All "out-of-class" assignments are subject to "unauthorized collaboration." Preventing this activity is almost impossible and detecting it can be time-consuming and frustrating . . . . so, why not "accept" this activity. If we focus on the "goal" of these assignments, perhaps we can create a learning environment that includes, even encourages, collaboration and still accomplishes the goal that students learn. Learning is defined as a change in long-term memory - if long-term memory has not been altered, then learning has not occurred.
How is this accomplished?
Inform students that they are allowed to collaborate with their peers, but that the goal of the collaboration is to learn how to solve the lab calculations. To determine if this goal was met, there will be a "timed calculation quiz" during the first 10-15 minutes of the next lab period where students log in to Chem21Labs and click on an assignment where random numbers have replaced the lab data from last week's lab - the lab they just completed the night before. If they "learned" from their collaboration, they can easily complete this quiz. To emphasize the importance of "learning" and not just "copying answers," make the "out-of-class" lab calculations ~30% of the lab report grade and this "in-class" assignment also worth ~30% of the lab report grade (the pre-lab assignment, safety/cleanup, balanced equations and essay answers comprise the remaining 40%). With this approach, instructors can establish a learning environment that places a high importance on "learning how to get the correct answer" and not on "getting the correct answer." Instead of fighting a battle that can't be won (i.e. preventing unauthorized collaboration), change the rules of engagement . . . . a WIN WIN for everyone.