Set up the three systems in a place where 8 students can comfortably observe each. These do not need be the same locations where the lamps are set up.

Assign one third of the class to be responsible for observing and reporting on one system, throughout the investigations. This is their "home" 2-bottle system. Students can also observe the systems for which they are not responsible.

Students annotate the line drawing of their "home" 2-bottle system on the [2-bottle closed systems - Initial Observation] page in their Science Notebooks. Refer students to Annotated Drawings at the back of their Science Notebooks for tips and reminders about making this kind of drawing.

Students use a second line drawing [Predict what will happen in the 2-bottle system?] to predict what their "home" 2-bottle system might look like in one week. The drawing will describe any changes they think might occur and explain the reasoning behind their predictions.

When students finish, put the lamps on the stands, secure them with rubber bands, and turn them on.