MOS, or Minds-On-Science, is the foundation of conducting educationally valuable science demonstrations. It is a teaching strategy equally effective as hands-on-learning. Plus, it proves much more effective at reinforcing abstract science concepts than traditional lectures, readings, and audiovisual presentations. Adding MOS to a demonstration simply means turning the demonstration into an inquiry activity. However, even with the best-designed demonstration it must not be assumed that students have gained value from the inquiry session unless they are assessed during and after the activity.