Lesson Plan 1.0 Major Understanding 2.0 Objectives Use a radiation monitor to detect emission from naturally occurring radioactive sub-

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1 Lesson Plan 1.0 Major Understanding 2.0 Objectives M M M M ome chemical elements are unstable and breakdown to release particles and rays of energy. Each element has a characteristic half-life or time in which half of it decays. Radioactivity can be measured using various types of Geiger counters including the Vernier tudent Radiation Monitor. The time-dependent relationship of radioactivity decay can be graphically analyzed and modeled with equations. Use a radiation monitor to detect emission from naturally occurring radioactive substances (optional experiment). Graph data on the radioactivity of dust over time, describe the pattern, and offer an explanation. Write an equation to represent the graphical pattern and use it to solve practical problems. Use the following terms correctly and apply them to the interpretation of data: radioactive decay, alpha particle, beta particle, gamma ray, Geiger Counter, half-life, scatter plot, exponential function, logarithmic function. Design and conduct additional experiments to explore variables affecting radioactivity (extension). Determine the half-life of a collection of radon decay products. 3.0 Time 3.1 Data Collection: minutes 3.2 Data Capture: 2 hours 3.3 Data Analysis: minutes 3.4 Data Interpretation and Conclusion: 30 minutes It is recommended that this lesson be divided into two sessions: the first for data collection and PowerPoint Presentation and the second, for data analysis, interpretation, and conclusion. Data capture, which involves using the tudent Radiation Monitor, CBL, and TI-83 Plus Graphing Calculator, can be started by students on the first day and allowed to run until finished. Devices will automatically turn themselves off. 4.0 Materials TI- 83 Plus Graphing Calculator RADIATIN Calculator Program Balloon tring CBL Vernier Radiation Monitor or tudent Radiation Monitor TI-GRAPH LINK TI-Interactive (optional) TI-Black link cable continued

2 5.0 tate and National Correlations Virginia tandards of Learning: Chemistry (CH.1, CH.6); physics (PH.1, PH.2, PH.4); Algebra II (AII.9) and Math Analysis (MA.9). NCTM tandards: modeling data. scatter plots, bivariate data, functions, transformations, NE tandards: radioactive isotopes, decay, prediction of age of materials. 6.0 Instructional trategies 6.1 Anticipatory et Divide the class into groups of 3 or 4 students. Have each group list sources of radiation to which they have been exposed over the course of their lifetime. Have students write their responses on the board. Then ask students to circle the sources of radiation that they think pose the greatest risk to their health. Does the risk depend on other factors, such as geographic location or frequency of exposure? 6.2 Background Information Instruct students to review the information on-line or present a mini-lecture using the PowerPoint presentation. 6.3 Conduct the lab, "Radiation In the Dust." If you do not have the equipment or time, use the ample Data et. Data collection will be made using balloons that have been given a static charge. Because of static electricity, the dust particles should adhere to the balloon. If you do not get radiation counts above the background level, the humidity may be too high for a good static charge build up or the volume of radon gas may be too low. Remind students to subtract the background count from all radiation monitor readings. The difference is the radiation count attributable to the radon by-products. 6.4 Data Analysis, Interpretation, and Conclusion Have students use the data on their graphing calculator or load the data set into Excel, TI-Interactive or Fathom Follow procedures for Data Analysis, Interpretation, and Conclusion. The dust sample collected by the balloon is not a single nuclear species decaying to a stable state. Therefore, the graph of the decay curve is not a single exponential function, but the sum of several related exponential functions. The half-life calculated does not correspond to any one decay element. The value of the effective halflife will depend on the length of time the balloon is allowed to collect dust and the time between deflating the balloon and beginning the data collection. From the radioactive decay table, students can infer which isotopes contribute the sample on their balloon, e.g. Polonium -214, Lead -214, Bismuth 214, and Polonium Practice 8.0 Closure 7.1 Use "Check Your Understanding." 7.2 Provide students with the ample Data et. Have them analyzed it. Do the data represent radon decay products? If not, what products are represented? Review objectives and relate to the learning experience. Re-teach if necessary. Encourage continued learning through the extensions and resources. continued

3 9.0 Extensions 9.1 Encourage students to extend their learning by investigating the affect of shielding or location on radiation count and to construct mathematical models. hields that absorb alpha, beta, or gamma rays should lower the radiation count. Unless there is a location with a very high radon concentration, students will generally find that the background count rate is independent of location within the school. If the school has a basement, the background counts in the basement may be higher than other locations since radon is a heavy gas and tends to collect in lower elevations. If the school is composed of various separate buildings, some of these buildings may act as better shields against cosmic radiation. 9.2 Utilize the listed resources to customize learning for your curriculum or individual students. 9.3 Possible solutions to Extensions. 1. Repeat the experiment, except this time place a piece of cardboard between the balloon and the tudent Radiation Monitor. Are the results dramatically different? Why? Answer: The answer should be yes since the cardboard acts as an absorber of radiation, especially alpha and beta particles, and therefore shields these particles from the monitor. 2. Using the tudent Radiation Monitor, determine if there is a variation in the background radiation count rate at different locations in the school. If this is so, why? If not, list reasons. Answer: Unless there is a location with a very high radon concentration, students will generally find that the background count rate is independent of location within the school. If the school has a basement, the background counts in the basement may be higher than other locations since radon is a heavy gas and tends to collect in lower elevations. If the school is composed of various separate buildings, some of these buildings may act as better shields against cosmic radiation. 3. What factors that you think influence background radiation? Design an experiment to test your hypothesis. Answer: Answers may vary. Location, radiation shielding 4. The half-life of the radioactive isotope bismuth is 5.01 days. If 3.2 kg are present now, how much will be present after 20 days? Answer: A = A 0 e kt.5 = e 5.01 * k ln(.5) = ln e 5.01 * k ln(.5) / 5.01 = k k = (decay constant) y = 3.2 e y = kg (5.01 * 20)

4 10.0 Assessment ample items are provided for use in checking student understanding or test construction. Objective Multiple Choice (Check Your Understanding) Extended Answer Use a radiation counter to detect emissions from naturally occurring radioactive substances. 13 Graph data on the radioactivity of dust over time, describe the pattern and offer an explanation. 10, 11, 12 9, 18 Write an equation to represent the graphical pattern and use it to solve practical problems. 10, 11, 12 13, 14, 15 Use the following terms correctly and apply them to the interpretation of data: radioactivity decay, alpha particle, beta particle, gamma ray, Geiger counter, half-life, scatter plot, exponential function, logarithmic function. 1, 2, 4, 6, 7, 8 15, 16 Design and conduct additional experiments to explore variables affecting radioactivity (extension). 17

5 Assessment Multiple Choice 1. What is the most common form of radiation that humans are exposed to? a. Gamma rays b. unlight c. Cosmic rays d. X-Rays 2. Energy levels of radiation higher than ultraviolet are called: a. Gamma b. Atomic c. Polarizing d. Ionizing 3. What is the primary source of background radiation? a. Cosmic radiation from the un and exploding stars b. Particles and rays given off as a result of the decay of large amounts of uranium present in rocks and soil c. Microwave energy from the communication industry d. Both (a) and (b) 4. Radon is a radioactive decay by-product of what element? a. Uranium b. Plutonium c. Lead d. Radium 5. Which phrase best completes the following statement? If you inhale radon gas into your lungs over a long period of time a. It poses no serious health problem. b. You will develop a resistance to it. c. It increases your risk of developing lung cancer.

6 6. What is the spontaneous disintegration of the nucleus of unstable atoms, such as uranium, by emission of alpha particles, beta particles and gamma rays, is called? a. Nuclear fission b. Adaptation c. Radioactive decay d. Chemical reaction 7. Half-life is: a. The time it takes for half of a given quantity of a radioactive substance to decay. b. The maximum life expectancy of one-half of the people involved in mining uranium c. One-half of the time required for a radioactive element to decay to a stable element d. None of the above 8. Why should the radioactive dust particles adhere to the balloon? a. The balloon becomes statically charged due to air flow in the room b. The balloon's outer surface is sticky. c. The dust particles have the opposite charge from that of the statically charged balloon. d. All of the above 9. Why was the option selected to subtract the background count from all of the radiation monitor readings? a. To normalize all of the tudent Radiation Monitors b. To have data values that represent radiation levels attributable only to the radon by-products c. To adjust for weather conditions d. To reduce the values for ease in calculations 10. What percentage of the initial activity of your sample would remain after five hours, if you were to continue the experiment for that length of time? a. 50% b. 15% c. 6% d. 12.9%

7 11. After 2 years, a sample of radon-222 has decayed 69.6% of its original volume. Find the half-life of radon. a..18 years b. 2 years c..03 years d years 12. Polonium-218 is a by-product of radon-222. Polonium-218 has a half-life of 3.05 minutes. At what rate does the substance decay? a per minute b per minute c per minute d per minute 13. The graph shows the rate count of radon present after t minutes. What is the approximate halflife of radon-222? a. 98 minutes b. 100 minutes c. 50 minutes d. 168 minutes

8 Additional Questions 14. Why did we select the option to subtract the background count from all of the radiation monitor readings? 15. Why is the calculated half-life inconsistent withany single half-life shown in the U238 Radioactive Decay chart? 16. From your experiment and analysis of the data, would you assume that there is a continuous source of fresh radon gas in the local environment? Why? 17. Radon emits an alpha particle to become polonium-218. Polonium-218 decays exponentially with a half-life of about 3.05 minutes. Construct an exponential function that shows the remaining amount of polonium as a function of time as 100 grams of polonium decays. Be sure to identify the units for your variables.

9 Assessment olutions 14. Why did we select the option to subtract the background count from all of the radiation monitor readings? In order to have data values that represented the radiation counts attributable only to the radon by-products. 15. Why is the calculated half-life inconsistent with any single half-life shown in the U238 Radioactive Decay chart? The calculated half-life is significantly longer than any of the individual half-lives of the radon decay by-products. Therefore, we can conclude that we are observing a combination of decays from several products. 16. From your experiment and analysis of the data, would you assume that there is a continuous source of fresh radon gas in the local environment? Why? Yes. If we assume that the radioactive dust collected by the balloon consisted of radon decay by-products, then there must be a continuous re-supply of radon into the environment. If this were not the case, then the radon decay by-products would have long ago decayed. 17. Radon emits an alpha particle to become polonium 218. Polonium-218 decays exponentially with a half-line of about 3.05 minutes. Construct an exponential function that shows the remaining amount of polonium as a function of time as 100 grams of polonium decays. Be sure to identify the units for your variables. A= A 0 e kt y = 100 * e 3.05k y number of grams of polonium remaining t = time (in minutes) Hint: olve for k