Important terms to study from this lab assignment are colligative properties, membrane permeability and osmotic pressure. First, colligative properties are “those of a solution that depend solely on the number of solute particles present, not the identity of those solute particles. These properties include: vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure” (p. 17 lab manual). In this experiment freezing point depression is illustrated by comparing the freezing point of distilled water to the freezing point of distilled water mixed with a non volatile solute, salt. Another important term taken from this lab experiment is membrane permeability, which is the ability of the membrane to pass a solution through it. Membrane permeability is crucial in the effectiveness of dialysis. Lastly, osmotic pressure is “the pressure that must be applied to stop the movement of solvent through the membrane” (p. 19 lab manual). Membrane permeability and osmotic pressure is demonstrated by using the dialysis tubing when submerged in distilled water, and the raw egg when immersed in the Karo syrup.
One goal of this experiment is to understand the differences in freezing points of a pure solvent compared to a solution with salt. Another goal is to “observe the phenomenon of osmosis and gain a fundamental understanding of the principle on which dialysis is based” (p.15 lab manual).
Procedure (Part 1: Colligative Properties): To begin this experiment a water bath was assembled using a 100 mL beaker, and filling it half way with cool tap water. Then, crushed ice was placed in the remainder of the beaker just below the top. Salt was finally added to the beaker and the solution was stirred well. After, a test tube was filled with distilled water, and the temperature was recorded every 30 seconds until the temperature reading was steady for five consecutive 30