CH 221 Lab 4_A Popcorn Model for Radioisotopic Dating (2)

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Notre Dame College *

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221-4A

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Geology

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May 8, 2024

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docx

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A Popcorn Model for Radioisotopic Dating Procedure Adapted from: New Mexico Bureau of Geology & Mineral Resources New Mexico Institute of Mining & Technology Reading Assignment: Review Chapter 8 Materials 6 mini bags of microwave popcorn microwave (preferably with digital timer displaying seconds) stopwatch (only if microwave timer does not display seconds) Corresponding Popcorn Datasheet and Graph Procedure Using a microwave oven, pop 6 bags of popcorn one at a time. Label six bags with predetermined popping times t=0 sec, 10 sec, 20 sec, 30 sec, 40 sec, and 50 sec. Preset the microwave time for 2 minutes. Even though you will only be popping for a short time, some time will elapse as popcorn heats up and begins popping. The “radioactive decay” timing begins when you hear the first kernel of popcorn pop. Use the microwave timer or a stopwatch to measure the popping time. Turn the microwave off and remove the bag as soon as the predetermined (decay) popping time is reached. Now open your bag. Count the number of unpopped kernels and the number of popped popcorns in the bag. Record these numbers in the datasheet provided. Next, calculate the percentage of both unpopped kernels and popped popcorns in your bag. To do this, first divide the number of unpopped (parent element) kernels by the total number of kernels and popcorns in the bag. Next divide the number of popped (daughter element) kernels by the total number of kernels and popcorns. Multiply both fractions by 100%. Using your data, draw a graph on the provided handout. Let the horizontal axis represent time, from 0 to 60 seconds. Let the vertical axis represent the percentage of material in each your bags. First, plot the curve of percentages of unpopped kernels in all bags. This curve shows the “decay” of “parent” unpopped kernels over time. Next, plot percentages of popped popcorns in each bag. As the percentage of “parent” kernels gets smaller over time, what happens to the percentage of “daughter” popcorns?
The two curves should intersect on your graph at the 50 percent point on the vertical axis. What is the corresponding point on the horizontal axis, which represents time? This is the half-life of your kernel- popcorn material." Response How do scientists use the half-lives of isotopes to understand the geologic record? Although scientists can calculate the half life of certain isotopes for dating purposes, what assumptions must be made about this dating method? Complete a brief web-search using the key words “assumptions to radiometric or radioisotopic dating” and write down what you found. Does this change your perspective on the reliability of the radioisotopic dating method? Finally, review the following journal article from Nature Communications. Nature is one of the most prestigious publishers of scientific journals in the world and this article has raised more than just a little attention. Please respond to the following questions o What is the main point the authors are conveying? o What main assumption does the article make about their main finding? Do their findings prove/disprove the accepted age of dinosaurs? o What do you think of the findings? Does it surprise you? Link : https://www.nature.com/articles/ncomms8352
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