Osmosis through a semi-permeable membrane: effects of solution concentration on the weight of shelled eggsSolutions are single-phase homogeneous liquid mixtures consisting of a solvent - usually, but not always, the dominant substance and solute, the less prevalent substance. A dissolved substance will be distributed evenly throughout the solution, at the molecular level. The amount of solute per unit volume or mass of solution is called concentration. This quantity can be expressed as mass per mass of solution (percentage, g of solute per 100 g of solution) or in quantity per volume (molarity, mol/dm3). A semi-permeable membrane (or selectively permeable membrane) is a membrane that allows passage of certain substances between the compartments it divides, while preventing the passage of others. If two compartments containing solutions of different concentrations are divided by a semipermeable membrane, the entire system will attempt to reach equilibrium. The solution with the highest concentration of the solute is said to be hypertonic relative to the other solution, while the solution with the lowest concentration is said to be hypotonic. Since the system will attempt to balance the osmotic pressure on both sides of the membrane, the membrane will allow the passage of the substance for which it is selective. This process is known as osmosis and continues until an equilibrium is reached and both sides of the membrane contain solutions of equal osmotic pressure. Cell membranes are semi-permeable membranes. This is a complex model, as they allow the cell to maintain a constant content of certain solutes, using both passive and active transport to ensure the precise composition of the cytoplasm. There are many synthetic membranes that a...... middle of paper ...... is impossible in the hypotonic solution because the membrane would eventually break), i.e. until the eggs stop losing water and their mass becomes constant.ConclusionThe experiment shows qualitatively that two solutions of different osmotic pressures, separated by a semi-permeable membrane, will tend to balance their tonicity. In this particular case, an egg placed in a hypertonic solution will lose weight as it loses water, and placed in a hypotonic solution, will gain weight as water enters it. However, no quantitative assessment is possible from the data obtained in this experiment and further experimentation is needed to address these shortcomings. References Cited Stegall-Faulk, T. Kulkowski, M., Stewart, W. & Cobb, V. (2014) Biology 2011/2021 Human Anatomy and Physiology Laboratory Manual. Plymouth, Michigan: Hayden-McNeal Publishing.