Jube's Water Potential and Molarity Mixup Lab

      When a substance is placed in a solution, the higher the percent change,the higher the molarity; in this lab, the dark green solution had the lowest molarity, and the red solution had the most. Molarity is a measure of the solute in a solution. The greater the increase was in the  the vegetable’s weight in activity 2, the higher the molarity. If the solution was hypotonic, the solution caused the eggplant to become very firm. However, if the solution was hypertonic, the eggplant became squishy. Evidently, the eggplant in the dark green solution was the firmest. Since the dark green solution was able to move water into the eggplant, the water concentration in the eggplant was less than the water concentration in the solution. Essentially, since water moves from high concentration to low concentration, there must have been a minimal amount of solute in the dark green solution. Hence, the dark green solution was hypotonic. Likewise, the eggplant in the red solution was the squishiest one when compared to the five other eggplants used in this lab. Due to its high molarity, the water concentration in the solution was less than the water concentration in the eggplant. Therefore, the red solution was a hypertonic solution. The data collected by my group and I supports this.

In activity two, twelve cups contained each of the solution. Six of the cups had a small piece of eggplant in them while the other six had a small piece of okra in them. My group and I measured the initial and final weight of the vegetables and calculated the percent change. The percent change was calculated by subtracting the new weight from the initial weight, then dividing that by the initial weight. This was then multiplied by 100 to get the percentage.  In the red solution, the initial mass of the eggplant it contained was 9.9g and its new weight was 8.1g after spending some time in the solution. Thus, the percent change was -18.2%. The initial mass of the eggplant in the yellow solution was 9.9g and its final mass was 8.6g which resulted in a -13.1% change. The eggplant in the orange solution had an initial weight of 9.9g which decreased to 9.1g after being placed in the solution for several hours to account for a percent change of -8.1%. The initial weight of the eggplant in the light green solution was 10.2g but it decreased to 9.8g which led to a -3.9% change in its weight. The eggplant in the blue solution had an initial mass of 9.4g and it increased to 10.1g which led to a 7.4% change. The eggplant contained in the dark green solution had an initial weight of 11.5g and a new weight of 14.1 which led to a 22.6% change. The results of the eggplant data allowed my group and I to calculate the molarity of eggplant solutes which was .335 grams. In addition, we were able to find the solute and water potential which turned out to be -8.240196 bars. To calculate this, we used the water potential equation (water potential = -iCRT). The chart below shows the percent change calculated for the eggplant data.

         This data is important because it shows the relative changes in the weight of the vegetables as a result of the solution it was placed in. The results helped determine the molarities of each solution. The higher, the change, the greater the molarity, and solutions with greater molarity had less water which caused the water to move from higher concentration (the vegetable) to lower concentration (the solution). As a result, the vegetable became softer because they lost water. In comparison, the data shows that the more negative the percent change, the less molarity the solution had. In this case, the solution would have more water than solutes. As a result, the water would go from an area of higher concentration (the solution) to an area of lower concentration (the vegetable). As a result, the vegetable would become firmer.

 

Essentially, we determined that the molarity of the solutions is as follows:

0M= Dark Green .2M= Blue .4M= Light Green .6M= Orange .8M= Yellow 1.0M= Red

The other six cups were used to measure the changes in the mass of the okra. However, the results that my group and I came up with showed that the solutions are all hypotonic to the okra because all of the okra increased. This may have been due to the fact that okra naturally develops a gooey consistency when heated or placed in liquid for some time. This may have added to the mass of the okra. Therefore, the data collected for the okra does not really reflect the claim stated above that the dark green solution has the lowest molarity (0M), and the red solution has the highest molarity (1.0M). The graph constructed does not cross the x axis. Hence, the molarity of the okra solutes can only be inferred.  

            Furthermore, activity 1 supports the claim that the dark green solution has the greatest molarity. The solutions were placed in the dialysis tubing, and then they were placed in water. The higher the percent change in the mass of the dialysis tubing contents, the greater the molarity. The results in order of high molarity to low molarity are as follows (followed by percent change): yellow (52.3%), blue (31.4%), light green (14.8%), orange (12.7%), red (1.9%), and dark green (-26.2%). In comparison, the results of the data collected in activity 2 in order of high molarity to low molarity are as follows: red, yellow, orange, light green, blue, and dark green. Evidently, there are many differences in the results from both activities. For instance,the red solution has one of the lowest molarities in activity 1. This could simply be due to error. The results would have been more accurate if the water was distilled. Since we used tap water in this lab, there may have been chemicals and other substances which could have potentially altered the results. If the water was 100% distilled water, there would be less differences between the data collected from both activities. Nevertheless, the dark green solution did have the most decrease in the mass of the contents contained in the dialysis tubing.