Archaeo-Tech: Radiocarbon Dating
Students explore the concept of radioactive decay and half-life through a penny-flipping activity, then learn how this principle is used in radiocarbon dating to estimate the age of ancient organic materials in archaeology. They also discuss the limitations of this dating technique.
Lesson Created By: MegGaillard
Lesson Partners: South Carolina Department of Natural Resources
Essential Question
How can scientists use the predictable decay of radioactive isotopes, like radiocarbon, to estimate the age of organic materials and revolutionize our understanding of the past?
Grade(s):
- 9
- 10
- 11
- 12
Subject(s):
Recommended Technology:
Other Instructional Materials or Notes:
Materials
• Activity 1:
o Half-Life & Radiocarbon Dating Worksheet (one for every student)
o 100 pennies per group
o One zip-lock plastic bag per group
• Activity 2:
o One scientific calculator per student
Lesson Progression
1. If necessary, review the structure and characteristics of atoms and their subatomic particles. Students should have a firm understanding of these basic
concepts before starting this lesson.
2. Distribute the “How Old Is It? Understanding Radiocarbon Dating” Lesson and Worksheet. Introduce the concepts of isotopes and radioactivity to your class. Students can follow along in the worksheet as they listen to the lecture.
3. Transition into a discussion on radioactive decay and half-life. Instruct your students that they will be simulating radioactive decay through a short activity
involving pennies (you don’t have to use pennies – any object with two distinguishable sides will work).
4. Divide your class into pairs or small groups, assign each group a number, and have your students complete “Activity 1” in their worksheet. On the board create a table for averaging the class results. As your students finish filling out their “Activity 1 Table”, have them submit their results to the class table and create a class average.
5. Graph the class average on the board. Have your students compare their group’s results to the class results.
6. Have your students complete the “Questions for Discussion” under “Activity 1” in their worksheet. Then discuss the activity as a class, emphasizing how this activity represents the concept of half-life. Explain that in the real world, the half-lives of radioactive isotopes can vary from less than a second to millions of years. Instruct your students that because half-life is a fixed rate of decay over time, it can used to measure how old something is.
7. Next, direct your student’s attention to “Part 2” of the worksheet. This part focuses on the application of radioactive decay and half-life in the field of archaeology. Show your students the Archaeo-Tech: Radiocarbon Dating film and have them answer the questions in their worksheet.
8. Discuss the film and the science behind radiocarbon dating. Students can follow along in their worksheets as they listen to the lecture / discussion. Have your students move on to “Activity 2: Radiocarbon Dating Exercises”. Introduce the formula for exponential decay, explaining each variable and how we can use this formula to model the decay of radiocarbon using our understanding of half-life. You can adjust the math skills used in this activity for different classes. Students in advanced classes can apply concepts learned from pre-calculus and calculus courses. Have your students solve the radiocarbon dating problems in their worksheet. This activity can be expanded to other isotopes and rates of decay.
9. Read and discuss the limitations of radiocarbon dating. Show your students the film Challenges in Radiocarbon Dating Aquatic Specimens via the link in the resources tab. Have them answer the following questions. Conclude the lesson by discussing the merits of radiocarbon dating.
Teacher Notes
extension: Have students read the article “The Shell Rings of Pockoy: A Window into the Past” by Cindy Thompson for the South Carolina Wildlife magazine. The article is linked in the resources tab. Discuss how radiocarbon dating was used by archaeologists studying the Pockoy Island Shell Ring and what information it revealed.
differentiation: Create a modified data collection sheet for struggling students. Instead of a blank table, provide a pre-drawn table with designated rows for each "flip" (round) and columns for recording the number of remaining "heads" (radioactive isotope).
Background Information
Reference this during the whole group portion of the lesson. Includes vocabulary terms.
View ResourceFilm & Activity Answers
Reference if needed for the follow up questions in the film and second task.
View ResourceRadiocarbon Dating
It's critical for an archaeologist to know the age of an artifact recovered from an excavation. To find out, they turn to radiocarbon dating.
View ResourceChallenges in Radiocarbon Dating Aquatic Specimens
Show this video for step 9 in the lesson sequence.
View ResourceStandards
- E-ESS1-6. Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earths formation and early history.
- RI.MC Meaning and Context
- RI.MC.6 Summarize key details and ideas to support analysis of central ideas.
- RI.MC Meaning and Context
- RI.MC.6 Summarize key details and ideas to support analysis of central ideas.
Assessments
Use the How Old Is It? Worksheet linked in the reosurces tab to assess student learning outcomes.
