In this activity, leads the students in understanding of half- life, exponential radioactive decay and how to find the age of the rocks by creating and interpreting a graphs. Students simulate radioactive decay of Ar-K with kernels and popped corn in a microwave popcorn bag as a “kernelite/popcornium” system. They count the number of kernels and popped corn, plot the “decay” curve of kernelite and the “accumulation” curve of popcornium, and use these curves to establish the “half-life” of kernelite. Then they determine the “age” (popping time) unknown popcorn bag. The learning activity provides the lesson outline, student handout, and links to background information to be used by the instructor.