Half-Life Lab Background Radioactive atoms decay by several methods so their nuclei can give off energy to become more stable. The rate of this decay is called the half-life. The half-life is defined as the amount of time it takes for half of the atoms in a sample of an isotope to decay into another element. The half-life is not an exact measurement because it is impossible to tell exactly when each atom decays, so it's what happens on average over a large sample of atoms of that isotope. This experiment will show you how decay really happens. When you flip a penny, there is a 50% chance that it will turn up "heads," and a 50% chance that it will turn up "tails." If you assume a penny that lands tails side up results in nuclear decay, then one flip of all of the coins should result in 50% of pennies landing on tails and would be the equivalent of one half-life. This experiment will familiarize you with how nuclear decay really occurs, and it will help you become more familiar with half-life calculations. Problem To mimic a radioactive isotope's half-life by flipping a coin. Materials A bag of 20 pennies Procedure 1. Record the bag number. Count the number of pennies in the bag. You should have 20 pennies to work with. 2. Shake and drop the pennies. Record how many pennies end up as heads. These are the atoms that did NOT decay and are still the original element. Set aside the pennies that fell tails side up because they represent the atoms that decayed into a different element. 3. Flip the remaining coins. Again, record the number of pennies that landed heads side up and set aside the tails side up pennies. 4. Repeat until you have zero pennies landed on heads. 5. Repeat steps 2-4 twice more to record a second and third trial of data. 6. Calculate the average number of atoms remaining, rounded to the nearest whole number, after each flip. 7. When you are finished, please make sure you still have all 20 pennies, put them back in the bag, and return it to your teacher. 8. Wash your hands after you have turned in your pennies - money is covered in germs