i) The size of the cell will increase when placed in a hypotonic solution. This occurs due to the phenomenon of osmosis or endosmosis, wherein water moves from its higher potential to its lower potential, that is from a solution with lesser concentration (hypotonic) of solutes to a solution of greater concentration of solutes (hypertonic). Here, water moves into the cell and the cell swells due to endosmosis.
ii) The size of the cell will decrease when placed in a hypertonic solution. This occurs due to the phenomeonon of osmosis or exosmosis, wherein, the water will move out of the cell to the exterior, resulting in the shrinking of the cell. This occurs because the water potential of the solution exterior to the cell is lower than inside the cell or the solute concentration of the solution is greater than the solution inside the cell
iii) The size of the cell remains the same when placed in an isotonic solution. This is because both the inside and outside of the cell are in the same concentration with respect to water and solutes Hence,there there will be no net movement of water.