In this lesson, students will review the concept of isotopes and apply the concepts of stability and relative abundance in order to determine the recent travels of a person of interest in a criminal investigation.
This activity will help prepare your students to meet the performance expectations in the following standards:
- HS-PS1-8: Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay.
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
- Engaging in Argument from Evidence
By the end of this lesson, students should be able to
- Calculate the number of subatomic particles in different isotopes
- Calculate an element’s atomic mass based on relative abundance and mass numbers
- Define stable isotope
- Predict the origin of materials based on isotope analysis
This lesson supports students’ understanding of
- subatomic particles
- atomic mass
- relative abundance
- nuclear stability
Teacher Preparation: 15 minutes
Lesson: 60 minutes (about 20 minutes per worksheet)
- Three student worksheets per student
- Internet access or COLOR copies or projector
- Computer, tablet or phone with internet access
No safety precautions needed
- The majority of this activity is a standard review of subatomic particles and initial lessons in isotopes and relative abundance.
- The “Isotopes & Calculating Average Atomic Mass” Simulation is used to help students calculate atomic mass.
- Teacher may wish to stop before extension and give examples of how the stable isotope maps work, perhaps pulling in another example (strontium example is listed in references) – this is particularly good for extensions. More information about the maps can be found in the “Teacher Notes 1” download in the sidebar.
- In the maps used, the ratios (R) are for hydrogen (2H/1H) and oxygen (18O/16O). In most of the US, there is less deuterium than in the standard (δ2H is negative); there is more 18O than in the standard (δ18O is positive).
- The problem given on the worksheet is a bit more complex. A hair is found at a crime scene in central Wyoming. This area is part of the very dark blue sections of both maps and is a distinctive geographic region. The analysis of the hair shows that the end (the oldest part) originates from a bright red region in both maps – again distinctive.
- It is suggested that the teacher takes the students through a few different places – figuring out the deltas for those locations. Then, start the map, showing how the first one is from a dark blue area on both maps and locating that area.
- There are many potential paths through the US, but the source can only be Central Texas.There is one very logical straight line, but if a student supports his or her path with the correct isotope data, the student’s path should be considered correct. This is the path I drew (expand to see white dot path: