Background: A student has a solution of an unknown concentration (Solution X). They want to find the relative concentration of Solution X using the process of transport across a membrane. They set up the following experiment. Materials: - 3 beakers - Balloons with semi-permeable membranes filled with Solution X - 3 solutions with different concentrations (high, medium and low concentration) Summary: The student sets up the three beakers each with a different concentrations of solution (high, medium and low). They place a balloon in each beaker. Each balloon contains the same volume Solution X . The balloon is permeable to water but not the solute. The dots represent the solute. The set-up is illustrated below: Variables: Identify the manipulated, responding and controlled variables:.