Absolute Concentration Lab Report

The Effect of Solute Concentration on the Mass of Apples
Introduction
Background:
This lab involves the testing and measuring of water potential. Water potential (ψ) is the tendency of water to diffuse from one region to another. It measures the free energy available in water to do work. Pure water has a water potential of 0 (kpa--unit?). Water will move from an area of higher water potential to an area of lower water potential. Several factors, including temperature, pressure (ψp) and solute concentration (ψs) contribute to water potential. (citation-lab) The equation to determine water potential is: ψ = ψp + ψs
Because the pressure potential is constant in this experiment, it does not need to be included in the equation and subsequent calculations.
Objectives:
The objectives of this experiment are to determine the water potential of apple cells and to better understand the movement of water through cells. This will be done by putting cores of apple tissue in sucrose solutions of different concentrations and measuring the changes in mass of the apple cores. The changes in mass reflect the movement of water into or out of the tissue. After determining the concentration of sucrose solution at which there is no net gain or loss of water from the apple tissue, the osmotic potential can be calculated. This will then tell the water potential of the apple cells.
Research Question and Hypothesis: How will changing the concentration of sucrose in solutions impact the mass of apple tissue submerged in the solution, and at what concentration will the sucrose solution and apple cores reach
There were six sucrose solutions: 0.0 M (distilled water), 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. The dependent variable was the mass of the cores of apple tissue. Changes in the dependent variable were measured by weighing the mass of each set of apple cores before and after its submerging in sucrose solution. The initial mass was then subtracted from the final mass and divided by the initial mass to calculate the percent change of each set. Changes in the dependent variable were analyzed in the form of percent change of mass rather than change in mass in grams because each set of apple cylinders had a different initial weight, so calculating percent change helped standardize the data. The control of the experiment was the distilled water because it has a molarity of 0.0 M, meaning that no sucrose is added to it. Several variables were held constant. It was attempted to keep the size of each core of apple tissue constant. Other constants include the ruler and scale used to measure the apple cores, as well as the knife used to cut the