Using simple chemicals (NaOH) and phenylthalene, students will participate in an activity that demonstrates the rate of disease spreading through 2 populations of different densities. The activity will help students realize that disease is a density-dependent factor rather than a density-independent factor. By the end students will realize that diseases spread more quickly the more dense the population is by simulating populations. They enjoy finding out who "died" at the end and who survived! File includes teacher notes and an answer key.