Yam is used in this set-up because it acts as a semi-permeable membrane. In this setup, yam is used as a model for understanding osmosis, which is the movement of water molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration. In this experiment, the yam serves as the semi-permeable membrane that separates the two salt solutions of different concentrations. The yam allows the movement of water molecules, but not the salt molecules, thus facilitating the movement of water from the region of lower salt concentration to the region of higher salt concentration. Therefore, yam is used in this set-up because of its semi-permeable nature, which enables the experiment to study the process of osmosis.
