Activity Radioactive Decay

Activity- Radioactive Dating Using Half-Life Introduction: An Activity about Forensic Anthropology Scientists can use their knowledge of radioactive decay and half-lives to determine the age of many things, including skeletal remains. One method used to determine the age of bones is the Carbon-14 method. Carbon-14 is a radioactive isotope of carbon that is found in all living things. Carbon-14 is absorbed by living things when they are alive and although it does decay, it is constantly replaced. When an organism dies, the amount of C-14 begins to decay at a fixed rate determined by the half-life of the isotope. The half-life is the time it takes for ½ of a radioactive isotope to decay into a stable isotope. Scientists can measure the amount of C-14 remaining in a skeleton to determine how long ago an individual died. Purpose: Simulate the process of radioactive decay of a fictitious element, “boneyum”, found in bones Use your data to solve a forensic mystery Materials: Shoe box for each group, “radioactive atoms”, & data sheet Part I: Determine the ½ life of “boneyum” Procedure: 1. Place each of your 100 squares in a shoe box or container. These squares represent radioactive atoms. 2. Shake the box with one big shake to mix your atoms. Each shake represents 10 years of time. Dump the atoms on the desk in front of you. 3. Sort out & count all the atoms (or squares) that land with their radioactive side up. Record the number of radioactive atoms that remain on your table. Also, count the non-radioactive/ stable atoms (non-marked). These white atoms have decayed and turned into stable “daughter” atoms. Record this number in “# stable” section of your data table. 4. Put the remaining radioactive atoms back in the box and leave the stable ones off to the side, but include these in your total number of “stable” atoms after every round. 5. Shake the remaining radioactive atoms in the box again and dump out the atoms on your desk. Sort out & count all the atoms (or squares) that land with their radioactive side up. Record the number of radioactive atoms that remain on your table. Also, count the non-radioactive/ stable atoms (nonmarked). These white atoms have decayed and turned into stable “daughter” atoms. Record this number in “# stable” section of your data table. 6. Repeat steps until you don’t have any radioactive atoms remaining. Data/ Observations: (record on your own paper!!!) Start (time 0) # radioactive “parent” atoms # stable “daughter” atoms that decayed (non-marked) % of radioactive atoms remaining in box (radioactive/ total x 100) Shake 1 (10years) Shake 2 (20years) Shake 3 (30years) Shake 4 (40years) 100 0 100 % DO NOT WRITE ON THIS PAPER!! Shake 5 (50years) Shake 6 (60years) Part II- Determine the Missing Person Real- Life Application: The year was 1998. Some deer hunters stumbled across a suspicious-looking mound of dirt in a heavily wooded area in Stattonville, South Carolina. Crime scene investigators were called in to evaluate the scene. After determining that this might be a grave, the investigators ask for help from some forensic anthropologists. Working together, the site is carefully excavated. The skeletal remains of a human are found in the grave. The forensic anthropologists determine that the remains belonged to a female, about age 13. She had been shot at close range through the back of the head. X-rays are taken. Police records turn up missing person reports of ten girls this age. Anthropologist decide to narrow down the range of possibilities by determining how long the young girl has been dead. To do this they must do radioactive dating of the fictitious element “boneyum”. Purpose: Use the radioactive decay graph on “boneyum” from part I to solve the missing persons case. The missing person report: Name of Girl Hometown Date first reported missing Sue Crayton Rexty, SC 1964 Brenda Sills Tebvro, GA 1985 Jane Killow Loxton, AL 1945 Fay Johnson Sunville, TN 1935 Mary Sparks Mayfield, NC 1990 Linda Tims Brownton, SC 1933 Andrea Brown Troopville, GA 1985 Jay Sims Glexton, SC 1900 Kay Thomas Yexton, AL 1995 Leslie Andrews Freeport, NC 1920