The experiment consists of putting a fruit or vegetable into six cups weighing 56.7 grams each. These cups will have varying sucrose molarities – 0, 0.2, 0.4, 0.6, 0.8, and 1.0. Each produce variable will undergo five trials, resulting in a total of 30 cups. The water potential of the produce is the dependent variable and will be determined by identifying the isotonic state using a line graph. The experiment also includes controlled variables.
Each variable produce used in the experiment is of the same type. The types of produce used include Russet potatoes, Pascal celery, Gala apple, Naval orange, and an Imperator carrot. For each trial, each piece of produce was completely submerged in 24 ml (measured with a graduated syringe) of a specific solution, either distilled water or sucrose of a specific molarity. It is important that the produce is fully submerged to ensure accurate measurements of mass difference and water potential. While submerged, the produce received no light. To prevent the sucrose or water from evaporating, the 56.7 gram cups containing the produce were covered with aluminum foil.
All produce samples were weighed using a digital gram scale to ensure accuracy and avoid mistakes. The water potential of each sample will be determined by calculating the percentage change in mass for each sample in different solutions. Thus, it is not necessary for all samples to have equal weights, as the emphasis is on the percentage change rather than absolute mass. To prevent dehydration and wilting of produce cells due to air exposure, the samples are promptly transferred to their designated solution cups after weighing. Additionally, transportation is done exclusively with tweezers to prevent any weight alteration caused by hand oil.
Hypothesis: We hypothesize that there will be no significant difference in water potential (within a range of .05 bars) among the five types of produce: carrot, celery, potato, orange, and apple. When these produce items are placed in solutions of distilled water, .2-molarity sucrose, and .4-molarity sucrose, they are expected to gain weight due to osmosis. This is based on the assumption that the produce has a lower water potential than the hypotonic solution, leading to water absorption by the produce. Conversely, when immersed in hypertonic solutions such as .6 molarity sucrose, .8 molarity sucrose and 1.0 molarity sucrose, we predict that the produce will lose weight. This is because the higher concentration of solute in the solution results in a higher water potential compared to the produce cells.
Unified and Paraphrased: In this study, the water potential of five different types of produce will be compared to each other. Any differences in the water potential of the produce will be observed. Additionally, the water potential of the produce will be compared to the water potential of pure water, which is 0.
Materials used:
The experiment utilized the following materials: russet potato, Gala apple, Imperator carrot, Naval orange, and Pascal celery obtained from Smiths grocery and Dr. Thirwell’s classroom. Additionally, there were six solutions for each produce type: distilled water, 0.2-molarity sucrose, 0.4-molarity sucrose, 0.6-molarity sucrose, 0.8-molarity sucrose, and 1.0-molarity sucrose. The sucrose molarities were determined using a gram scale and a graduated cylinder to measure the ingredients. To hold the produce samples in the six solutions for five trials and five produce types, 150 56.7 gram plastic cups were used. A graduated syringe was employed to measure 24 ml of each sucrose solution and distilled water. The initial and final mass of each produce sample was measured using a digital gram scale, while a serrated knife was used for cutting the produce.
Aluminum foil is used to protect each plastic cup from light. Tweezers are used for transferring produce samples to and from the cups, preventing hand oils from affecting the sample’s mass. The procedure is as follows:
1. Obtain all materials and wash hands.
2. Cut 30 pieces of each type of fruit or vegetable, small enough to fit in a 56.7 gram plastic cup (6 pieces per trial).
3. Weigh the initial mass of each produce sample using a digital gram scale and record it in a table.
4. Use tweezers to place the recorded produce samples in their designated cups.Fill each of the six cups per trial with 24 ml of distilled water, 0.2-molarity sucrose, 0.4-molarity sucrose, 0.6-molarity sucrose, 0.8-molarity sucrose, and 1.0- molarity sucrose.
5.Cover each plastic cup with aluminum foil to prevent solution evaporation.
6.Let the thirty cups for each type of produce sit for two days.
7.After two days, remove the aluminum foil.Record final mass of each produce sample using digital gram scale.Transport fruit or vegetable using tweezers.Remove excess liquids from sample by dabbing it on paper towel.
8.Record final masses in a table.
9. Calculate the percentage change in mass for each cup, determine the averages and standard deviation for the six solutions of each fruit or vegetable variable.
10. Create a line graph with the averages for each fruit or vegetable and indicate the point where the percentage change in mass intersects the x-axis (sucrose molarity) – this intersection represents the sucrose concentration with a water potential equivalent to the produce’s water potential.
11. Note down the water potential of each produce and compare and contrast them.
Qualitative Observations:
At the start of the experiment, all produce and sucrose solutions looked normal. Nevertheless, a small amount of mold was discovered inside the bottle holding the 0.2-molarity sucrose solution. Throughout the experiment, the produce samples were placed in assigned cups and covered with aluminum foil for control purposes. The aluminum foil remained in place until after two days of soaking when it was time to weigh the produce.
After conducting the experiment, it was observed that most of the produce, specifically apples, became soft and turgid in the solutions of distilled water, 0.2 M sucrose, and 0.4 M sucrose. This observation was supported by an increase in weight (in grams) of the majority of the produce in those solutions. Additionally, mold growth on produce, particularly potatoes, was noticed in the solutions of 0.6 M sucrose, 0.8 M sucrose, and 1.0 M sucrose. It is worth mentioning that all potato samples in the 1.0 M sucrose solution experienced an average mass loss of 25 percent.
Analysis of data:
The analysis of the data shows that the control, distilled water, and 0.2-molarity sucrose solutions all caused an increase in mass for the potato samples. However, there was a significant decrease in mass for the potato samples when exposed to 0.4-molarity, 0.6-molarity, 0.8-molarity, and 1.0-molarity sucrose solutions. The results are unusual because there was an average gain of 3.3% mass in the 0.2-molarity sucrose solution and only a 2% gain in mass with distilled water for the potato samples. One possible explanation for this peculiar data is the high standard deviations observed: values of 19.9, 4, 2.6, 9.6, 5.8, and 6 respectively indicate a large variation compared to the average percent change in mass for each trial.
Graphing the average values of the potato samples on a graphing calculator allowed us to determine their approximate water potential at .25 bars per unit volume compared to pure water.
The carrots experienced an overall increase in mass when placed in distilled water (with a standard deviation of .6), as well as both .2-molarity sucrose (with a standard deviation of 1) and .4-molarity sucrose (with three standard deviations) solutions on average.This suggests that their approximate water potential is .43 bars.
The carrot samples showed a decrease in mass in the solutions of 0.6M sucrose, 0.8M sucrose, and 1.0M sucrose. However, the standard deviations of these data points (4, 13, and 13.7) suggest that they may not be reliable or conclusive.
On the other hand, the orange samples generally gained mass in distilled water, 0.2M sucrose, 0.4M sucrose, 0.6M sucrose, and 0.8M sucrose but lost a small amount of mass in 1.0M sucrose.
The unexpected outcomes from the orange samples surprised us because our hypothesis indicated similar water potentials for each variable. Considering all types of produce, we would expect oranges to have the highest water potential due to their somewhat saturated state.
Our analysis of average points showed that the Navel orange has a water potential of approximately .94 bars, significantly lower than pure water (0). The standard deviations for our orange samples ranged from .73 to 3.6 and increased with sucrose concentration. Both the standard error of the means and the standard deviations support the water potential of .94 bars for oranges.
On the other hand, celery samples displayed an increase in mass when immersed in distilled water and solutions with sucrose concentrations of 0.2-molarity and 0.4-molarity. However, they experienced a loss in mass when exposed to solutions ranging from 0.6-molarity to 1.0-molarity sucrose concentrations. The standard deviations for celery varied between 1.5 and 5.6, following a similar order as before. By examining the graph depicting trial averages for celery samples, we estimated their water potential to be around .46 bars.
The apple samples gained weight in distilled water, 0.2M sucrose solution, and 0.4M sucrose solution but lost weight in 0.6M sucrose, 0.8M sucrose, and 1.0M sucrose solutions. Based on the graph provided, the estimated water potential of the apple samples is approximately .51 bars. The low standard deviations (2.6, 3.2, 2.1, 1.7, 1.4, 4.7) at the x-axis intercept further support a water potential of around .51 bars.
Possible experimental errors:
Due to using produce from two different sources, there may be slight differences in water potential of each sample. The sucrose solutions were replaced midway through the experiment and there may have been a ratio difference in the second batch, potentially affecting data accuracy. When measuring the final mass of the samples, there might have been residue left on some, leading to inaccurate data. Two different digital gram scales were used, which could have caused slight variations in mass recordings.
During the process of transferring the produce from the scale to their respective cups and adding the solutions, certain produce items may have been exposed to dry air for longer durations, potentially altering the data. Furthermore, it should be noted that some of the produce utilized, particularly the potatoes, were significantly older than others, resulting in potential cell death and possibly contributing to the inconsistent data observed with the potatoes. Additionally, the measurement of produce sample masses was conducted hastily, increasing the likelihood of errors in data recording. In conclusion,
Based on our hypothesis, the water potential of various fruits and vegetables was expected to differ by a maximum of .05 bars. Additionally, we anticipated that all produce would gain weight when placed in solutions of distilled water, .2-molarity sucrose, and .4-molarity sucrose. However, as the concentration of sucrose increased to .6-molarity, .8-molarity, and 1.0-molarity, we predicted that the produce would experience weight loss. Our experimental results did not completely support our hypothesis since not all variables followed the expected patterns. While certain samples such as carrot, celery, and apple displayed the anticipated trends. The calculated water potentials for each produce variable are: Potato (.25 bars), carrot (.43 bars), celery (.46 bars), apple (.51 bars), and orange (.94 bars). Contrary to our hypothesis, there is significant variation in the calculated water potentials with relatively high standard deviations within each produce variable.
Further experimentation:
To enhance the experiment on ‘The effect of various fruit and vegetable cell membranes on their water potential,’ it is suggested that several improvements be taken into account. One possibility is to examine the water potential of multiple vegetables belonging to the same family, such as cucumber, melon, pumpkin, squash, mallow, and courgette. By focusing on one family, the experiment becomes more specific compared to testing numerous types of fruit and vegetables. Additionally, testing a single vegetable family may lead to less variability and more supportive data.
Ensure the accuracy of the measured mass of the produce sample by weighing it multiple times and removing any excess residue. Select a specific part of the produce, such as cores or skin, for experimentation. Examine the produce cells before and after soaking them in specific sucrose molarities under a microscope to compare their shape before and after osmosis. After using these specific sucrose molarities, consider varying them from 0 to 1.0 in increments of 0.1 to observe more precise trends in data. Prepare enough sucrose molarities to avoid the need for replacements, thus reducing the potential for mistakes during solution preparation. Take note of the temperature in Celsius to accurately calculate water potential on paper.
