The phrase identifies a resource containing solutions or model responses for laboratory exercises focused on the movement of substances across a selective barrier. Such exercises typically involve observing or measuring the passage of molecules from an area of high concentration to an area of low concentration through a thin layer, such as a dialysis tube or a cell membrane model. For example, a laboratory experiment might involve placing a bag of concentrated starch solution into a beaker of water and using an iodine test to determine if starch molecules, which are too large to pass through the membrane pores, have diffused into the surrounding water.
Access to accurately worked-out solutions provides multiple benefits in an educational context. It enables students to check their understanding, identify errors in their experimental technique or data interpretation, and reinforce learning. Furthermore, instructors can utilize this type of resource to efficiently grade assignments, provide targeted feedback, and ensure consistency in assessment. Historically, providing students with worked solutions has proven an effective method of promoting self-directed learning and improving problem-solving skills within science education. The availability of such resources in digital format facilitates widespread access and ease of distribution.
