Module 8
1. Module 8
1.10. Lesson 2
Module 8—Nuclear Decay, Energy, and the Standard Model of the Atom
Lesson 2—Decay Rates and Radioactive Dating
Get Focused
© Frank Slide Interpretive Centre. Used with permission.
The Burmis Tree, Crowsnest Pass, Alberta
Heading west on Highway 3 near the Crowsnest Pass, you will find one of Alberta’s most famous and most photographed trees. This limber pine, called the Burmis Tree, is more than 300 years old. It was a seedling in the late 1600s and died in 1978. It toppled over 20 years later in 1998. It has since been restored to its original position and is symbolic of the resiliency needed to survive in the unforgiving environment of the eastern Rocky Mountain slopes of Alberta.
The appeal of this natural landmark is its extreme age. Its gnarled branches have withstood more than 300 Alberta winters and countless days of high winds, drought, intense heat, and chilling cold. How could you know that this tree really is that old? How could you know when, and for how long, a tree has lived? How could you accurately determine when it died?
The unstable nuclei of the carbon isotopes in the tree, or any carbon-based organism, provide a built-in clock that can be observed to determine its age. When the tree was alive, the process of photosynthesis extracted radioactive carbon-14 from the atmosphere and fixed it into the tissue of the tree. When it died, the process stopped. As you observed in Module 8: Lesson 1, the carbon-14 nuclei will undergo beta decay to form nitrogen-14. Due to this decay, the amount of carbon-14 in the tissue decreases over time. By comparing the current amount of carbon-14 in the tissue to that of the carbon-14 that was present when the organism formed, it is possible to determine an age. Of course, this is only possible if you first know how fast, or at what rate, the carbon-14 nuclei in the tree decayed.
In Lesson 2 you will explore the rate of decay and its application in radioactive dating.
In this lesson you will focus on answering the following essential questions:
- What is a half-life?
- How are half-lives used to determine age?
Module 8: Lesson 2 Assignment
Your teacher-marked Module 8: Lesson 2 Assignment requires you to submit responses to the following:
- Lab—LAB 1, LAB 2, LAB 3, LAB 4, LAB 5, LAB 6, LAB 7, LAB 8, and LAB 9
- Reflect and Connect—RC 1 and RC 2
The other questions in this lesson are not marked by the teacher; however, you should still answer these questions. The Self-Check and Try This questions are placed in this lesson to help you review important information and build key concepts that may be applied in future lessons.
After a discussion with your teacher, you must decide what to do with the questions that are not part of your assignment. For example, you may decide to submit to your teacher the responses to Try This questions that are not marked. You should record the answers to all questions in this lesson and place those answers in your course folder.