Finally, it's down to the actual investigation. Students need to take care that they make accurate measurements, record their data, and perform enough repetitions to ensure a reliable data set. The minimum number of repetitions should be three to five. You may wish to review the document How do we ensure reliable measurements?
Students are likely to be quite excitable due to: the mentors' presence, performing hands-on activities and possibly being located outdoors. Safety awareness is crucial. Remind students to walk, take turns, remain calm and use quiet (indoor) voices.
The role of mentors
Mentors should be back in the classroom for their second visit by now. Having them around for the active and busy part of the GEMS process provides a valuable pair of hands and an important source of information. You may choose to have students perform some of their data collection (some of the repetitions) before the mentor visit if the investigations are particularly time consuming.