M & M Decay

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Description:

This simulation is intended to help students use what they already know (elementary probability) to the concept of radioactive decay and how it can be used to determine the absolute age of an igneous rock. The students will be simulating atoms of a radioactive isotope such as radiocarbon or uranium with M & M's or some other flattish object with differently-marked sides. They simulate a half-life by shaking the M & M's and dropping them onto a sheet of paper. Roughly half of them will fall with the blank side up, just as half of the radioactive atoms decay into another element during a half-life. The students will remove the blank M & M's, graph the number of undecayed ones, and shake those, simulating another half-life. The students will pool their data, examine the effect of sample size, and assess how many half-lives it takes to run out of countable undecayed atoms. This model explains why real radiometric dating labs require minimal starting sample sizes and cannot give dates beyond a certain range (>40,000 yrs) for radiocarbon.