This is a lab activity I used with alternative education students taking a human disease course. This could be used with younger students (5th - 6th graders), general biology students, or students in a health class.
The lab experiment is a structured inquiry lab that allows students to investigate bacterial growth on their cell phones. It includes a full pre-lab and lab sheet for students as well as a teacher guide on where to purchase and how to prepare lab materials. In addition, it includes a full answer key to both the pre-lab and lab (including tips on how to implement the lesson).
The lesson takes about 15 minutes the first day, 30 minutes the second set-up day, and an additional 30 minutes to wrap it up after their plates are allowed to grow.