lab half life assignment reflect on the lab

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Half Life Model

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While working in groups to facilitate peer tutoring, students manipulate a hands-on, physical model to better comprehend the nature of half life. Students use the model to simulate the decay of radionuclides. The resulting data are graphed and used to calculate ages in several hypothetical scenarios.

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Grade level.

Learning Goals

• The definition of a half life.
• That the number of decaying atoms changes with each half life but the percentage of decaying atoms remains constant.
• The random nature of radioactive decay.
• How to use half-life data to calculate the age of a given material.
• The age limits of using various radioisotopes.

Context for Use

Description and teaching materials.

• 50 small washers (per group)
• Gold spray paint
• One small ziplock bag
• One plastic "shoebox" container with a lid
• One red pencil
• One blue pencil
• Student handout

During a lecture, have the student groups place the washers into the box silver side up. (The silver side represents the parent and the gold side represents the daughter product.) Students record the number of silver washers (50 parent isotopes) in the box. After closing the lid, students shake the box five times, open the box and count the number of silver washers. After recording the number of silver washers in the box as well as the cumulative number of gold washers, the students remove the gold washers, replace the lid, and shake the box again. This process is repeated until zero silver washers in the box.

Students use the data collected and the colored pencils to graph the number of silver and gold washers for each trial and label each curve as the parent or daughter. They also answer an assessment question (See handout (Microsoft Word 40kB Aug19 08) ).

After debriefing the exercise, draw a graph using the average number from each trial. This curve will be very close to the theoretical value. (After our first semester of using this model, we used data from a previous class to calculate the average values for each trial.) Explain how any one group might have results that are different from the theoretical value, but when the data from the entire class are averaged together, the results match the expected values. This can lead into a discussion on the randomness of radioactive decay.

Teaching Notes and Tips

• They might shake their boxes an insufficient number of times. Encourage them to shake the boxes the same number for each trial.
• Near the end, some groups may become frustrated when their final washer refuses to land gold side up. Encourage them that this is normal and to keep repeating the process until they succeed.
• Some groups may loose a large percentage of washers in one trial. Explain to them that this is a normal consequence of the random nature of such events.
• If you have a personal response system, you can ask ConcepTest questions that focus on the definition or use of half life. (See References and Resources for sample ConcepTest questions)
• By walking around the class, the instructor can observe how well the groups comprehend the underlying concepts and ask individual students to explain their conceptual understanding
• Students could complete a worksheet containing questions about using half life
• Students could write a 'minute paper' explaining half life or how to use half life to calculate the age of a rock

References and Resources

• Einsteinium Half Life
• Percent Parent
• Parent-Daughter Ratio
• Radio Decay
• Penny Decay

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• Lesson Info

Investigate the decay of a radioactive substance. The half-life and the number of radioactive atoms can be adjusted, and theoretical or random decay can be observed. Data can be interpreted visually using a dynamic graph, a bar chart, and a table. Determine the half-lives of two sample isotopes as well as samples with randomly generated half-lives.

Lesson Materials

Student Exploration Sheet

Exploration Sheet Answer Key

Assessment Questions

Teacher Guide

Vocabulary Sheet

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Students model radioactive decay to determine the half-life of a “radioactive” sample.

Supports NGSS Performance Expectation 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.

Grade Level: High School

Subject: Chemistry

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Source Collection: Lab #19A

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Simulation Activity: Half-Life Investigation Mark as Favorite (31 Favorites)

ACTIVITY in Radiation , Half Lives , Radioactive Isotopes . Last updated July 25, 2023.

In this simulation, students will have the opportunity to investigate the decay of two samples of unstable atoms. Students will interact with the simulation in order to decay the unstable samples resulting in a visual and graphical interpretation of half-life.

Grade Level

High school

NGSS Alignment

This simulation 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.
• Using Mathematics and Computational Thinking
• Analyzing and Interpreting Data

AP Chemistry Curriculum Framework

This activity supports the following unit, topic and learning objective:

• TRA-3.C: Identify the rate law expression of a chemical reaction using data that show how the concentrations of reaction species change over time.

By the end of this simulation, students should be able to

• Indicate what happens to a sample size when it undergoes as half-life decay.
• Identify that radiation is emitted during the decay process.
• Determine the approximate sample size that will remain based on the length of a half-life for a given sample.
• Identify the shape of the graph produced during exponential decay.
• Define the meaning of “half-life.”

Chemistry Topics

This simulation supports students’ understanding of

• Nuclear Chemistry
• Half-life decay
• Radioactive Isotopes

Teacher Preparation : minimal

Lesson : 30-45 minutes

• Computer, tablet or phone with internet access
• Student Activity handout
• Half-life Investigation Simulation
• No specific safety precautions need to be observed for this activity.

Teacher Notes

• This simulation could be used in a teacher-lead lecture, or it could be used as a student activity.
• The number of particles available for selection in this simulation varies between 500 and 1000, and is used to show students a general example of how radioactive decay occurs. It is not meant to imply that a sample of this size could be visualized or quantified.
• It is recommended that students should be exposed to the concept of radioactivity and radioactive decay prior to using this simulation.
• In this simulation “Element X” and “Element Y” are not intended to represent a specific element from the periodic table. Instead, they are used with the intention of demonstrating the process of half-life decay. Students will determine that “Element X” must undergo 4 half-lives in order to reach stability, while “Element Y” must undergo 6 half-lives in order to reach stability.
• Please note that specific types of radioactive decay, such as alpha and beta decay are not discussed in this simulation.
• https://teachchemistry.org/periodical/issues/march-2017/half-life-investigation
• teachchemistry.org/half-life

For the Student

In this investigation you will investigate the radioactive decay of two element samples. Through your investigation you will be able to determine the number of half-lives that each element must undergo in order to reach stability. You will be asked to answer questions as you navigate through the steps of the simulation. You can find the simulation here: teachchemistry.org/half-life

Investigate

• Choose “Element X” to begin. Using the slider, choose a sample size. Record your initial sample size below:
• Select “Decay Sample.” Describe what happens to the sample size. What else occurs during the decay process?
• Continue to decay the sample until you arrive at stability. How many half-lives occurred in order for the sample to reach stability?
• If you started over with a larger sample size of Element X would you expect it to decay differently than this sample? (Ex: would it take more, less, or the same number of half-lives to reach stability?)
• Start over. Select a sample size of 812 particles, again for Element X. Complete the following table, predicting the outcome before using the simulation (omit any rows that are not necessary in the table).
• Use the simulation to verify your results for question 5.
• Start over. Now select “Element Y.” Choose a sample size. Record your initial sample size below:
• What do you expect to see happen when you click “decay sample”?
• Decay the sample of Element Y until it reaches stability. What did you notice about the decay of Element Y that was different than Element X?
• Consider the graphs created during the radioactive decay process of both Element X and Element Y. How were they the same? How were they different?

Applying what you learned

• In your own words define “half-life.”
• In your own words describe the meaning of “radioactive isotope.”
• Iodine-131 is a radioactive isotope, and is often used in certain medical treatments. It has a short half-life of about 8 days. If a hospital has a 750mg sample of it available, how much would be available after 48 days?
• Manganese-58 has a half-life of about 3 seconds. If you have a 90.0 gram sample, how long would you expect it to take to decay to approximately 1.40 grams?
• A 100.0 gram sample of Polonium-210 is contained for 552 days. How many half-lives occur during this period of time, if the half-life is 138 days?

Research the following terms: alpha decay , beta decay and gamma decay Briefly explain the meaning of each below: