To demonstrate that the rates of decay of unstable nuclei can be measured, that the exact time that a certain nucleus will decay cannot be predicted, and that it takes a very large number of nuclei to find the rate of decay.
To do this lesson and understand half-life and rates of radioactive decay, students should understand ratios and the multiplication of fractions, and be somewhat comfortable with probability.Games with manipulative or computer simulations should help them in getting the idea of how a constant proportional rate of decay is consistent with declining measures that only gradually approach zero.The mathematics of inferring backwards from measurements to age is not appropriate for most students.They need only know that such calculations are possible. 79.) In this lesson, students will be asked to simulate radioactive decay by pouring small candies, such as plain M&M's® or Skittles®, from a cup and counting which candies fall with their manufacturer's mark down or up.The exercise they will go through of predicting and successively counting the number of remaining "mark-side up" candies should help them understand that rates of decay of unstable nuclei can be measured; that the exact time that a certain nucleus will decay cannot be predicted; and that it takes a very large number of nuclei to find the rate of decay.
This lesson can be done in two, 45-minute class periods.It may be combined with the Frosty the Snowman Meets His Demise: An Analogy to Carbon Dating, which can be done while students are flipping their candies.In your planning, be sure to include time at the end of the lesson for students to post their data and share the class data.Before the lesson, you will have to weigh out about 80 candies for each group of students.If you count ten and weigh them, then multiply by 8, you will know how many grams of candy to weigh out for each group.To help students understand the history of radioactivity, have them go to Radioactivity: Historical Figures, on the Access Excellence Classic Collection site, to read about the contributions of Wilhelm Roentgen, Antoine Becquerel, Marie and Pierre Curie, and Ernest Rutherford.