The Effects of Concentration on Osmosis

Introduction:

This experiment was used to examine the hypothesis that: Osmosis is dependent on the concentrations of the substances involved.

Diffusion is the passage of solute molecules from an area of high concentration to an area of low concentration (Campbell & Reece, 2005). An example is ammonia diffusing throughout a room. A solute is one of two components in a chemical solution. The solute is the substance dissolved in the solution. The solvent, the other component, is any liquid in which the solute can be dissolved (Anderson, 2002). Diffusion requires little or no energy because molecules are always randomly moving; this is due to their kinetic energy. Diffusion occurs only when there is an imbalance in the areas of concentration. The difference in concentration of molecules over a distance is known as a concentration gradient (Enger, Ross, & Bailey, 2005). Furthermore, net movement relates to the movement of molecules in one direction minus the movement of molecules in the other direction. Finally, if movement in one direction equals movement in the other direction then dynamic equilibrium occurs (Enger, Ross, & Bailey, 2005).

The diffusion of water molecules across a selectively permeable membrane involves a special form of diffusion called osmosis. When the external and internal solute concentration are equal, there is no movement of water will be observed. This is described as isotonic. Osmosis does not occur in an isotonic solution, because the concentrations are equal on both sides of the membrane and there is no net movement of molecules from one side of the membrane to the other (Payne, 2007). A hypotonic solution is a solution in which the concentration of dissolved substances is lower than the concentration inside the cell (Payne, 2007). If a cell is put into a hypotonic solution, osmosis will cause water to move from the through the cell membrane into the cell. A solution is hypertonic if its concentration of dissolved substances is greater than the concentration inside the cell (Payne, 2007). If a cell placed in a hypertonic