics Materials: Small plastic or cardboard box with lid 200 pennies Computer with graphing software 50 thumbtacks (with flat, domed heads) Materials for Exploring Further: Kit of radioactive rocks Geiger counter (radiation monitor) Gas discharge tubes with power supply (H, He, Ne, Ar) Handheld visual spectroscope Periodic table In this lab, you will investigate the meaning of half-life and learn how it is used to measure the decay of unstable atoms. Procedure Experiment 1: Radioactive Decay of Pennies 1. In this experiment, pennies that are placed heads-up will represent unstable, radioactive atoms (atoms that have not yet decayed). Pennies that are placed tails-up will represent stable atoms (atoms that have already decayed). . Place 200 pennies heads-up in the bottom of the plastic box. Record the number of pennies in the box that are unstable (heads-up) and the number that are stable (tails-up) in data table 1, in the row for 0 half-lives passed. . Place the top on the box and shake the box vigorously for a few seconds. Remove the top. Count and remove all pennies that are now stable (tails-up). Record the number of unstable (heads-up) and stable (tails-up) pennies in data table 1, in the row for 7 half-life passed. Remove all stable (tails-up) pennies from the box and set them aside. . Repeat step 3 nine more times, counting and removing all pennies that become stable (tails-up) each time. Record your data in data table 1. . Use a computer to graph the data. Follow instructions in the graphing software package or from your teacher in order to make the graphs. Plot the number of half-lives on the x-axis and the number of unstable (heads-up) pennies on the yraxis. Experiment 2: Radioactive Decay of Thumbtacks 1. For this experiment, thumbtacks with their points sticking straight up will represent unstable atoms (atoms that have not yet decayed). Thumbtacks with points touching the table will represent stable atoms (atoms that have already decayed). 2. Place 50 thumbtacks with points sticking straight up in the bottom of the plastic or cardboard box. Record the number of thumbtacks in the box that are unstable (pointing up) and stable (pointing down) in data table 2, in the row for 0 shakes. 3. Place the top on the box and shake the box vigorously for a few seconds. SAFETY NOTE: Ensure the top is fastened securely before you begin shaking! Remove the top. Count and remove all thumbtacks that are now stable (pointing down). SAFETY NOTE: Handle thumbtacks with caution, and place "decayed" thumbtacks away from your working surface and away from the working space of any classmates. Record the number of thumbtacks that are unstable (pointing up) and stable (pointing down) in data table 2, in the row for 1 shake. 4. Repeat step 3 nine more times. 5. Use a computer to graph the data. Follow instructions in the graphing software package or from your teacher in order to make the graphs. Plot the number of shakes on the x-axis and the number of unstable (points-up) thumbtacks on the y-axis. Data Table 2: Radioactive Decay of Thumbtacks Shakes | Unstable thumbtacks | Stable thumbtacks o | w 10 4 50 Analyze 1. What happens to the number of unstable pennies as the number of half-lives increases? 2. Approximately what percentage of pennies were removed after each half-life? Why do you think this was the case? 3. What does the shaking of the pennies represent? Would the amount of time spent shaking the pennies affect your data? 4. What happens to the number of unstable thumbtacks as time passes? 5. Compare the shapes of the two graphs. What are the similarities? What are the differences? Describe the shape of each graph. Draw Conclusions 1. Imagine that you repeat experiment 1 with a sample of 500 pennies. About how many pennies would still be unstable after 3 half-lives? 2. Does the number of shakes in experiment 2 represent the number of half-lives that have passed? Why or why not? 3. Let each shake of the pennies or thumbtacks represent 1 year. What is the half- life, in years, for the pennies in experiment 1? What is the half-life, in years, for the thumbtacks in experiment 2